Java: find common characters in two strings
<p>I'm asked to write a program that finds the common characters in two strings using the <strong>indexOf(char)</strong> method and a <strong>for loop</strong>. Here's what I have so far - the output comes out blank still.</p>

<pre><code>import java.util.Scanner;
public class ClassName {
   public static void main (String args []) {

   Scanner input = new Scanner (System.in);

   String a = "";
   String b = "";
   String c = "";

   System.out.print("Enter two words: ")
   a = input.nextLine();
   b = input.nextLine();

   for (int i = 0; i &lt; a; i++){

      char ch = a.charAt(i);
      if (b.indexOf(ch) != -1){
         c = c+String.valueOf(ch);
         }
      }
System.out.print("Common letters are: "+c);
}
</code></pre>

<p>}</p>

<p><a href="https://i.stack.imgur.com/gNGXz.png" rel="nofollow noreferrer">output here</a></p>

<p>I'm not sure where to go from here.</p>

<p>thanks</p>