update

public/courses/prog-intro/homeworks/sum/SumDouble.java

@@ -3,25 +3,25 @@
 public class SumDouble {
 
     public static void main(String[] args) {
-        double sum = 0; // int -> double
+        double sum = 0;
         for (String argument : args) {
             StringBuilder number = new StringBuilder();
             for (char c : argument.toCharArray()) {
                 if (!Character.isWhitespace(c)) {
                     number.append(c);
                 } else {
-                    if (!number.isEmpty()) {
-                        sum += Double.parseDouble(number.toString()); // Integer.parseInt -> Double.parseDouble())
-                    }
+                    sum += parseNumber(number); // method call
                     number = new StringBuilder();
                 }
             }
 
-            if (!number.isEmpty()) {
-                sum += Double.parseDouble(number.toString()); // Integer.parseInt() -> Double.parseDouble()
-            }
+            sum += parseNumber(number); // method call
         }
 
         System.out.println(sum);
     }
+
+    static double parseNumber(StringBuilder number) {
+        return number.isEmpty() ? 0.0 : Double.parseDouble(number.toString());
+    }
 }

public/courses/prog-intro/homeworks/sum/SumHex.java

@@ -0,0 +1,38 @@
+// SumHex.java
+
+public class SumHex {
+
+    public static void main(String[] args) {
+        int sum = 0;
+        for (String argument : args) {
+            StringBuilder number = new StringBuilder();
+            for (char c : argument.toCharArray()) {
+                if (!Character.isWhitespace(c)) {
+                    number.append(c);
+                } else {
+                    sum += parseNumber(number);
+                    number = new StringBuilder();
+                }
+            }
+
+            sum += parseNumber(number);
+        }
+
+        System.out.println(sum);
+    }
+
+    static long parseNumber(StringBuilder number) {
+        if (!number.isEmpty()) {
+            String numberString = number.toString();
+            if (
+                numberString.startsWith("0x") || numberString.startsWith("0X")
+            ) {
+                return Long.parseLong(numberString.substring(2), 16);
+            } else {
+                return Integer.parseInt(numberString);
+            }
+        } else {
+            return 0;
+        }
+    }
+}

public/courses/prog-intro/homeworks/sum/index.html

@@ -35,7 +35,7 @@ java Sum 1 2 -3 Expected output: 0." /><link rel="canonical" href="http://localh
 Examples:
 java Sum 1 2 3 Expected output: 6.
 java Sum 1 2 -3 Expected output: 0.">
-  <meta itemprop="wordCount" content="2236">
+  <meta itemprop="wordCount" content="2000">
   <meta name="twitter:card" content="summary">
   <meta name="twitter:title" content="Sum">
   <meta name="twitter:description" content="Task You need to create a Sum class which will sum integers from command line arguments and output the sum to console.
@@ -196,6 +196,7 @@ java Sum 1 2 -3 Expected output: 0.">
     href="/courses/prog-intro/homeworks/sum/"
     
   >Sum
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
     </a>
   
     <ul class='hx:flex hx:flex-col hx:gap-1 hx:relative hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:dark:before:bg-neutral-800 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:pr-3 hx:rtl:before:right-0 hx:ltr:ml-3 hx:rtl:mr-3'><li>
@@ -204,15 +205,35 @@ java Sum 1 2 -3 Expected output: 0.">
                 class="hx:flex hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [word-break:break-word] hx:cursor-pointer [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] hx:contrast-more:border hx:gap-2 hx:before:opacity-25 hx:before:content-['#'] hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:text-gray-900 hx:contrast-more:dark:text-gray-50 hx:contrast-more:border-transparent hx:contrast-more:hover:border-gray-900 hx:contrast-more:dark:hover:border-gray-50"
               >Solution</a>
             </li>
-          <li>
-              <a
-                href="#solution-1"
-                class="hx:flex hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [word-break:break-word] hx:cursor-pointer [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] hx:contrast-more:border hx:gap-2 hx:before:opacity-25 hx:before:content-['#'] hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:text-gray-900 hx:contrast-more:dark:text-gray-50 hx:contrast-more:border-transparent hx:contrast-more:hover:border-gray-900 hx:contrast-more:dark:hover:border-gray-50"
-              >Solution</a>
-            </li>
           </ul>
   
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/sumdouble/"
+    
+  >SumDouble
+    </a>
               
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/sumhex/"
+    
+  >SumHex
+    </a>
+              
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/sumlongoctal/"
+    
+  >SumLongOctal
+    </a>
+              
+            </li></ul>
+      </div>
             </li></ul>
       </div>
             </li><li class="hx:flex hx:flex-col "><a
@@ -280,8 +301,35 @@ java Sum 1 2 -3 Expected output: 0.">
     href="/courses/prog-intro/homeworks/sum/"
     
   >Sum
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/sumdouble/"
+    
+  >SumDouble
     </a>
               
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/sumhex/"
+    
+  >SumHex
+    </a>
+              
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/sumlongoctal/"
+    
+  >SumLongOctal
+    </a>
+              
+            </li></ul>
+      </div>
             </li></ul>
       </div>
             </li><li class="hx:flex hx:flex-col "><a
@@ -371,10 +419,6 @@ java Sum 1 2 -3 Expected output: 0.">
       <li class="hx:my-2 hx:scroll-my-6 hx:scroll-py-6">
         <a class="hx:font-medium hx:inline-block hx:text-gray-500 hx:hover:text-gray-900 hx:dark:text-gray-400 hx:dark:hover:text-gray-300 hx:contrast-more:text-gray-900 hx:contrast-more:underline hx:contrast-more:dark:text-gray-50 hx:w-full hx:break-words" href="#solution">Solution
         </a>
-      </li></ul><ul>
-      <li class="hx:my-2 hx:scroll-my-6 hx:scroll-py-6">
-        <a class="hx:font-medium hx:inline-block hx:text-gray-500 hx:hover:text-gray-900 hx:dark:text-gray-400 hx:dark:hover:text-gray-300 hx:contrast-more:text-gray-900 hx:contrast-more:underline hx:contrast-more:dark:text-gray-50 hx:w-full hx:break-words" href="#solution-1">Solution
-        </a>
       </li></ul>
       <div class="hx:mt-8 hx:border-t hx:bg-white hx:pt-8 hx:shadow-[0_-12px_16px_white] hx:dark:bg-dark hx:dark:shadow-[0_-12px_16px_#111] hx:sticky hx:bottom-0 hx:flex hx:flex-col hx:items-start hx:gap-2 hx:pb-8 hx:border-gray-200 hx:dark:border-neutral-800 hx:contrast-more:border-t hx:contrast-more:border-neutral-400 hx:contrast-more:shadow-none hx:contrast-more:dark:border-neutral-400">
         <button aria-hidden="true" id="backToTop" onClick="scrollUp();" class="hx:cursor-pointer hx:transition-all hx:duration-75 hx:opacity-0 hx:text-xs hx:font-medium hx:text-gray-500 hx:hover:text-gray-900 hx:dark:text-gray-400 hx:dark:hover:text-gray-100 hx:contrast-more:text-gray-800 hx:contrast-more:dark:text-gray-50">
@@ -1215,77 +1259,6 @@ java Sum 1 2 -3 Expected output: 0.">
 </div>
 </div>
 <p>This is it! The code is ready.</p>
-<hr>
-<p>Below are some modifications to the code for deeper understanding of basic language constructions primarily data types. It is always advised to try completing them by yourself before reading the solution. Modifications progress in difficulty from easy to hard.</p>
-<h1>SumDouble</h1><ul>
-<li>Input data is 64-bytes floating point numbers.</li>
-<li>Class should be named <code>SumDouble</code>.</li>
-</ul>
-<h2>Solution<span class="hx:absolute hx:-mt-20" id="solution-1"></span>
-    <a href="#solution-1" class="subheading-anchor" aria-label="Permalink for this section"></a></h2><p>This modification is fairly easy. All we need to do is to replace all integers with floating point numbers.</p>
-<div class="hx:overflow-x-auto hx:mt-6 hx:flex hx:flex-col hx:rounded-lg hx:border hx:py-4 hx:px-4 hx:border-gray-200 hx:contrast-more:border-current hx:contrast-more:dark:border-current hx:border-blue-200 hx:bg-blue-100 hx:text-blue-900 hx:dark:border-blue-200/30 hx:dark:bg-blue-900/30 hx:dark:text-blue-200">
-  <p class="hx:flex hx:items-center hx:font-medium"><svg height=16px class="hx:inline-block hx:align-middle hx:mr-2" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor" aria-hidden="true"><path stroke-linecap="round" stroke-linejoin="round" d="M13 16h-1v-4h-1m1-4h.01M21 12a9 9 0 11-18 0 9 9 0 0118 0z"/></svg>Note</p>
-
-  <div class="hx:w-full hx:min-w-0 hx:leading-7">
-    <div class="hx:mt-6 hx:leading-7 hx:first:mt-0"><p>Here we can see all of the benefits of using <code>Character.isWhitespace()</code>, because if we had had for example a set of digits and check if the character is in that set we would need to add <code>.</code> (point) to that set to count floating point numbers as well.</p></div>
-  </div>
-</div>
-<p>So here&rsquo;s the updated code</p>
-<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
-
-<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#75715e">// SumDouble.java</span>
-</span></span><span style="display:flex;"><span>
-</span></span><span style="display:flex;"><span><span style="color:#66d9ef">public</span> <span style="color:#66d9ef">class</span> <span style="color:#a6e22e">SumDouble</span> {
-</span></span><span style="display:flex;"><span>
-</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">public</span> <span style="color:#66d9ef">static</span> <span style="color:#66d9ef">void</span> <span style="color:#a6e22e">main</span>(String<span style="color:#f92672">[]</span> args) {
-</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">double</span> sum <span style="color:#f92672">=</span> 0; <span style="color:#75715e">// int -&gt; double</span>
-</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">for</span> (String argument : args) {
-</span></span><span style="display:flex;"><span>            StringBuilder number <span style="color:#f92672">=</span> <span style="color:#66d9ef">new</span> StringBuilder();
-</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">for</span> (<span style="color:#66d9ef">char</span> c : argument.<span style="color:#a6e22e">toCharArray</span>()) {
-</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>Character.<span style="color:#a6e22e">isWhitespace</span>(c)) {
-</span></span><span style="display:flex;"><span>                    number.<span style="color:#a6e22e">append</span>(c);
-</span></span><span style="display:flex;"><span>                } <span style="color:#66d9ef">else</span> {
-</span></span><span style="display:flex;"><span>                    <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>number.<span style="color:#a6e22e">isEmpty</span>()) {
-</span></span><span style="display:flex;"><span>                        sum <span style="color:#f92672">+=</span> Double.<span style="color:#a6e22e">parseDouble</span>(number.<span style="color:#a6e22e">toString</span>()); <span style="color:#75715e">// Integer.parseInt -&gt; Double.parseDouble())</span>
-</span></span><span style="display:flex;"><span>                    }
-</span></span><span style="display:flex;"><span>                    number <span style="color:#f92672">=</span> <span style="color:#66d9ef">new</span> StringBuilder();
-</span></span><span style="display:flex;"><span>                }
-</span></span><span style="display:flex;"><span>            }
-</span></span><span style="display:flex;"><span>
-</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>number.<span style="color:#a6e22e">isEmpty</span>()) {
-</span></span><span style="display:flex;"><span>                sum <span style="color:#f92672">+=</span> Double.<span style="color:#a6e22e">parseDouble</span>(number.<span style="color:#a6e22e">toString</span>()); <span style="color:#75715e">// Integer.parseInt() -&gt; Double.parseDouble()</span>
-</span></span><span style="display:flex;"><span>            }
-</span></span><span style="display:flex;"><span>        }
-</span></span><span style="display:flex;"><span>
-</span></span><span style="display:flex;"><span>        System.<span style="color:#a6e22e">out</span>.<span style="color:#a6e22e">println</span>(sum);
-</span></span><span style="display:flex;"><span>    }
-</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
-  <button
-    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
-    title="Copy code"
-  >
-    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
-<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
-  </button>
-</div>
-</div>
-<p>This code will work fine and pass all the tests, but can we improve it?</p>
-<p>We can see repeating part of code here</p>
-<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
-
-<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>number.<span style="color:#a6e22e">isEmpty</span>()) {
-</span></span><span style="display:flex;"><span>    sum <span style="color:#f92672">+=</span> Double.<span style="color:#a6e22e">parseDouble</span>(number.<span style="color:#a6e22e">toString</span>()); <span style="color:#75715e">// Integer.parseInt() -&gt; Double.parseDouble()</span>
-</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
-  <button
-    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
-    title="Copy code"
-  >
-    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
-<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
-  </button>
-</div>
-</div>
-<hr>
 
         </div>
         <div class="hx:mt-16"></div>

public/courses/prog-intro/homeworks/sum/sumdouble/SumDouble.java

@@ -0,0 +1,27 @@
+// SumDouble.java
+
+public class SumDouble {
+
+    public static void main(String[] args) {
+        double sum = 0;
+        for (String argument : args) {
+            StringBuilder number = new StringBuilder();
+            for (char c : argument.toCharArray()) {
+                if (!Character.isWhitespace(c)) {
+                    number.append(c);
+                } else {
+                    sum += parseNumber(number); // method call
+                    number = new StringBuilder();
+                }
+            }
+
+            sum += parseNumber(number); // method call
+        }
+
+        System.out.println(sum);
+    }
+
+    static double parseNumber(StringBuilder number) {
+        return number.isEmpty() ? 0.0 : Double.parseDouble(number.toString());
+    }
+}

public/courses/prog-intro/homeworks/sum/sumdouble/index.html

@@ -0,0 +1,624 @@
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+  <meta name="description" content="Below are some modifications to the code for deeper understanding of basic language constructions primarily data types. It is always advised to try completing them by yourself before reading the solution. Modifications progress in difficulty from easy to hard.
+Task Input data is 64-bytes floating point numbers. Class should be named SumDouble. Solution This modification is fairly easy. All we need to do is to replace all integers with floating point numbers." /><link rel="canonical" href="http://localhost:1313/courses/prog-intro/homeworks/sum/sumdouble/" itemprop="url" />
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+    
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+  <meta itemprop="description" content="Below are some modifications to the code for deeper understanding of basic language constructions primarily data types. It is always advised to try completing them by yourself before reading the solution. Modifications progress in difficulty from easy to hard.
+Task Input data is 64-bytes floating point numbers. Class should be named SumDouble. Solution This modification is fairly easy. All we need to do is to replace all integers with floating point numbers.">
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+  <meta name="twitter:description" content="Below are some modifications to the code for deeper understanding of basic language constructions primarily data types. It is always advised to try completing them by yourself before reading the solution. Modifications progress in difficulty from easy to hard.
+Task Input data is 64-bytes floating point numbers. Class should be named SumDouble. Solution This modification is fairly easy. All we need to do is to replace all integers with floating point numbers.">
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+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a><div class="hx:ltr:pr-0 hx:overflow-hidden">
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+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/spring-boot/"
+    
+  >Spring Boot
+    </a>
+              
+            </li><li class="hx:flex hx:flex-col open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/"
+    
+  >Introduction to Programming in Java
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/"
+    
+  >Homeworks
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/"
+    
+  >Sum
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hextra-sidebar-active-item hx:bg-primary-100 hx:font-semibold hx:text-primary-800 hx:contrast-more:border hx:contrast-more:border-primary-500 hx:dark:bg-primary-400/10 hx:dark:text-primary-600 hx:contrast-more:dark:border-primary-500"
+    href="/courses/prog-intro/homeworks/sum/sumdouble/"
+    
+  >SumDouble
+    </a>
+  
+    <ul class='hx:flex hx:flex-col hx:gap-1 hx:relative hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:dark:before:bg-neutral-800 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:pr-3 hx:rtl:before:right-0 hx:ltr:ml-3 hx:rtl:mr-3'><li>
+              <a
+                href="#solution"
+                class="hx:flex hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [word-break:break-word] hx:cursor-pointer [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] hx:contrast-more:border hx:gap-2 hx:before:opacity-25 hx:before:content-['#'] hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:text-gray-900 hx:contrast-more:dark:text-gray-50 hx:contrast-more:border-transparent hx:contrast-more:hover:border-gray-900 hx:contrast-more:dark:hover:border-gray-50"
+              >Solution</a>
+            </li>
+          </ul>
+  
+              
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/sumhex/"
+    
+  >SumHex
+    </a>
+              
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/sumlongoctal/"
+    
+  >SumLongOctal
+    </a>
+              
+            </li></ul>
+      </div>
+            </li></ul>
+      </div>
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/lectures/"
+    
+  >Lectures
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/lectures/intro/"
+    
+  >Lecture 1. Introduction
+    </a>
+              
+            </li></ul>
+      </div>
+            </li></ul>
+      </div>
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/paradigms/"
+    
+  >Paradgims of Programming
+    </a>
+              
+            </li></ul>
+      </div></li>
+    </ul>
+
+    <ul class="hx:flex hx:flex-col hx:gap-1 hx:max-md:hidden">
+        
+          <li class=""><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/spring-boot/"
+    
+  >Spring Boot
+    </a></li>
+          <li class="open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/"
+    
+  >Introduction to Programming in Java
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a><div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/"
+    
+  >Homeworks
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/"
+    
+  >Sum
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hextra-sidebar-active-item hx:bg-primary-100 hx:font-semibold hx:text-primary-800 hx:contrast-more:border hx:contrast-more:border-primary-500 hx:dark:bg-primary-400/10 hx:dark:text-primary-600 hx:contrast-more:dark:border-primary-500"
+    href="/courses/prog-intro/homeworks/sum/sumdouble/"
+    
+  >SumDouble
+    </a>
+              
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/sumhex/"
+    
+  >SumHex
+    </a>
+              
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/sumlongoctal/"
+    
+  >SumLongOctal
+    </a>
+              
+            </li></ul>
+      </div>
+            </li></ul>
+      </div>
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/lectures/"
+    
+  >Lectures
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/lectures/intro/"
+    
+  >Lecture 1. Introduction
+    </a>
+              
+            </li></ul>
+      </div>
+            </li></ul>
+      </div></li>
+          <li class=""><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/paradigms/"
+    
+  >Paradgims of Programming
+    </a></li>
+        
+      </ul>
+    </div>
+  
+  
+    <div class="  hx:sticky hx:bottom-0 hx:max-h-(--menu-height) hx:bg-white hx:dark:bg-dark hx:mx-4 hx:py-4 hx:shadow-[0_-12px_16px_#fff] hx:flex hx:items-center hx:gap-2 hx:border-gray-200 hx:dark:border-neutral-800 hx:dark:shadow-[0_-12px_16px_#111] hx:contrast-more:border-neutral-400 hx:contrast-more:shadow-none hx:contrast-more:dark:shadow-none hx:border-t" data-toggle-animation="show"><div class="hx:flex hx:grow hx:flex-col"><div class="hx:flex hx:justify-items-start hx:group" data-theme="light">
+  <button
+    title="Change theme"
+    data-state="closed"
+    data-location="bottom"
+    class="hextra-theme-toggle hx:cursor-pointer hx:rounded-md hx:text-left hx:font-medium hx:h-7 hx:px-2 hx:text-xs hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:font-medium hx:text-gray-600 hx:transition-colors hx:dark:text-gray-400 hx:grow"
+    type="button"
+    aria-label="Change theme"
+  >
+    <div class="hx:flex hx:items-center hx:gap-2 hx:capitalize"><svg height=12 class="hx:group-data-[theme=dark]:hidden hx:group-data-[theme=system]:hidden" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor" aria-hidden="true"><path stroke-linecap="round" stroke-linejoin="round" d="M12 3v1m0 16v1m9-9h-1M4 12H3m15.364 6.364l-.707-.707M6.343 6.343l-.707-.707m12.728 0l-.707.707M6.343 17.657l-.707.707M16 12a4 4 0 11-8 0 4 4 0 018 0z"/></svg><span class="hx:group-data-[theme=dark]:hidden hx:group-data-[theme=system]:hidden">Light</span><svg height=12 class="hx:group-data-[theme=light]:hidden hx:group-data-[theme=system]:hidden" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor" aria-hidden="true"><path stroke-linecap="round" stroke-linejoin="round" d="M20.354 15.354A9 9 0 018.646 3.646 9.003 9.003 0 0012 21a9.003 9.003 0 008.354-5.646z"/></svg><span class="hx:group-data-[theme=light]:hidden hx:group-data-[theme=system]:hidden">Dark</span><svg height=12 class="hx:group-data-[theme=dark]:hidden hx:group-data-[theme=light]:hidden" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"  fill="currentColor">
+  <path d="M 11.996094,2 C 6.4986225,2.0192368 2.03125,6.5024993 2.03125,12 c 0,5.497501 4.4673725,9.980763 9.964844,10 H 12 12.0039 c 5.497471,-0.01924 9.964844,-4.502499 9.964844,-10 0,-5.4975007 -4.467373,-9.9807632 -9.964844,-10 H 12 Z M 12,4 c 4.417218,0.017598 7.96875,3.5822356 7.96875,8 0,4.417764 -3.551532,7.982402 -7.96875,8 z" />
+</svg>
+<span class="hx:group-data-[theme=dark]:hidden hx:group-data-[theme=light]:hidden">System</span></div>
+  </button>
+  <ul
+    class="hextra-theme-toggle-options hx:hidden hx:z-20 hx:max-h-64 hx:overflow-auto hx:rounded-md hx:ring-1 hx:ring-black/5 hx:bg-white hx:py-1 hx:text-sm hx:shadow-lg hx:dark:ring-white/20 hx:dark:bg-neutral-800"
+    style="position: fixed; inset: auto auto 0px 0px; margin: 0px; min-width: 100px;"
+    data-theme="light"
+  >
+    <li class="hx:flex hx:flex-col">
+      <p
+        data-item="light"
+        class="hx:text-gray-800 hx:dark:text-gray-100 hx:hover:bg-primary-50 hx:hover:text-primary-600 hx:hover:dark:bg-primary-500/10 hx:hover:dark:text-primary-600 hx:relative hx:cursor-pointer hx:whitespace-nowrap hx:py-1.5 hx:transition-colors hx:ltr:pl-3 hx:ltr:pr-9 hx:rtl:pr-3 hx:rtl:pl-9"
+      >
+        Light
+         <span class="hx:absolute hx:inset-y-0 hx:flex hx:items-center hx:ltr:right-3 hx:rtl:left-3 hx:group-data-[theme=dark]:hidden hx:group-data-[theme=system]:hidden"><svg height=1em width=1em xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor" aria-hidden="true"><path stroke-linecap="round" stroke-linejoin="round" d="M5 13l4 4L19 7"/></svg></span>
+      </p>
+    </li>
+    <li class="hx:flex hx:flex-col">
+      <p
+        data-item="dark"
+        class="hx:text-gray-800 hx:dark:text-gray-100 hx:hover:bg-primary-50 hx:hover:text-primary-600 hx:hover:dark:bg-primary-500/10 hx:hover:dark:text-primary-600 hx:relative hx:cursor-pointer hx:whitespace-nowrap hx:py-1.5 hx:transition-colors hx:ltr:pl-3 hx:ltr:pr-9 hx:rtl:pr-3 hx:rtl:pl-9"
+      >
+        Dark
+         <span class="hx:absolute hx:inset-y-0 hx:flex hx:items-center hx:ltr:right-3 hx:rtl:left-3 hx:group-data-[theme=light]:hidden hx:group-data-[theme=system]:hidden"><svg height=1em width=1em xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor" aria-hidden="true"><path stroke-linecap="round" stroke-linejoin="round" d="M5 13l4 4L19 7"/></svg></span>
+      </p>
+    </li>
+    <li class="hx:flex hx:flex-col">
+      <p
+        data-item="system"
+        class="hx:text-gray-800 hx:dark:text-gray-100 hx:hover:bg-primary-50 hx:hover:text-primary-600 hx:hover:dark:bg-primary-500/10 hx:hover:dark:text-primary-600 hx:relative hx:cursor-pointer hx:whitespace-nowrap hx:py-1.5 hx:transition-colors hx:ltr:pl-3 hx:ltr:pr-9 hx:rtl:pr-3 hx:rtl:pl-9"
+      >
+        System
+         <span class="hx:absolute hx:inset-y-0 hx:flex hx:items-center hx:ltr:right-3 hx:rtl:left-3 hx:group-data-[theme=dark]:hidden hx:group-data-[theme=light]:hidden"><svg height=1em width=1em xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor" aria-hidden="true"><path stroke-linecap="round" stroke-linejoin="round" d="M5 13l4 4L19 7"/></svg></span>
+      </p>
+    </li>
+  </ul>
+</div></div></div></aside>
+    
+<nav class="hextra-toc hx:order-last hx:hidden hx:w-64 hx:shrink-0 hx:xl:block hx:print:hidden hx:px-4" aria-label="table of contents">
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+    <article class="hx:w-full hx:break-words hx:flex hx:min-h-[calc(100vh-var(--navbar-height))] hx:min-w-0 hx:justify-center hx:pb-8 hx:pr-[calc(env(safe-area-inset-right)-1.5rem)]">
+      <main class="hx:w-full hx:min-w-0 hx:max-w-6xl hx:px-6 hx:pt-4 hx:md:px-12">
+        
+        <div class="content">
+          <h1>SumDouble</h1>
+          <p>Below are some modifications to the code for deeper understanding of basic language constructions primarily data types. It is always advised to try completing them by yourself before reading the solution. Modifications progress in difficulty from easy to hard.</p>
+<h1>Task</h1><ul>
+<li>Input data is 64-bytes floating point numbers.</li>
+<li>Class should be named <code>SumDouble</code>.</li>
+</ul>
+<h2>Solution<span class="hx:absolute hx:-mt-20" id="solution"></span>
+    <a href="#solution" class="subheading-anchor" aria-label="Permalink for this section"></a></h2><p>This modification is fairly easy. All we need to do is to replace all integers with floating point numbers.</p>
+<div class="hx:overflow-x-auto hx:mt-6 hx:flex hx:flex-col hx:rounded-lg hx:border hx:py-4 hx:px-4 hx:border-gray-200 hx:contrast-more:border-current hx:contrast-more:dark:border-current hx:border-blue-200 hx:bg-blue-100 hx:text-blue-900 hx:dark:border-blue-200/30 hx:dark:bg-blue-900/30 hx:dark:text-blue-200">
+  <p class="hx:flex hx:items-center hx:font-medium"><svg height=16px class="hx:inline-block hx:align-middle hx:mr-2" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor" aria-hidden="true"><path stroke-linecap="round" stroke-linejoin="round" d="M13 16h-1v-4h-1m1-4h.01M21 12a9 9 0 11-18 0 9 9 0 0118 0z"/></svg>Note</p>
+
+  <div class="hx:w-full hx:min-w-0 hx:leading-7">
+    <div class="hx:mt-6 hx:leading-7 hx:first:mt-0"><p>Here we can see all of the benefits of using <code>Character.isWhitespace()</code>, because if we had had for example a set of digits and check if the character is in that set we would need to add <code>.</code> (point) to that set to count floating point numbers as well.</p></div>
+  </div>
+</div>
+<p>So here&rsquo;s the updated code</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#75715e">// SumDouble.java</span>
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span><span style="color:#66d9ef">public</span> <span style="color:#66d9ef">class</span> <span style="color:#a6e22e">SumDouble</span> {
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">public</span> <span style="color:#66d9ef">static</span> <span style="color:#66d9ef">void</span> <span style="color:#a6e22e">main</span>(String<span style="color:#f92672">[]</span> args) {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">double</span> sum <span style="color:#f92672">=</span> 0; <span style="color:#75715e">// int -&gt; double</span>
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">for</span> (String argument : args) {
+</span></span><span style="display:flex;"><span>            StringBuilder number <span style="color:#f92672">=</span> <span style="color:#66d9ef">new</span> StringBuilder();
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">for</span> (<span style="color:#66d9ef">char</span> c : argument.<span style="color:#a6e22e">toCharArray</span>()) {
+</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>Character.<span style="color:#a6e22e">isWhitespace</span>(c)) {
+</span></span><span style="display:flex;"><span>                    number.<span style="color:#a6e22e">append</span>(c);
+</span></span><span style="display:flex;"><span>                } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>                    <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>number.<span style="color:#a6e22e">isEmpty</span>()) {
+</span></span><span style="display:flex;"><span>                        sum <span style="color:#f92672">+=</span> Double.<span style="color:#a6e22e">parseDouble</span>(number.<span style="color:#a6e22e">toString</span>()); <span style="color:#75715e">// Integer.parseInt -&gt; Double.parseDouble())</span>
+</span></span><span style="display:flex;"><span>                    }
+</span></span><span style="display:flex;"><span>                    number <span style="color:#f92672">=</span> <span style="color:#66d9ef">new</span> StringBuilder();
+</span></span><span style="display:flex;"><span>                }
+</span></span><span style="display:flex;"><span>            }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>number.<span style="color:#a6e22e">isEmpty</span>()) {
+</span></span><span style="display:flex;"><span>                sum <span style="color:#f92672">+=</span> Double.<span style="color:#a6e22e">parseDouble</span>(number.<span style="color:#a6e22e">toString</span>()); <span style="color:#75715e">// Integer.parseInt() -&gt; Double.parseDouble()</span>
+</span></span><span style="display:flex;"><span>            }
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>        System.<span style="color:#a6e22e">out</span>.<span style="color:#a6e22e">println</span>(sum);
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>This code will work fine and pass all the tests, but can we improve it?</p>
+<p>We can see repeating part of code here</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>number.<span style="color:#a6e22e">isEmpty</span>()) {
+</span></span><span style="display:flex;"><span>    sum <span style="color:#f92672">+=</span> Double.<span style="color:#a6e22e">parseDouble</span>(number.<span style="color:#a6e22e">toString</span>()); <span style="color:#75715e">// Integer.parseInt() -&gt; Double.parseDouble()</span>
+</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>And if we want to change it, we would need to do so in 2 places. That&rsquo;s considered bad practice. You can read about <em><strong>DRY</strong></em> principle <a href="https://en.wikipedia.org/wiki/Don%27t_repeat_yourself"target="_blank" rel="noopener">here</a>.</p>
+<p>So let&rsquo;s extract this code to its own method called <code>parseNumber</code>.</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#66d9ef">static</span> <span style="color:#66d9ef">double</span> <span style="color:#a6e22e">parseNumber</span>(StringBuilder number) {
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">return</span> number.<span style="color:#a6e22e">isEmpty</span>() <span style="color:#f92672">?</span> 0.<span style="color:#a6e22e">0</span> : Double.<span style="color:#a6e22e">parseDouble</span>(number.<span style="color:#a6e22e">toString</span>());
+</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>It&rsquo;s a <code>static</code> method, because we can&rsquo;t call a non-static method from a static context which is <code>main</code> method. If we didn&rsquo;t have <code>static</code> keyword in <code>parseNumber</code> method we would have gotten an error.</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-bash" data-lang="bash"><span style="display:flex;"><span>$ javac SumDouble.java
+</span></span><span style="display:flex;"><span>SumDouble.java:13: error: non-static method parseNumber<span style="color:#f92672">(</span>StringBuilder<span style="color:#f92672">)</span> cannot be referenced from a static context
+</span></span><span style="display:flex;"><span>                    sum <span style="color:#f92672">+=</span> parseNumber<span style="color:#f92672">(</span>number<span style="color:#f92672">)</span>; // method call
+</span></span><span style="display:flex;"><span>                           ^
+</span></span><span style="display:flex;"><span>SumDouble.java:18: error: non-static method parseNumber<span style="color:#f92672">(</span>StringBuilder<span style="color:#f92672">)</span> cannot be referenced from a static context
+</span></span><span style="display:flex;"><span>            sum <span style="color:#f92672">+=</span> parseNumber<span style="color:#f92672">(</span>number<span style="color:#f92672">)</span>; // method call
+</span></span><span style="display:flex;"><span>                   ^
+</span></span><span style="display:flex;"><span><span style="color:#ae81ff">2</span> errors</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>Also we need to discuss the ternary operator. It is a shortened form of <code>if</code>-statement. Its structure looks like this</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span>(<span style="color:#75715e">/* condition */</span>) <span style="color:#f92672">?</span> (<span style="color:#75715e">/* do if true */</span>) : (<span style="color:#75715e">/* do if false */</span>) </span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>First argument states a condition. If the condition is <code>true</code>, then the second block gets executed. If the condition if <code>false</code>, then the third block gets executed. It will work the same as</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#66d9ef">if</span> (<span style="color:#75715e">/* condition */</span>) {
+</span></span><span style="display:flex;"><span>    <span style="color:#75715e">/* do if true */</span>
+</span></span><span style="display:flex;"><span>} <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>    <span style="color:#75715e">/* do if false */</span>
+</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>So here&rsquo;s the updated code</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#75715e">// SumDouble.java</span>
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span><span style="color:#66d9ef">public</span> <span style="color:#66d9ef">class</span> <span style="color:#a6e22e">SumDouble</span> {
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">public</span> <span style="color:#66d9ef">static</span> <span style="color:#66d9ef">void</span> <span style="color:#a6e22e">main</span>(String<span style="color:#f92672">[]</span> args) {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">double</span> sum <span style="color:#f92672">=</span> 0;
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">for</span> (String argument : args) {
+</span></span><span style="display:flex;"><span>            StringBuilder number <span style="color:#f92672">=</span> <span style="color:#66d9ef">new</span> StringBuilder();
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">for</span> (<span style="color:#66d9ef">char</span> c : argument.<span style="color:#a6e22e">toCharArray</span>()) {
+</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>Character.<span style="color:#a6e22e">isWhitespace</span>(c)) {
+</span></span><span style="display:flex;"><span>                    number.<span style="color:#a6e22e">append</span>(c);
+</span></span><span style="display:flex;"><span>                } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>                    sum <span style="color:#f92672">+=</span> parseNumber(number); <span style="color:#75715e">// method call</span>
+</span></span><span style="display:flex;"><span>                    number <span style="color:#f92672">=</span> <span style="color:#66d9ef">new</span> StringBuilder();
+</span></span><span style="display:flex;"><span>                }
+</span></span><span style="display:flex;"><span>            }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>            sum <span style="color:#f92672">+=</span> parseNumber(number); <span style="color:#75715e">// method call</span>
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>        System.<span style="color:#a6e22e">out</span>.<span style="color:#a6e22e">println</span>(sum);
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">static</span> <span style="color:#66d9ef">double</span> <span style="color:#a6e22e">parseNumber</span>(StringBuilder number) {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">return</span> number.<span style="color:#a6e22e">isEmpty</span>() <span style="color:#f92672">?</span> 0.<span style="color:#a6e22e">0</span> : Double.<span style="color:#a6e22e">parseDouble</span>(number.<span style="color:#a6e22e">toString</span>());
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
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+    title="Copy code"
+  >
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public/courses/prog-intro/homeworks/sum/sumhex/SumHex.java

@@ -0,0 +1,38 @@
+// SumHex.java
+
+public class SumHex {
+
+    public static void main(String[] args) {
+        int sum = 0;
+        for (String argument : args) {
+            StringBuilder number = new StringBuilder();
+            for (char c : argument.toCharArray()) {
+                if (!Character.isWhitespace(c)) {
+                    number.append(c);
+                } else {
+                    sum += parseNumber(number);
+                    number = new StringBuilder();
+                }
+            }
+
+            sum += parseNumber(number);
+        }
+
+        System.out.println(sum);
+    }
+
+    static long parseNumber(StringBuilder number) {
+        if (!number.isEmpty()) {
+            String numberString = number.toString();
+            if (
+                numberString.startsWith("0x") || numberString.startsWith("0X")
+            ) {
+                return Long.parseLong(numberString.substring(2), 16);
+            } else {
+                return Integer.parseInt(numberString);
+            }
+        } else {
+            return 0;
+        }
+    }
+}

public/courses/prog-intro/homeworks/sum/sumhex/index.html

@@ -0,0 +1,753 @@
+<!DOCTYPE html>
+<html lang="en" dir="ltr"><head><script src="/livereload.js?mindelay=10&amp;v=2&amp;port=1313&amp;path=livereload" data-no-instant defer></script>
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+<title>SumHex – CodeJava</title>
+  <meta name="description" content="Task The input is in decimal and hexadecimal numbers Hexademical numbers has the prefix 0x The input is case insensitive Class should be named SumHex Solution This modification doesn’t seem too complicated either.
+Let’s modify our initial Sum.java and apply all our improvements from a previous modification. (A good exercise would be to try doing that yourself and then comeback to check)
+// SumHex.java public class SumHex { public static void main(String[] args) { int sum = 0; for (String argument : args) { StringBuilder number = new StringBuilder(); for (char c : argument.toCharArray()) { if (!Character.isWhitespace(c)) { number.append(c); } else { sum &#43;= parseNumber(number); number = new StringBuilder(); } } sum &#43;= parseNumber(number); } System.out.println(sum); } static int parseNumber(StringBuilder number) { return number.isEmpty() ? 0 : Integer.parseInt(number.toString()); } } Note" /><link rel="canonical" href="http://localhost:1313/courses/prog-intro/homeworks/sum/sumhex/" itemprop="url" />
+
+<meta property="og:title" content="SumHex">
+<meta
+  property="og:description"
+  content="
+    
+      Learn Java programming
+    
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+    website
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+
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+  <meta itemprop="name" content="SumHex">
+  <meta itemprop="description" content="Task The input is in decimal and hexadecimal numbers Hexademical numbers has the prefix 0x The input is case insensitive Class should be named SumHex Solution This modification doesn’t seem too complicated either.
+Let’s modify our initial Sum.java and apply all our improvements from a previous modification. (A good exercise would be to try doing that yourself and then comeback to check)
+// SumHex.java public class SumHex { public static void main(String[] args) { int sum = 0; for (String argument : args) { StringBuilder number = new StringBuilder(); for (char c : argument.toCharArray()) { if (!Character.isWhitespace(c)) { number.append(c); } else { sum &#43;= parseNumber(number); number = new StringBuilder(); } } sum &#43;= parseNumber(number); } System.out.println(sum); } static int parseNumber(StringBuilder number) { return number.isEmpty() ? 0 : Integer.parseInt(number.toString()); } } Note">
+  <meta itemprop="wordCount" content="822">
+  <meta name="twitter:card" content="summary">
+  <meta name="twitter:title" content="SumHex">
+  <meta name="twitter:description" content="Task The input is in decimal and hexadecimal numbers Hexademical numbers has the prefix 0x The input is case insensitive Class should be named SumHex Solution This modification doesn’t seem too complicated either.
+Let’s modify our initial Sum.java and apply all our improvements from a previous modification. (A good exercise would be to try doing that yourself and then comeback to check)
+// SumHex.java public class SumHex { public static void main(String[] args) { int sum = 0; for (String argument : args) { StringBuilder number = new StringBuilder(); for (char c : argument.toCharArray()) { if (!Character.isWhitespace(c)) { number.append(c); } else { sum &#43;= parseNumber(number); number = new StringBuilder(); } } sum &#43;= parseNumber(number); } System.out.println(sum); } static int parseNumber(StringBuilder number) { return number.isEmpty() ? 0 : Integer.parseInt(number.toString()); } } Note">
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+    >
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+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/spring-boot/"
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+    href="/courses/prog-intro/"
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+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/"
+    
+  >Sum
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/sumdouble/"
+    
+  >SumDouble
+    </a>
+              
+            </li><li class="hx:flex hx:flex-col open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hextra-sidebar-active-item hx:bg-primary-100 hx:font-semibold hx:text-primary-800 hx:contrast-more:border hx:contrast-more:border-primary-500 hx:dark:bg-primary-400/10 hx:dark:text-primary-600 hx:contrast-more:dark:border-primary-500"
+    href="/courses/prog-intro/homeworks/sum/sumhex/"
+    
+  >SumHex
+    </a>
+  
+    <ul class='hx:flex hx:flex-col hx:gap-1 hx:relative hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:dark:before:bg-neutral-800 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:pr-3 hx:rtl:before:right-0 hx:ltr:ml-3 hx:rtl:mr-3'><li>
+              <a
+                href="#solution"
+                class="hx:flex hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [word-break:break-word] hx:cursor-pointer [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] hx:contrast-more:border hx:gap-2 hx:before:opacity-25 hx:before:content-['#'] hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:text-gray-900 hx:contrast-more:dark:text-gray-50 hx:contrast-more:border-transparent hx:contrast-more:hover:border-gray-900 hx:contrast-more:dark:hover:border-gray-50"
+              >Solution</a>
+            </li>
+          </ul>
+  
+              
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/sumlongoctal/"
+    
+  >SumLongOctal
+    </a>
+              
+            </li></ul>
+      </div>
+            </li></ul>
+      </div>
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/lectures/"
+    
+  >Lectures
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/lectures/intro/"
+    
+  >Lecture 1. Introduction
+    </a>
+              
+            </li></ul>
+      </div>
+            </li></ul>
+      </div>
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/paradigms/"
+    
+  >Paradgims of Programming
+    </a>
+              
+            </li></ul>
+      </div></li>
+    </ul>
+
+    <ul class="hx:flex hx:flex-col hx:gap-1 hx:max-md:hidden">
+        
+          <li class=""><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/spring-boot/"
+    
+  >Spring Boot
+    </a></li>
+          <li class="open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/"
+    
+  >Introduction to Programming in Java
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a><div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/"
+    
+  >Homeworks
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/"
+    
+  >Sum
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/sumdouble/"
+    
+  >SumDouble
+    </a>
+              
+            </li><li class="hx:flex hx:flex-col open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hextra-sidebar-active-item hx:bg-primary-100 hx:font-semibold hx:text-primary-800 hx:contrast-more:border hx:contrast-more:border-primary-500 hx:dark:bg-primary-400/10 hx:dark:text-primary-600 hx:contrast-more:dark:border-primary-500"
+    href="/courses/prog-intro/homeworks/sum/sumhex/"
+    
+  >SumHex
+    </a>
+              
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/sumlongoctal/"
+    
+  >SumLongOctal
+    </a>
+              
+            </li></ul>
+      </div>
+            </li></ul>
+      </div>
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/lectures/"
+    
+  >Lectures
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/lectures/intro/"
+    
+  >Lecture 1. Introduction
+    </a>
+              
+            </li></ul>
+      </div>
+            </li></ul>
+      </div></li>
+          <li class=""><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/paradigms/"
+    
+  >Paradgims of Programming
+    </a></li>
+        
+      </ul>
+    </div>
+  
+  
+    <div class="  hx:sticky hx:bottom-0 hx:max-h-(--menu-height) hx:bg-white hx:dark:bg-dark hx:mx-4 hx:py-4 hx:shadow-[0_-12px_16px_#fff] hx:flex hx:items-center hx:gap-2 hx:border-gray-200 hx:dark:border-neutral-800 hx:dark:shadow-[0_-12px_16px_#111] hx:contrast-more:border-neutral-400 hx:contrast-more:shadow-none hx:contrast-more:dark:shadow-none hx:border-t" data-toggle-animation="show"><div class="hx:flex hx:grow hx:flex-col"><div class="hx:flex hx:justify-items-start hx:group" data-theme="light">
+  <button
+    title="Change theme"
+    data-state="closed"
+    data-location="bottom"
+    class="hextra-theme-toggle hx:cursor-pointer hx:rounded-md hx:text-left hx:font-medium hx:h-7 hx:px-2 hx:text-xs hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:font-medium hx:text-gray-600 hx:transition-colors hx:dark:text-gray-400 hx:grow"
+    type="button"
+    aria-label="Change theme"
+  >
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+        
+        <div class="content">
+          <h1>SumHex</h1>
+          <h1>Task</h1><ul>
+<li>The input is in decimal and hexadecimal numbers</li>
+<li>Hexademical numbers has the prefix <code>0x</code></li>
+<li>The input is case insensitive</li>
+<li>Class should be named <code>SumHex</code></li>
+</ul>
+<h2>Solution<span class="hx:absolute hx:-mt-20" id="solution"></span>
+    <a href="#solution" class="subheading-anchor" aria-label="Permalink for this section"></a></h2><p>This modification doesn&rsquo;t seem too complicated either.</p>
+<p>Let&rsquo;s modify our initial <code>Sum.java</code> and apply all our improvements from a previous modification. (A good exercise would be to try doing that yourself and then comeback to check)</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#75715e">// SumHex.java</span>
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span><span style="color:#66d9ef">public</span> <span style="color:#66d9ef">class</span> <span style="color:#a6e22e">SumHex</span> {
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">public</span> <span style="color:#66d9ef">static</span> <span style="color:#66d9ef">void</span> <span style="color:#a6e22e">main</span>(String<span style="color:#f92672">[]</span> args) {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">int</span> sum <span style="color:#f92672">=</span> 0;
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">for</span> (String argument : args) {
+</span></span><span style="display:flex;"><span>            StringBuilder number <span style="color:#f92672">=</span> <span style="color:#66d9ef">new</span> StringBuilder();
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">for</span> (<span style="color:#66d9ef">char</span> c : argument.<span style="color:#a6e22e">toCharArray</span>()) {
+</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>Character.<span style="color:#a6e22e">isWhitespace</span>(c)) {
+</span></span><span style="display:flex;"><span>                    number.<span style="color:#a6e22e">append</span>(c);
+</span></span><span style="display:flex;"><span>                } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>                    sum <span style="color:#f92672">+=</span> parseNumber(number);
+</span></span><span style="display:flex;"><span>                    number <span style="color:#f92672">=</span> <span style="color:#66d9ef">new</span> StringBuilder();
+</span></span><span style="display:flex;"><span>                }
+</span></span><span style="display:flex;"><span>            }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>            sum <span style="color:#f92672">+=</span> parseNumber(number);
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>        System.<span style="color:#a6e22e">out</span>.<span style="color:#a6e22e">println</span>(sum);
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">static</span> <span style="color:#66d9ef">int</span> <span style="color:#a6e22e">parseNumber</span>(StringBuilder number) {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">return</span> number.<span style="color:#a6e22e">isEmpty</span>() <span style="color:#f92672">?</span> 0 : Integer.<span style="color:#a6e22e">parseInt</span>(number.<span style="color:#a6e22e">toString</span>());
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<div class="hx:overflow-x-auto hx:mt-6 hx:flex hx:flex-col hx:rounded-lg hx:border hx:py-4 hx:px-4 hx:border-gray-200 hx:contrast-more:border-current hx:contrast-more:dark:border-current hx:border-blue-200 hx:bg-blue-100 hx:text-blue-900 hx:dark:border-blue-200/30 hx:dark:bg-blue-900/30 hx:dark:text-blue-200">
+  <p class="hx:flex hx:items-center hx:font-medium"><svg height=16px class="hx:inline-block hx:align-middle hx:mr-2" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor" aria-hidden="true"><path stroke-linecap="round" stroke-linejoin="round" d="M13 16h-1v-4h-1m1-4h.01M21 12a9 9 0 11-18 0 9 9 0 0118 0z"/></svg>Note</p>
+
+  <div class="hx:w-full hx:min-w-0 hx:leading-7">
+    <div class="hx:mt-6 hx:leading-7 hx:first:mt-0"><p>The importance of these changes, is that in all further modifications we will only be changing our parseNumber method and leaving <code>main</code> method almost unchanged. The only modifications to <code>main</code> would be changing the data type of <code>sum</code>.</p></div>
+  </div>
+</div>
+<p>Now <code>parseNumber</code> thinks that every number is decimal, but we don&rsquo;t know what to do with hexadecimal numbers. Let&rsquo;s try that</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-bash" data-lang="bash"><span style="display:flex;"><span>$ java SumHex 0x1 0x2 0x3
+</span></span><span style="display:flex;"><span>Exception in thread <span style="color:#e6db74">&#34;main&#34;</span> java.lang.NumberFormatException: For input string: <span style="color:#e6db74">&#34;0x1&#34;</span>
+</span></span><span style="display:flex;"><span>	at java.base/java.lang.NumberFormatException.forInputString<span style="color:#f92672">(</span>NumberFormatException.java:67<span style="color:#f92672">)</span>
+</span></span><span style="display:flex;"><span>	at java.base/java.lang.Integer.parseInt<span style="color:#f92672">(</span>Integer.java:662<span style="color:#f92672">)</span>
+</span></span><span style="display:flex;"><span>	at java.base/java.lang.Integer.parseInt<span style="color:#f92672">(</span>Integer.java:778<span style="color:#f92672">)</span>
+</span></span><span style="display:flex;"><span>	at SumHex.parseNumber<span style="color:#f92672">(</span>SumHex.java:25<span style="color:#f92672">)</span>
+</span></span><span style="display:flex;"><span>	at SumHex.main<span style="color:#f92672">(</span>SumHex.java:18<span style="color:#f92672">)</span></span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>So we need to split decimal and hexadecimal processing inside <code>parseNumber</code>. Our code would look something like this.</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#66d9ef">static</span> <span style="color:#66d9ef">int</span> <span style="color:#a6e22e">parseNumber</span>(StringBuilder number) {
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>number.<span style="color:#a6e22e">isEmpty</span>()) {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> (<span style="color:#75715e">/* number is hexadecimal */</span>) {
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> <span style="color:#75715e">/* parse hexadecimal */</span>; 
+</span></span><span style="display:flex;"><span>        } <span style="color:#66d9ef">else</span> { <span style="color:#75715e">// if the number if decimal</span>
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> Integer.<span style="color:#a6e22e">parseInt</span>(number.<span style="color:#a6e22e">toString</span>());
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>    
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">return</span> 0;
+</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>Here we have 2 major questions:</p>
+<ul>
+<li>How to check if the number is hexadecimal?</li>
+<li>How to parse the hexadecimal number?</li>
+</ul>
+<p>We can answer the 1st question, because we know that hexadecimal number starts with <code>&quot;0x&quot;</code>. And we know that the input is not case sensitive, so <code>&quot;0X&quot;</code> is also a valid option.</p>
+<p>So we can change our <em>pseude-code</em> like this</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#66d9ef">static</span> <span style="color:#66d9ef">int</span> <span style="color:#a6e22e">parseNumber</span>(StringBuilder number) {
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>number.<span style="color:#a6e22e">isEmpty</span>()) {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> (<span style="color:#75715e">/* number starts with &#34;0x&#34; or &#34;0X&#34; */</span>) {
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> <span style="color:#75715e">/* parse hexadecimal */</span>; 
+</span></span><span style="display:flex;"><span>        } <span style="color:#66d9ef">else</span> { <span style="color:#75715e">// if the number is decimal</span>
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> Integer.<span style="color:#a6e22e">parseInt</span>(number.<span style="color:#a6e22e">toString</span>());
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>    
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">return</span> 0;
+</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>But how to check if the string starts with some prefix? There is a <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#startsWith-java.lang.String-"target="_blank" rel="noopener"><code>String.startsWith(String prefix)</code></a> that returns <code>true</code> if the string starts with <code>prefix</code> and <code>false</code> otherwise.</p>
+<p>So we can change our code using this information.</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#66d9ef">static</span> <span style="color:#66d9ef">int</span> <span style="color:#a6e22e">parseNumber</span>(StringBuilder number) {
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>number.<span style="color:#a6e22e">isEmpty</span>()) {
+</span></span><span style="display:flex;"><span>        String numberString <span style="color:#f92672">=</span> number.<span style="color:#a6e22e">toString</span>();
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> (
+</span></span><span style="display:flex;"><span>            numberString.<span style="color:#a6e22e">startsWith</span>(<span style="color:#e6db74">&#34;0x&#34;</span>) <span style="color:#f92672">||</span> 
+</span></span><span style="display:flex;"><span>            numberString.<span style="color:#a6e22e">startsWith</span>(<span style="color:#e6db74">&#34;0X&#34;</span>)
+</span></span><span style="display:flex;"><span>        ) {
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> <span style="color:#75715e">/* parse hexadecimal */</span>; 
+</span></span><span style="display:flex;"><span>        } <span style="color:#66d9ef">else</span> { <span style="color:#75715e">// if the number is decimal</span>
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> Integer.<span style="color:#a6e22e">parseInt</span>(number.<span style="color:#a6e22e">toString</span>());
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>    
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">return</span> 0;
+</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<div class="hx:overflow-x-auto hx:mt-6 hx:flex hx:flex-col hx:rounded-lg hx:border hx:py-4 hx:px-4 hx:border-gray-200 hx:contrast-more:border-current hx:contrast-more:dark:border-current hx:border-blue-200 hx:bg-blue-100 hx:text-blue-900 hx:dark:border-blue-200/30 hx:dark:bg-blue-900/30 hx:dark:text-blue-200">
+  <p class="hx:flex hx:items-center hx:font-medium"><svg height=16px class="hx:inline-block hx:align-middle hx:mr-2" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor" aria-hidden="true"><path stroke-linecap="round" stroke-linejoin="round" d="M13 16h-1v-4h-1m1-4h.01M21 12a9 9 0 11-18 0 9 9 0 0118 0z"/></svg>Note</p>
+
+  <div class="hx:w-full hx:min-w-0 hx:leading-7">
+    <div class="hx:mt-6 hx:leading-7 hx:first:mt-0"><p><code>||</code> here is a logical <em><strong>or</strong></em>.</p></div>
+  </div>
+</div>
+<p>We still have one problem. How to parse the hexadecimal number?</p>
+<p>Using <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/Integer.html#parseInt-java.lang.String-int-"target="_blank" rel="noopener"><code>Integer.parseInt()</code></a> method. It turnes out, that it has the second argument <code>radix</code> where we can specify the base of the numerical system (in our case it&rsquo;s <code>16</code>).</p>
+<p>So our code will look like this.</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#66d9ef">static</span> <span style="color:#66d9ef">int</span> <span style="color:#a6e22e">parseNumber</span>(StringBuilder number) {
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">if</span> (number.<span style="color:#a6e22e">isEmpty</span>()) {
+</span></span><span style="display:flex;"><span>        String numberString <span style="color:#f92672">=</span> number.<span style="color:#a6e22e">toString</span>();
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> (
+</span></span><span style="display:flex;"><span>            numberString.<span style="color:#a6e22e">startsWith</span>(<span style="color:#e6db74">&#34;0x&#34;</span>) <span style="color:#f92672">||</span> 
+</span></span><span style="display:flex;"><span>            numberString.<span style="color:#a6e22e">startsWith</span>(<span style="color:#e6db74">&#34;0X&#34;</span>)
+</span></span><span style="display:flex;"><span>        ) {
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> Integer.<span style="color:#a6e22e">parseInt</span>(numberString.<span style="color:#a6e22e">substring</span>(2), 16); 
+</span></span><span style="display:flex;"><span>        } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> Integer.<span style="color:#a6e22e">parseInt</span>(numberString);
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>    
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">return</span> 0;
+</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<div class="hx:overflow-x-auto hx:mt-6 hx:flex hx:flex-col hx:rounded-lg hx:border hx:py-4 hx:px-4 hx:border-gray-200 hx:contrast-more:border-current hx:contrast-more:dark:border-current hx:border-blue-200 hx:bg-blue-100 hx:text-blue-900 hx:dark:border-blue-200/30 hx:dark:bg-blue-900/30 hx:dark:text-blue-200">
+  <p class="hx:flex hx:items-center hx:font-medium"><svg height=16px class="hx:inline-block hx:align-middle hx:mr-2" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor" aria-hidden="true"><path stroke-linecap="round" stroke-linejoin="round" d="M13 16h-1v-4h-1m1-4h.01M21 12a9 9 0 11-18 0 9 9 0 0118 0z"/></svg>Note</p>
+
+  <div class="hx:w-full hx:min-w-0 hx:leading-7">
+    <div class="hx:mt-6 hx:leading-7 hx:first:mt-0"><p>Here we used <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#substring-int-"target="_blank" rel="noopener"><code>String.substring(int beginIndex)</code></a> method to cut off first two symbols (<code>&quot;0x&quot;</code>/<code>&quot;0X&quot;</code>) in order for <code>parseInt</code> to parse number correctly and not give us exceptions. In our case <code>beginIndex = 2</code> because it&rsquo;s the first index of the substring that we want to get. Remember that <em><strong>indexing starts with 0</strong></em> (not 1).</p></div>
+  </div>
+</div>
+<div class="hx:overflow-x-auto hx:mt-6 hx:flex hx:flex-col hx:rounded-lg hx:border hx:py-4 hx:px-4 hx:border-gray-200 hx:contrast-more:border-current hx:contrast-more:dark:border-current hx:border-purple-200 hx:bg-purple-100 hx:text-purple-900 hx:dark:border-purple-200/30 hx:dark:bg-purple-900/30 hx:dark:text-purple-200">
+  <p class="hx:flex hx:items-center hx:font-medium"><svg height=16px class="hx:inline-block hx:align-middle hx:mr-2" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor" aria-hidden="true"><path stroke-linecap="round" stroke-linejoin="round" d="M13 16h-1v-4h-1m1-4h.01M21 12a9 9 0 11-18 0 9 9 0 0118 0z"/></svg>Important</p>
+
+  <div class="hx:w-full hx:min-w-0 hx:leading-7">
+    <div class="hx:mt-6 hx:leading-7 hx:first:mt-0"><p>It&rsquo;s important to know that we can&rsquo;t store all hexadecimal numbers in <code>int</code> data type. Let&rsquo;s look at this example</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-bash" data-lang="bash"><span style="display:flex;"><span>$ java SumHex 0x80000000
+</span></span><span style="display:flex;"><span>Exception in thread <span style="color:#e6db74">&#34;main&#34;</span> java.lang.NumberFormatException: For input string: <span style="color:#e6db74">&#34;80000000&#34;</span> under radix <span style="color:#ae81ff">16</span>
+</span></span><span style="display:flex;"><span>	at java.base/java.lang.NumberFormatException.forInputString<span style="color:#f92672">(</span>NumberFormatException.java:67<span style="color:#f92672">)</span>
+</span></span><span style="display:flex;"><span>	at java.base/java.lang.Integer.parseInt<span style="color:#f92672">(</span>Integer.java:662<span style="color:#f92672">)</span>
+</span></span><span style="display:flex;"><span>	at SumHex.parseNumber<span style="color:#f92672">(</span>SumHex.java:30<span style="color:#f92672">)</span>
+</span></span><span style="display:flex;"><span>	at SumHex.main<span style="color:#f92672">(</span>SumHex.java:18<span style="color:#f92672">)</span> </span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>That&rsquo;s why we will need to use <code>long</code> data type for storing hexademical values.</p></div>
+  </div>
+</div>
+<p>Here&rsquo;s the updated code</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#66d9ef">static</span> <span style="color:#66d9ef">long</span> <span style="color:#a6e22e">parseNumber</span>(StringBuilder number) { <span style="color:#75715e">// int -&gt; long</span>
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>number.<span style="color:#a6e22e">isEmpty</span>()) {
+</span></span><span style="display:flex;"><span>        String numberString <span style="color:#f92672">=</span> number.<span style="color:#a6e22e">toString</span>();
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> (numberString.<span style="color:#a6e22e">startsWith</span>(<span style="color:#e6db74">&#34;0x&#34;</span>) <span style="color:#f92672">||</span> numberString.<span style="color:#a6e22e">startsWith</span>(<span style="color:#e6db74">&#34;0X&#34;</span>)) {
+</span></span><span style="display:flex;"><span>            <span style="color:#75715e">// Integer.parseInt -&gt; Long.parseLong</span>
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> Long.<span style="color:#a6e22e">parseLong</span>(numberString.<span style="color:#a6e22e">substring</span>(2), 16);
+</span></span><span style="display:flex;"><span>        } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> Integer.<span style="color:#a6e22e">parseInt</span>(numberString);
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>    } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">return</span> 0;
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>Let&rsquo;s present the full solution</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#75715e">// SumHex.java</span>
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span><span style="color:#66d9ef">public</span> <span style="color:#66d9ef">class</span> <span style="color:#a6e22e">SumHex</span> {
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">public</span> <span style="color:#66d9ef">static</span> <span style="color:#66d9ef">void</span> <span style="color:#a6e22e">main</span>(String<span style="color:#f92672">[]</span> args) {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">int</span> sum <span style="color:#f92672">=</span> 0;
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">for</span> (String argument : args) {
+</span></span><span style="display:flex;"><span>            StringBuilder number <span style="color:#f92672">=</span> <span style="color:#66d9ef">new</span> StringBuilder();
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">for</span> (<span style="color:#66d9ef">char</span> c : argument.<span style="color:#a6e22e">toCharArray</span>()) {
+</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>Character.<span style="color:#a6e22e">isWhitespace</span>(c)) {
+</span></span><span style="display:flex;"><span>                    number.<span style="color:#a6e22e">append</span>(c);
+</span></span><span style="display:flex;"><span>                } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>                    sum <span style="color:#f92672">+=</span> parseNumber(number);
+</span></span><span style="display:flex;"><span>                    number <span style="color:#f92672">=</span> <span style="color:#66d9ef">new</span> StringBuilder();
+</span></span><span style="display:flex;"><span>                }
+</span></span><span style="display:flex;"><span>            }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>            sum <span style="color:#f92672">+=</span> parseNumber(number);
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>        System.<span style="color:#a6e22e">out</span>.<span style="color:#a6e22e">println</span>(sum);
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">static</span> <span style="color:#66d9ef">long</span> <span style="color:#a6e22e">parseNumber</span>(StringBuilder number) {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>number.<span style="color:#a6e22e">isEmpty</span>()) {
+</span></span><span style="display:flex;"><span>            String numberString <span style="color:#f92672">=</span> number.<span style="color:#a6e22e">toString</span>();
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">if</span> (numberString.<span style="color:#a6e22e">startsWith</span>(<span style="color:#e6db74">&#34;0x&#34;</span>) <span style="color:#f92672">||</span> numberString.<span style="color:#a6e22e">startsWith</span>(<span style="color:#e6db74">&#34;0X&#34;</span>)) {
+</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">return</span> Long.<span style="color:#a6e22e">parseLong</span>(numberString.<span style="color:#a6e22e">substring</span>(2), 16);
+</span></span><span style="display:flex;"><span>            } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">return</span> Integer.<span style="color:#a6e22e">parseInt</span>(numberString);
+</span></span><span style="display:flex;"><span>            }
+</span></span><span style="display:flex;"><span>        } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> 0;
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
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+<div class="hx:overflow-x-auto hx:mt-6 hx:flex hx:flex-col hx:rounded-lg hx:border hx:py-4 hx:px-4 hx:border-gray-200 hx:contrast-more:border-current hx:contrast-more:dark:border-current hx:border-purple-200 hx:bg-purple-100 hx:text-purple-900 hx:dark:border-purple-200/30 hx:dark:bg-purple-900/30 hx:dark:text-purple-200">
+  <p class="hx:flex hx:items-center hx:font-medium"><svg height=16px class="hx:inline-block hx:align-middle hx:mr-2" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor" aria-hidden="true"><path stroke-linecap="round" stroke-linejoin="round" d="M13 16h-1v-4h-1m1-4h.01M21 12a9 9 0 11-18 0 9 9 0 0118 0z"/></svg>Important</p>
+
+  <div class="hx:w-full hx:min-w-0 hx:leading-7">
+    <div class="hx:mt-6 hx:leading-7 hx:first:mt-0"><p>Notice, that we didn&rsquo;t change <code>main</code> method at all, because we have a separate function handling parsing. That&rsquo;s a good sign because our <code>main</code> method doesn&rsquo;t know what number parsing algorithm is used and therefore not dependent on it.</p></div>
+  </div>
+</div>
+
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public/courses/prog-intro/homeworks/sum/sumlongoctal/SumLongOctal.java

@@ -0,0 +1,42 @@
+// SumLongOctal.java
+
+import java.math.BigInteger;
+
+public class SumLongOctal {
+
+    public static void main(String[] args) {
+        long sum = 0;
+        for (String argument : args) {
+            StringBuilder number = new StringBuilder();
+            for (char c : argument.toCharArray()) {
+                if (!Character.isWhitespace(c)) {
+                    number.append(c);
+                } else {
+                    sum += parseNumber(number);
+                    number = new StringBuilder();
+                }
+            }
+
+            sum += parseNumber(number);
+        }
+
+        System.out.println(sum);
+    }
+
+    static long parseNumber(StringBuilder number) {
+        if (!number.isEmpty()) {
+            String numberString = number.toString();
+            int numberStringLength = numberString.length();
+            if (numberString.endsWith("o") || numberString.endsWith("O")) {
+                return new BigInteger(
+                    number.substring(0, numberStringLength - 1),
+                    8
+                ).longValue();
+            } else {
+                return Long.parseLong(numberString);
+            }
+        } else {
+            return 0;
+        }
+    }
+}

public/courses/prog-intro/homeworks/sum/sumlongoctal/index.html

@@ -0,0 +1,794 @@
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+<title>SumLongOctal – CodeJava</title>
+  <meta name="description" content="Task The input data is in 64 bit decimal numbers Octal numbers has suffix &#34;o&#34; Class should be named SumLongOctal Solution We need to change our parseNumber method yet again. Let’s take a look at it from SumHex modification
+static long parseNumber(StringBuilder number) { if (!number.isEmpty()) { String numberString = number.toString(); if ( numberString.startsWith(&#34;0x&#34;) || numberString.startsWith(&#34;0X&#34;) ) { return Long.parseLong(numberString.substring(2), 16); } else { return Integer.parseInt(numberString); } } else { return 0; } } Let’s adapt our new logic on a concept level" /><link rel="canonical" href="http://localhost:1313/courses/prog-intro/homeworks/sum/sumlongoctal/" itemprop="url" />
+
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+    
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+    
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+  <meta itemprop="name" content="SumLongOctal">
+  <meta itemprop="description" content="Task The input data is in 64 bit decimal numbers Octal numbers has suffix &#34;o&#34; Class should be named SumLongOctal Solution We need to change our parseNumber method yet again. Let’s take a look at it from SumHex modification
+static long parseNumber(StringBuilder number) { if (!number.isEmpty()) { String numberString = number.toString(); if ( numberString.startsWith(&#34;0x&#34;) || numberString.startsWith(&#34;0X&#34;) ) { return Long.parseLong(numberString.substring(2), 16); } else { return Integer.parseInt(numberString); } } else { return 0; } } Let’s adapt our new logic on a concept level">
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+  <meta name="twitter:title" content="SumLongOctal">
+  <meta name="twitter:description" content="Task The input data is in 64 bit decimal numbers Octal numbers has suffix &#34;o&#34; Class should be named SumLongOctal Solution We need to change our parseNumber method yet again. Let’s take a look at it from SumHex modification
+static long parseNumber(StringBuilder number) { if (!number.isEmpty()) { String numberString = number.toString(); if ( numberString.startsWith(&#34;0x&#34;) || numberString.startsWith(&#34;0X&#34;) ) { return Long.parseLong(numberString.substring(2), 16); } else { return Integer.parseInt(numberString); } } else { return 0; } } Let’s adapt our new logic on a concept level">
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+    href="/courses/spring-boot/"
+    
+  >Spring Boot
+    </a>
+              
+            </li><li class="hx:flex hx:flex-col open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/"
+    
+  >Introduction to Programming in Java
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
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+    href="/courses/prog-intro/homeworks/"
+    
+  >Homeworks
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+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/"
+    
+  >Sum
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/sumdouble/"
+    
+  >SumDouble
+    </a>
+              
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/sumhex/"
+    
+  >SumHex
+    </a>
+              
+            </li><li class="hx:flex hx:flex-col open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hextra-sidebar-active-item hx:bg-primary-100 hx:font-semibold hx:text-primary-800 hx:contrast-more:border hx:contrast-more:border-primary-500 hx:dark:bg-primary-400/10 hx:dark:text-primary-600 hx:contrast-more:dark:border-primary-500"
+    href="/courses/prog-intro/homeworks/sum/sumlongoctal/"
+    
+  >SumLongOctal
+    </a>
+  
+    <ul class='hx:flex hx:flex-col hx:gap-1 hx:relative hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:dark:before:bg-neutral-800 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:pr-3 hx:rtl:before:right-0 hx:ltr:ml-3 hx:rtl:mr-3'><li>
+              <a
+                href="#solution"
+                class="hx:flex hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [word-break:break-word] hx:cursor-pointer [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] hx:contrast-more:border hx:gap-2 hx:before:opacity-25 hx:before:content-['#'] hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:text-gray-900 hx:contrast-more:dark:text-gray-50 hx:contrast-more:border-transparent hx:contrast-more:hover:border-gray-900 hx:contrast-more:dark:hover:border-gray-50"
+              >Solution</a>
+            </li>
+          </ul>
+  
+              
+            </li></ul>
+      </div>
+            </li></ul>
+      </div>
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/lectures/"
+    
+  >Lectures
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/lectures/intro/"
+    
+  >Lecture 1. Introduction
+    </a>
+              
+            </li></ul>
+      </div>
+            </li></ul>
+      </div>
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/paradigms/"
+    
+  >Paradgims of Programming
+    </a>
+              
+            </li></ul>
+      </div></li>
+    </ul>
+
+    <ul class="hx:flex hx:flex-col hx:gap-1 hx:max-md:hidden">
+        
+          <li class=""><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/spring-boot/"
+    
+  >Spring Boot
+    </a></li>
+          <li class="open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/"
+    
+  >Introduction to Programming in Java
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a><div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/"
+    
+  >Homeworks
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/"
+    
+  >Sum
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/sumdouble/"
+    
+  >SumDouble
+    </a>
+              
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/homeworks/sum/sumhex/"
+    
+  >SumHex
+    </a>
+              
+            </li><li class="hx:flex hx:flex-col open"><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hextra-sidebar-active-item hx:bg-primary-100 hx:font-semibold hx:text-primary-800 hx:contrast-more:border hx:contrast-more:border-primary-500 hx:dark:bg-primary-400/10 hx:dark:text-primary-600 hx:contrast-more:dark:border-primary-500"
+    href="/courses/prog-intro/homeworks/sum/sumlongoctal/"
+    
+  >SumLongOctal
+    </a>
+              
+            </li></ul>
+      </div>
+            </li></ul>
+      </div>
+            </li><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/lectures/"
+    
+  >Lectures
+        <span class="hextra-sidebar-collapsible-button"><svg fill="none" viewBox="0 0 24 24" stroke="currentColor" class="hx:h-[18px] hx:min-w-[18px] hx:rounded-xs hx:p-0.5 hx:hover:bg-gray-800/5 hx:dark:hover:bg-gray-100/5"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7" class="hx:origin-center hx:transition-transform hx:rtl:-rotate-180"></path></svg></span>
+    </a>
+              <div class="hx:ltr:pr-0 hx:overflow-hidden">
+        <ul class='hx:relative hx:flex hx:flex-col hx:gap-1 hx:before:absolute hx:before:inset-y-1 hx:before:w-px hx:before:bg-gray-200 hx:before:content-[""] hx:ltr:ml-3 hx:ltr:pl-3 hx:ltr:before:left-0 hx:rtl:mr-3 hx:rtl:pr-3 hx:rtl:before:right-0 hx:dark:before:bg-neutral-800'><li class="hx:flex hx:flex-col "><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/prog-intro/lectures/intro/"
+    
+  >Lecture 1. Introduction
+    </a>
+              
+            </li></ul>
+      </div>
+            </li></ul>
+      </div></li>
+          <li class=""><a
+    class="hx:flex hx:items-center hx:justify-between hx:gap-2 hx:cursor-pointer hx:rounded-sm hx:px-2 hx:py-1.5 hx:text-sm hx:transition-colors [-webkit-tap-highlight-color:transparent] [-webkit-touch-callout:none] [word-break:break-word]
+      hx:text-gray-500 hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:contrast-more:border hx:contrast-more:border-transparent hx:contrast-more:text-gray-900 hx:contrast-more:hover:border-gray-900 hx:dark:text-neutral-400 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:contrast-more:dark:text-gray-50 hx:contrast-more:dark:hover:border-gray-50"
+    href="/courses/paradigms/"
+    
+  >Paradgims of Programming
+    </a></li>
+        
+      </ul>
+    </div>
+  
+  
+    <div class="  hx:sticky hx:bottom-0 hx:max-h-(--menu-height) hx:bg-white hx:dark:bg-dark hx:mx-4 hx:py-4 hx:shadow-[0_-12px_16px_#fff] hx:flex hx:items-center hx:gap-2 hx:border-gray-200 hx:dark:border-neutral-800 hx:dark:shadow-[0_-12px_16px_#111] hx:contrast-more:border-neutral-400 hx:contrast-more:shadow-none hx:contrast-more:dark:shadow-none hx:border-t" data-toggle-animation="show"><div class="hx:flex hx:grow hx:flex-col"><div class="hx:flex hx:justify-items-start hx:group" data-theme="light">
+  <button
+    title="Change theme"
+    data-state="closed"
+    data-location="bottom"
+    class="hextra-theme-toggle hx:cursor-pointer hx:rounded-md hx:text-left hx:font-medium hx:h-7 hx:px-2 hx:text-xs hx:hover:bg-gray-100 hx:hover:text-gray-900 hx:dark:hover:bg-primary-100/5 hx:dark:hover:text-gray-50 hx:font-medium hx:text-gray-600 hx:transition-colors hx:dark:text-gray-400 hx:grow"
+    type="button"
+    aria-label="Change theme"
+  >
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+        
+        <div class="content">
+          <h1>SumLongOctal</h1>
+          <h1>Task</h1><ul>
+<li>The input data is in 64 bit decimal numbers</li>
+<li>Octal numbers has suffix <code>&quot;o&quot;</code></li>
+<li>Class should be named <code>SumLongOctal</code></li>
+</ul>
+<h2>Solution<span class="hx:absolute hx:-mt-20" id="solution"></span>
+    <a href="#solution" class="subheading-anchor" aria-label="Permalink for this section"></a></h2><p>We need to change our <code>parseNumber</code> method yet again. Let&rsquo;s take a look at it from <code>SumHex</code> modification</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#66d9ef">static</span> <span style="color:#66d9ef">long</span> <span style="color:#a6e22e">parseNumber</span>(StringBuilder number) {
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>number.<span style="color:#a6e22e">isEmpty</span>()) {
+</span></span><span style="display:flex;"><span>        String numberString <span style="color:#f92672">=</span> number.<span style="color:#a6e22e">toString</span>();
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> (
+</span></span><span style="display:flex;"><span>            numberString.<span style="color:#a6e22e">startsWith</span>(<span style="color:#e6db74">&#34;0x&#34;</span>) <span style="color:#f92672">||</span> numberString.<span style="color:#a6e22e">startsWith</span>(<span style="color:#e6db74">&#34;0X&#34;</span>)
+</span></span><span style="display:flex;"><span>        ) {
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> Long.<span style="color:#a6e22e">parseLong</span>(numberString.<span style="color:#a6e22e">substring</span>(2), 16);
+</span></span><span style="display:flex;"><span>        } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> Integer.<span style="color:#a6e22e">parseInt</span>(numberString);
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>    } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">return</span> 0;
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>Let&rsquo;s adapt our new logic on a concept level</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#66d9ef">static</span> <span style="color:#66d9ef">long</span> <span style="color:#a6e22e">parseNumber</span>(StringBuilder number) {
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>number.<span style="color:#a6e22e">isEmpty</span>()) {
+</span></span><span style="display:flex;"><span>        String numberString <span style="color:#f92672">=</span> number.<span style="color:#a6e22e">toString</span>();
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">int</span> numberStringLength <span style="color:#f92672">=</span> numberString.<span style="color:#a6e22e">length</span>();
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> (
+</span></span><span style="display:flex;"><span>            <span style="color:#75715e">/* number is octal */</span>
+</span></span><span style="display:flex;"><span>        ) {
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> Long.<span style="color:#a6e22e">parseLong</span>(numberString.<span style="color:#a6e22e">substring</span>(0, numberStringLength <span style="color:#f92672">-</span> 1), 8); <span style="color:#75715e">// 16 -&gt; 8</span>
+</span></span><span style="display:flex;"><span>        } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> Integer.<span style="color:#a6e22e">parseInt</span>(numberString);
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>    } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">return</span> 0;
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>As you can see is that we need to only change method of checking if the number is octal. It&rsquo;s actually fairly easy. With hexadecimal numbers we checked if the number <em><strong>started with</strong></em> <code>&quot;0x&quot;</code> or <code>&quot;0X&quot;</code>. Now we need to check if the number <em><strong>ends with</strong></em> <code>&quot;o&quot;</code> or <code>&quot;O&quot;</code>. To do that we will use <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#endsWith-java.lang.String-"target="_blank" rel="noopener"><code>String.endsWith(String suffix)</code></a> method that checks if the string ends with <code>prefix</code>.</p>
+<p>And also we change <code>16</code> to <code>8</code> here</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#66d9ef">return</span> Long.<span style="color:#a6e22e">parseLong</span>(numberString.<span style="color:#a6e22e">substring</span>(0, numberStringLength <span style="color:#f92672">-</span> 1), 8);</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>Because we are converting from octal, not hexadecimal anymore.</p>
+<div class="hx:overflow-x-auto hx:mt-6 hx:flex hx:flex-col hx:rounded-lg hx:border hx:py-4 hx:px-4 hx:border-gray-200 hx:contrast-more:border-current hx:contrast-more:dark:border-current hx:border-blue-200 hx:bg-blue-100 hx:text-blue-900 hx:dark:border-blue-200/30 hx:dark:bg-blue-900/30 hx:dark:text-blue-200">
+  <p class="hx:flex hx:items-center hx:font-medium"><svg height=16px class="hx:inline-block hx:align-middle hx:mr-2" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor" aria-hidden="true"><path stroke-linecap="round" stroke-linejoin="round" d="M13 16h-1v-4h-1m1-4h.01M21 12a9 9 0 11-18 0 9 9 0 0118 0z"/></svg>Note</p>
+
+  <div class="hx:w-full hx:min-w-0 hx:leading-7">
+    <div class="hx:mt-6 hx:leading-7 hx:first:mt-0"><p>Note, that we alse changed how we crop out the last character of our <code>numberString</code>. First, we introduced new variable <code>numberStringLength</code>, that represents a length of <code>numberString</code> (or number of characters in the string). Then, we take a substring using <code>substring(0, numberStringLength - 1)</code>. We start at first index (<code>0</code>) and go all the way to the second from the end of the string. We use <code>- 1</code> and not <code>- 2</code> because last index is exclusive (meaning it doesn&rsquo;t count).</p></div>
+  </div>
+</div>
+<p>So the code for <code>parseNumber</code> method will be</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#66d9ef">static</span> <span style="color:#66d9ef">long</span> <span style="color:#a6e22e">parseNumber</span>(StringBuilder number) {
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>number.<span style="color:#a6e22e">isEmpty</span>()) {
+</span></span><span style="display:flex;"><span>        String numberString <span style="color:#f92672">=</span> number.<span style="color:#a6e22e">toString</span>();
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">int</span> numberStringLength <span style="color:#f92672">=</span> numberString.<span style="color:#a6e22e">length</span>();
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> (
+</span></span><span style="display:flex;"><span>            numberString.<span style="color:#a6e22e">endsWith</span>(<span style="color:#e6db74">&#34;o&#34;</span>) <span style="color:#f92672">||</span> numberString.<span style="color:#a6e22e">endsWith</span>(<span style="color:#e6db74">&#34;O&#34;</span>)
+</span></span><span style="display:flex;"><span>        ) {
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> Long.<span style="color:#a6e22e">parseLong</span>(numberString.<span style="color:#a6e22e">substring</span>(0, numberStringLength <span style="color:#f92672">-</span> 1), 8); <span style="color:#75715e">// 16 -&gt; 8</span>
+</span></span><span style="display:flex;"><span>        } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> Integer.<span style="color:#a6e22e">parseInt</span>(numberString);
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>    } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">return</span> 0;
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>So the solution would be</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#75715e">// SumLongOctal.java</span>
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span><span style="color:#66d9ef">public</span> <span style="color:#66d9ef">class</span> <span style="color:#a6e22e">SumLongOctal</span> {
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">public</span> <span style="color:#66d9ef">static</span> <span style="color:#66d9ef">void</span> <span style="color:#a6e22e">main</span>(String<span style="color:#f92672">[]</span> args) {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">int</span> sum <span style="color:#f92672">=</span> 0;
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">for</span> (String argument : args) {
+</span></span><span style="display:flex;"><span>            StringBuilder number <span style="color:#f92672">=</span> <span style="color:#66d9ef">new</span> StringBuilder();
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">for</span> (<span style="color:#66d9ef">char</span> c : argument.<span style="color:#a6e22e">toCharArray</span>()) {
+</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>Character.<span style="color:#a6e22e">isWhitespace</span>(c)) {
+</span></span><span style="display:flex;"><span>                    number.<span style="color:#a6e22e">append</span>(c);
+</span></span><span style="display:flex;"><span>                } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>                    sum <span style="color:#f92672">+=</span> parseNumber(number);
+</span></span><span style="display:flex;"><span>                    number <span style="color:#f92672">=</span> <span style="color:#66d9ef">new</span> StringBuilder();
+</span></span><span style="display:flex;"><span>                }
+</span></span><span style="display:flex;"><span>            }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>            sum <span style="color:#f92672">+=</span> parseNumber(number);
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>        System.<span style="color:#a6e22e">out</span>.<span style="color:#a6e22e">println</span>(sum);
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">static</span> <span style="color:#66d9ef">long</span> <span style="color:#a6e22e">parseNumber</span>(StringBuilder number) {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>number.<span style="color:#a6e22e">isEmpty</span>()) {
+</span></span><span style="display:flex;"><span>            String numberString <span style="color:#f92672">=</span> number.<span style="color:#a6e22e">toString</span>();
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">int</span> numberStringLength <span style="color:#f92672">=</span> numberString.<span style="color:#a6e22e">length</span>();
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">if</span> (numberString.<span style="color:#a6e22e">endsWith</span>(<span style="color:#e6db74">&#34;o&#34;</span>) <span style="color:#f92672">||</span> numberString.<span style="color:#a6e22e">endsWith</span>(<span style="color:#e6db74">&#34;O&#34;</span>)) {
+</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">return</span> Long.<span style="color:#a6e22e">parseLong</span>(numberString.<span style="color:#a6e22e">substring</span>(0, numberStringLength <span style="color:#f92672">-</span> ), 8);
+</span></span><span style="display:flex;"><span>            } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">return</span> Integer.<span style="color:#a6e22e">parseInt</span>(numberString);
+</span></span><span style="display:flex;"><span>            }
+</span></span><span style="display:flex;"><span>        } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> 0;
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>Let&rsquo;s try to test it with test like this</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-bash" data-lang="bash"><span style="display:flex;"><span>$ java SumLongOctal <span style="color:#e6db74">&#34; +12345678901234567 &#34;</span>
+</span></span><span style="display:flex;"><span>Exception in thread <span style="color:#e6db74">&#34;main&#34;</span> java.lang.NumberFormatException: For input string: <span style="color:#e6db74">&#34;+12345678901234567&#34;</span>
+</span></span><span style="display:flex;"><span>        at java.base/java.lang.NumberFormatException.forInputString<span style="color:#f92672">(</span>NumberFormatException.java:67<span style="color:#f92672">)</span>
+</span></span><span style="display:flex;"><span>        at java.base/java.lang.Integer.parseInt<span style="color:#f92672">(</span>Integer.java:662<span style="color:#f92672">)</span>
+</span></span><span style="display:flex;"><span>        at java.base/java.lang.Integer.parseInt<span style="color:#f92672">(</span>Integer.java:778<span style="color:#f92672">)</span>
+</span></span><span style="display:flex;"><span>        at sum.SumLongOctal.parseNumber<span style="color:#f92672">(</span>SumLongOctal.java:32<span style="color:#f92672">)</span>
+</span></span><span style="display:flex;"><span>        at sum.SumLongOctal.main<span style="color:#f92672">(</span>SumLongOctal.java:15<span style="color:#f92672">)</span></span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>As you can see we got a <code>NumberFormatException</code>. Here it&rsquo;s not an octal number and it doesn&rsquo;t fit into <code>int</code> data type, so let&rsquo;s change <code>int</code> to <code>long</code> which is bigger.</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#75715e">// SumLongOctal.java</span>
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span><span style="color:#66d9ef">public</span> <span style="color:#66d9ef">class</span> <span style="color:#a6e22e">SumLongOctal</span> {
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">public</span> <span style="color:#66d9ef">static</span> <span style="color:#66d9ef">void</span> <span style="color:#a6e22e">main</span>(String<span style="color:#f92672">[]</span> args) {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">long</span> sum <span style="color:#f92672">=</span> 0; <span style="color:#75715e">// int -&gt; long</span>
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">for</span> (String argument : args) {
+</span></span><span style="display:flex;"><span>            StringBuilder number <span style="color:#f92672">=</span> <span style="color:#66d9ef">new</span> StringBuilder();
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">for</span> (<span style="color:#66d9ef">char</span> c : argument.<span style="color:#a6e22e">toCharArray</span>()) {
+</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>Character.<span style="color:#a6e22e">isWhitespace</span>(c)) {
+</span></span><span style="display:flex;"><span>                    number.<span style="color:#a6e22e">append</span>(c);
+</span></span><span style="display:flex;"><span>                } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>                    sum <span style="color:#f92672">+=</span> parseNumber(number);
+</span></span><span style="display:flex;"><span>                    number <span style="color:#f92672">=</span> <span style="color:#66d9ef">new</span> StringBuilder();
+</span></span><span style="display:flex;"><span>                }
+</span></span><span style="display:flex;"><span>            }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>            sum <span style="color:#f92672">+=</span> parseNumber(number);
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>        System.<span style="color:#a6e22e">out</span>.<span style="color:#a6e22e">println</span>(sum);
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">static</span> <span style="color:#66d9ef">long</span> <span style="color:#a6e22e">parseNumber</span>(StringBuilder number) {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>number.<span style="color:#a6e22e">isEmpty</span>()) {
+</span></span><span style="display:flex;"><span>            String numberString <span style="color:#f92672">=</span> number.<span style="color:#a6e22e">toString</span>();
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">int</span> numberStringLength <span style="color:#f92672">=</span> numberString.<span style="color:#a6e22e">length</span>();
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">if</span> (numberString.<span style="color:#a6e22e">endsWith</span>(<span style="color:#e6db74">&#34;o&#34;</span>) <span style="color:#f92672">||</span> numberString.<span style="color:#a6e22e">endsWith</span>(<span style="color:#e6db74">&#34;O&#34;</span>)) {
+</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">return</span> Long.<span style="color:#a6e22e">parseLong</span>(numberString.<span style="color:#a6e22e">substring</span>(0, numberStringLength <span style="color:#f92672">-</span> 1), 8);
+</span></span><span style="display:flex;"><span>            } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">return</span> Long.<span style="color:#a6e22e">parseLong</span>(numberString); <span style="color:#75715e">// Integer.parseInt(...) -&gt; Long.parseLong(...)</span>
+</span></span><span style="display:flex;"><span>            }
+</span></span><span style="display:flex;"><span>        } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> 0;
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<div class="hx:overflow-x-auto hx:mt-6 hx:flex hx:flex-col hx:rounded-lg hx:border hx:py-4 hx:px-4 hx:border-gray-200 hx:contrast-more:border-current hx:contrast-more:dark:border-current hx:border-blue-200 hx:bg-blue-100 hx:text-blue-900 hx:dark:border-blue-200/30 hx:dark:bg-blue-900/30 hx:dark:text-blue-200">
+  <p class="hx:flex hx:items-center hx:font-medium"><svg height=16px class="hx:inline-block hx:align-middle hx:mr-2" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor" aria-hidden="true"><path stroke-linecap="round" stroke-linejoin="round" d="M13 16h-1v-4h-1m1-4h.01M21 12a9 9 0 11-18 0 9 9 0 0118 0z"/></svg>Note</p>
+
+  <div class="hx:w-full hx:min-w-0 hx:leading-7">
+    <div class="hx:mt-6 hx:leading-7 hx:first:mt-0"><p>Notice we changed data type of <code>sum</code> to <code>long</code> in order to store 64 bit numbers.</p></div>
+  </div>
+</div>
+<p>Let&rsquo;s test some more</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-bash" data-lang="bash"><span style="display:flex;"><span>$ java SumLongOctal.java <span style="color:#e6db74">&#34;1777777777777777777776o&#34;</span>
+</span></span><span style="display:flex;"><span>Exception in thread <span style="color:#e6db74">&#34;main&#34;</span> java.lang.NumberFormatException: For input string: <span style="color:#e6db74">&#34;1777777777777777777776&#34;</span> under radix <span style="color:#ae81ff">8</span>
+</span></span><span style="display:flex;"><span>	at java.base/java.lang.NumberFormatException.forInputString<span style="color:#f92672">(</span>NumberFormatException.java:67<span style="color:#f92672">)</span>
+</span></span><span style="display:flex;"><span>	at java.base/java.lang.Long.parseLong<span style="color:#f92672">(</span>Long.java:709<span style="color:#f92672">)</span>
+</span></span><span style="display:flex;"><span>	at SumLongOctal.parseNumber<span style="color:#f92672">(</span>SumLongOctal.java:29<span style="color:#f92672">)</span>
+</span></span><span style="display:flex;"><span>	at SumLongOctal.main<span style="color:#f92672">(</span>SumLongOctal.java:18<span style="color:#f92672">)</span></span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>We can see that this number doesn&rsquo;t fit into <code>long</code> data type. So we need to use something called <a href="https://docs.oracle.com/javase/8/docs/api/java/math/BigInteger.html"target="_blank" rel="noopener"><code>BigInteger</code></a> and more specifically we will be using its <a href="https://docs.oracle.com/javase/8/docs/api/java/math/BigInteger.html#longValue--"target="_blank" rel="noopener"><code>BigInteger.longValue()</code></a> method.</p>
+<p>First we need to <em><strong>import</strong></em> it using</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#f92672">import</span> java.math.BigInteger;</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>and then we will replace</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#66d9ef">return</span> Long.<span style="color:#a6e22e">parseLong</span>(numberString.<span style="color:#a6e22e">substring</span>(0, numberStringLength <span style="color:#f92672">-</span> 1), 8);</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>with</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#66d9ef">return</span> <span style="color:#66d9ef">new</span> BigInteger(number.<span style="color:#a6e22e">substring</span>(0, numberStringLength <span style="color:#f92672">-</span> 1), 8).<span style="color:#a6e22e">longValue</span>();</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+<p>So the final code would be</p>
+<div class="hextra-code-block hx:relative hx:mt-6 hx:first:mt-0 hx:group/code">
+
+<div><div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-java" data-lang="java"><span style="display:flex;"><span><span style="color:#75715e">// SumLongOctal.java</span>
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span><span style="color:#f92672">import</span> java.math.BigInteger;
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span><span style="color:#66d9ef">public</span> <span style="color:#66d9ef">class</span> <span style="color:#a6e22e">SumLongOctal</span> {
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">public</span> <span style="color:#66d9ef">static</span> <span style="color:#66d9ef">void</span> <span style="color:#a6e22e">main</span>(String<span style="color:#f92672">[]</span> args) {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">long</span> sum <span style="color:#f92672">=</span> 0;
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">for</span> (String argument : args) {
+</span></span><span style="display:flex;"><span>            StringBuilder number <span style="color:#f92672">=</span> <span style="color:#66d9ef">new</span> StringBuilder();
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">for</span> (<span style="color:#66d9ef">char</span> c : argument.<span style="color:#a6e22e">toCharArray</span>()) {
+</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>Character.<span style="color:#a6e22e">isWhitespace</span>(c)) {
+</span></span><span style="display:flex;"><span>                    number.<span style="color:#a6e22e">append</span>(c);
+</span></span><span style="display:flex;"><span>                } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>                    sum <span style="color:#f92672">+=</span> parseNumber(number);
+</span></span><span style="display:flex;"><span>                    number <span style="color:#f92672">=</span> <span style="color:#66d9ef">new</span> StringBuilder();
+</span></span><span style="display:flex;"><span>                }
+</span></span><span style="display:flex;"><span>            }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>            sum <span style="color:#f92672">+=</span> parseNumber(number);
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>        System.<span style="color:#a6e22e">out</span>.<span style="color:#a6e22e">println</span>(sum);
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>
+</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">static</span> <span style="color:#66d9ef">long</span> <span style="color:#a6e22e">parseNumber</span>(StringBuilder number) {
+</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> (<span style="color:#f92672">!</span>number.<span style="color:#a6e22e">isEmpty</span>()) {
+</span></span><span style="display:flex;"><span>            String numberString <span style="color:#f92672">=</span> number.<span style="color:#a6e22e">toString</span>();
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">int</span> numberStringLength <span style="color:#f92672">=</span> numberString.<span style="color:#a6e22e">length</span>();
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">if</span> (numberString.<span style="color:#a6e22e">endsWith</span>(<span style="color:#e6db74">&#34;o&#34;</span>) <span style="color:#f92672">||</span> numberString.<span style="color:#a6e22e">endsWith</span>(<span style="color:#e6db74">&#34;O&#34;</span>)) {
+</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">return</span> <span style="color:#66d9ef">new</span> BigInteger(
+</span></span><span style="display:flex;"><span>                    number.<span style="color:#a6e22e">substring</span>(0, numberStringLength <span style="color:#f92672">-</span> 1),
+</span></span><span style="display:flex;"><span>                    8
+</span></span><span style="display:flex;"><span>                ).<span style="color:#a6e22e">longValue</span>();
+</span></span><span style="display:flex;"><span>            } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">return</span> Long.<span style="color:#a6e22e">parseLong</span>(numberString);
+</span></span><span style="display:flex;"><span>            }
+</span></span><span style="display:flex;"><span>        } <span style="color:#66d9ef">else</span> {
+</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">return</span> 0;
+</span></span><span style="display:flex;"><span>        }
+</span></span><span style="display:flex;"><span>    }
+</span></span><span style="display:flex;"><span>}</span></span></code></pre></div></div><div class="hextra-code-copy-btn-container hx:opacity-0 hx:transition hx:group-hover/code:opacity-100 hx:flex hx:gap-1 hx:absolute hx:m-[11px] hx:right-0 hx:top-0">
+  <button
+    class="hextra-code-copy-btn hx:group/copybtn hx:cursor-pointer hx:transition-all hx:active:opacity-50 hx:bg-primary-700/5 hx:border hx:border-black/5 hx:text-gray-600 hx:hover:text-gray-900 hx:rounded-md hx:p-1.5 hx:dark:bg-primary-300/10 hx:dark:border-white/10 hx:dark:text-gray-400 hx:dark:hover:text-gray-50"
+    title="Copy code"
+  >
+    <div class="hextra-copy-icon hx:group-[.copied]/copybtn:hidden hx:pointer-events-none hx:h-4 hx:w-4"></div>
+<div class="hextra-success-icon hx:hidden hx:group-[.copied]/copybtn:block hx:pointer-events-none hx:h-4 hx:w-4"></div>
+  </button>
+</div>
+</div>
+
+        </div>
+        <div class="hx:mt-16"></div>
+        <div class="hx:mt-16"></div>
+        
+      </main>
+    </article>
+  </div>
+
+      
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