public class MyPair
{
   /* Calls MyString.equals(MyString) because we know thing2 is of type MyString. */
   public void diagonal(MyString thing1, MyString thing2)
   {
      System.out.println(thing1 + " and " + thing2 + " are equal: " + thing1.equals(thing2));
   }

   public static void main(String[] args)
   {
      MyPair pair = new MyPair();
      pair.diagonal(new MyString("a"), new MyString("b")); // false
      pair.diagonal(new MyString("c"), new MyString("c")); // true
   }
}