What is String.intern ?

[Garrett Smith]

intern()
Returns a canonical representation for the string object.
I've never used it and I don't know what a canonical representation is. What is it what's it used for?

[Ron Newman]

The idea behind intern() is that there is one and only one interned string with a particular value. So if you intern a bunch of strings, you can later compare them using
== rather than equals().
The API documentation explains this more clearly.
[ October 13, 2002: Message edited by: Ron Newman ]

[Garrett Smith]

Oh, I see now. All String literals are interned. That's why String literals are == but Strings constructed w/new String are !=
Better explained in code:

public class intern {
    public static void main(String[] s){
    
        String a = "chocolate";
        String b = "chocolate";
        
        String c =  new String(new char[]{'c','h','o','c','o','l','a','t','e'});
    
        System.out.println("a == b  = " + a == b);
        System.out.println("a == c  = " + a == c);
        System.out.println("c.intern() = " + c.intern());
        System.out.println("(a == c.intern()) = " + (a == c.intern()));
    }
}

Running:

localhost# java intern      
a == b  = true
a == c  = false
c.intern() = chocolate
(a == c.intern()) = true

[Dirk Schreckmann]

Looks like you're understanding the concept well.
You may want to take a look at Roedy Green's Java Glossary on interned Strings for a detailed explanation as well as a gotcha to be aware of.