title: string multiplication
body: <p>I am trying to multiply two strings, but I am getting the wrong answer. Any help will be appreciated:</p>
  
  <pre><code>public class stringmultiplication {
      public static void main(String[] args) {
          String s1 = "10";
          String s2 = "20";
          int num = 0;
          for(int i = (s1.toCharArray().length); i &gt; 0; i--)
              for(int j = (s2.toCharArray().length); j &gt; 0; j--)
                  num = (num * 10) + ((s1.toCharArray()[i - 1] - '0') * (s2.toCharArray()[j - 1] - '0'));
          System.out.println(num);
      }
  }
  </code></pre>