update

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

@@ -1,17 +1,32 @@
 // Sum.java
 
 public class Sum {
+
     public static void main(String[] args) {
-        System.out.println("number of arguments: " + args.length);
-        
         int sum = 0;
         for (String argument : args) {
-            sum = sum + argument;
-            System.out.println(argument);
-            System.out.println(sum);
+            StringBuilder number = new StringBuilder(); // we will form numbers here using StringBuilder
+            for (char c : argument.toCharArray()) {
+                if (!Character.isWhitespace(c)) {
+                    // if character is not whitespace
+                    number.append(c); // concatenate new digit
+                } else {
+                    // if character is whitespace
+                    if (!number.isEmpty()) {
+                        // if number is not empty
+                        sum = sum + Integer.parseInt(number.toString()); // add number to sum
+                    }
+                    number = new StringBuilder(); // empty the number by creating new empty StringBuilder
+                }
+            }
+
+            // check for any remaining digits in number
+            if (!number.isEmpty()) {
+                // if number is not empty
+                sum = sum + Integer.parseInt(number.toString()); // add number to sum
+            }
         }
-        
+
         System.out.println(sum);
     }
 }
-