Question

I want to demonstrate with a few line of code that in Java, that to compare two strings (String), you have to use equals() instead of the operator ==.

Here is something I tried :

public static void main(String Args[]) {
   String s1 = "Hello";
   String s2 = "Hello";

   if (s1 == s2)
      System.out.println("same strings");
   else
      System.out.println("different strings");
}

I was expecting this output : different strings, because with the test s1 == s2 I’m actually comparing two references (i.e. addresses) instead of the objet’s content.

But I actually got this output : same strings !

Browsing the internet I found that some Java implementation will optimize the above code so that s1and s2 will actually reference the same string.

Well, how can I demonstrate the problem using the == operator when comparing Strings (or Objects) in Java ?

Answer 1

The compiler does some optimizations in your case so that s1 and s2 are really the same object. You can work around that by using

String s1 = new String( "Hello" );
String s2 = new String( "Hello" );

Then you have two distinct objects with the same text content.