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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 doesnt seem too complicated either.
Lets 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" />
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<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 doesnt seem too complicated either.
Lets 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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<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 doesnt seem too complicated either.
Lets 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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href="/courses/prog-intro/"
>Introduction to Programming in Java
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>Homeworks
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href="/courses/prog-intro/homeworks/fastreverse/"
>FastReverse
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href="/courses/prog-intro/homeworks/markup/"
>Markup
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href="/courses/prog-intro/homeworks/md2html/"
>Md2Html
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>Reverse
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href="/courses/prog-intro/homeworks/sum/"
>Sum
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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 "><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/sumbigdecimalhex/"
>SumBigDecimalHex
</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/sumbigintegeroctal/"
>SumBigIntegerOctal
</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/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/sumdoublehex/"
>SumDoubleHex
</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><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/conclusion/"
>Summing Up
</a>
</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/homeworks/wordstat/"
>WordStat
</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/wspp/"
>Wspp
</a>
</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/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 "><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/fastreverse/"
>FastReverse
</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/markup/"
>Markup
</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/md2html/"
>Md2Html
</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/reverse/"
>Reverse
</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/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/sumbigdecimalhex/"
>SumBigDecimalHex
</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/sumbigintegeroctal/"
>SumBigIntegerOctal
</a>
</li><li class="hx:flex hx:flex-col "><a
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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/prog-intro/homeworks/sum/sumdouble/"
>SumDouble
</a>
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href="/courses/prog-intro/homeworks/sum/sumdoublehex/"
>SumDoubleHex
</a>
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href="/courses/prog-intro/homeworks/sum/sumhex/"
>SumHex
</a>
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href="/courses/prog-intro/homeworks/sum/sumlongoctal/"
>SumLongOctal
</a>
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href="/courses/prog-intro/homeworks/sum/conclusion/"
>Summing Up
</a>
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href="/courses/prog-intro/homeworks/wordstat/"
>WordStat
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href="/courses/prog-intro/homeworks/wspp/"
>Wspp
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>Lectures
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>Lecture 1. Introduction
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<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">
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<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>
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</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
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-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>
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