Question

Maybe I am just crazy, or maybe I forgot the way things should work. But I was chasing down a bug (while learning some Groovy) and found that the following assertion fails. I guess I thought that when using a string literal, a new instance of String would be created for it. Am I wrong?

String one = 'one'
String two = 'one'

// I thought this should fail, but it doesn't
assert one.is(two) == false

one = new String("one")
two = new String("one")

// This works as expected
assert one.is(two) == false

By using the dump() method, I can see that they are indeed the same instance of String. Any help or guidance would be appreciated.

Thanks!

Answer 1

When you use String literals, Java allows them to be interned, so you get the same instance..

The section 2.3 in the VM spec mentions this.

String literals and, more generally, strings that are the values of constant expressions are “interned” so as to share unique instances, using the method String.intern.

Groovy also follows this rule