Cloneable and Immutable

[David Holmes - Sun Microsystems]

Florian Weimer said the following on 08/20/09 17:24:
> * Max Wang:
> 
>> Also, if it's a final class, is it better to simply return this?
> 
> No, in this case, it's better not to implement clone() at all.  One
> thing that's pretty clear in the Object#clone() contract is that it's
> a fresh object, that is, that x.clone() != x.  Even with immutable
> objects, the difference is observable with synchronization and
> identity-based hashing.

That's only a recommendation not a hard contract:

"The general intent is that, for any object x, the expression:

      x.clone() != x

will be true, and that the expression:

      x.clone().getClass() == x.getClass()

will be true, but these are not absolute requirements. "

One has to wonder why it was specified this loosely ...

David Holmes