String == String

[AndrewM16921]

This is weird.

So, I was teaching somebody how to use Java and I had essentially said if you compare two strings with == they are not necessarily equal even if they have the same value. So...

String str1 = "text";
String str2 = "text";

System.out.println(str1 == str2);

This printed out true.

...WHAT? Does == now evaluate based on .equals rather than the reference or something? Or am I missing something here...

[2by4]

The compiler knows that a constant cannot change. So it creates only on copy of "text" in memory.

Try this..

String str1 = "text";
String str2 = new String("text");

This also..

String str1 = "text";
String str2 = str1 + "";

System.out.println(str1 == str2);

I guess it all depends on how clever the compiler is.

[pbrockway2]

if you compare two strings with == they are not necessarily equal even if they have the same value

That's right, if you mean by "have the same value" that they are made up of the same characters in the same order.

Your example is not inconsistent with that. Two strings made up of ... (equals() for short) may or may not be ==. If you want an example that prints false, try

String str1 = new String("text");
String str2 = new String("text");

In the example you tried the strings were interned.

[AndrewM16921]

Ah, I get it. I don't like it, but I get it. =P

Thanks.