Java Problem 21

The next problem I tried to solved was problem 21.

/*
 * 21. Write a Java class called Equals, which defines a 
 * main() method that asks the user to enter two Strings s1 
 * and s2, and displays whether or not s1 and s2 are equal. 
 * Two Strings are equal if they are of the same length 
 * and the same characters appear in the same positions. 
 * You MUST NOT use any of the methods defined in the String 
 * class other than charAt() and length().
 * 
 * @author obispo
 */

import javax.swing.*;
import java.text.*;
class Equals {
  public static void main( String[] args ) {
    String s1, s2;
    int result = 0, len, index;

    s1 = JOptionPane.showInputDialog(null, "Enter first string:");
    s2 = JOptionPane.showInputDialog(null, "Enter second string:");

    len = s1.length();
    if (len != s2.length()) {
      result = -1;  
    } else {
      for (index = 0; index < len; index++) {
        if (s1.charAt(index) != s2.charAt(index)) {
          result = -1;
        } 
      }   
    }
  
    if (result == 0) {
      JOptionPane.showMessageDialog(null, "Equal !\n" + 
                         s1 + " == " + s2); 
    } else {
      JOptionPane.showMessageDialog(null, "Not Equal !\n" + 
                         s1 + " != " + s2); 
    }
  }
}