java main arg[] behaviour

[Lucas Toledo]

I have the following program

public class ArgIt {
        public static void main(String[] args){
                if(args[0].equals("x")) System.out.print("x3");
                if(args[0] == "x") System.out.println("x2 ");
                if ("x"=="x") System.out.println("x3 ");
        }
}

when I run it
java ArgIt x
it does not print x2.
Why is that? why is it that when the string passed as an argument to the program is not ==??? does the args have a different value?
why is then "x"=="x" when args[0] is not equal (==) to "x" ?

thanks in advance,
Lucas

[Matthew Brown]

Basically, you should never use == to compare Strings. You should always use equals(). However, because of the way the String pool is managed, == will sometimes give the right results. Line 5 is an example - using String literals will result in the same object being used, so == does what you expect. But this behaviour should never be relied on, and line 4 shows an example why.

[John Jai]

A good read - ScjpTipLine-StringsLiterally