RE: Cost of instantiating

Because it would require performing a lookup for every new object to see
if it matched one already created, and adding that lookup under the
covers to the constructor.

The intern() method on String does just that, but AFAIK is only called
for String literals, since that's done during startup and the overhead
is deemed worth it.  Adding that lookup for every newly created String
object would probably be way too much overhead.

The cool thing is that you can call String.intern() yourself on any
String variables you create, and then you can compare them using ==
instead of equals().  And of course nothing is stopping you from
creating your own version of intern() for any other object types.

Joe


> From: Paul Morgan
> 
> I'm getting immutables confused with string constants:
> 
>         String s1 = "XYZ";
>         String s2 = "XYZ";
> 
>         System.out.println(s1 == s2);
> 
> prints true.
> 
> Not the same thing though.
> 
> Sorry,
> Paul (wondering why this wouldn't work for immutables)