String interning (WAS: SAX2/Java: Towards a final form)

[Miles Sabin]

David Brownell wrote,
> Miles Sabin wrote,
> > Except that String.intern() isn't the _only_ way of 
> > making foo.equals(bar) iff foo == bar (in particular 
> > contexts, as opposed to across the whole JVM).
>
> It's the only way to ensure it's so if foo is a string 
> literal, as is rather common usage.

I don't follow. You're surely not suggesting that

  foo == "literal".intern()

is faster than,

  foo.equals("literal")

are you?

I assume not, but then I don't really see your point. It'd be
easy enough to pre-populate an app-intern map with all the 
literals you were interested in. Granted, getting any benefits 
from this in a ContentHandler (as opposed to in a parser 
implementation) would mean we'd need something akin to Lars 
StringInterner interface to do the pre-populating.

Anyhow, maybe the waters are getting a bit muddied. I'm
assuming that all parsers will do interning of one sort or
another internally. The issue for me is how much of that gets
exposed via the SAX API. I don't want java-interning exposed,
because that means my parser has no option but to use
String.intern().

OTOH, _if_ the consensus is that some sort of interning must be 
exposed for the convenience of ContentHandler implementors then 
I'll go along with it, just so long as it's specified in such a 
way that it can be implemented in a completely thread-local 
way.

But I'd much prefer it if the SAX API didn't expose any
interning behaviour at all. I think we agree on that?

Cheers,


Miles

-- 
Miles Sabin                       Cromwell Media
Internet Systems Architect        5/6 Glenthorne Mews
+44 (0)20 8817 4030               London, W6 0LJ, England
msabin at cromwellmedia.com          http://www.cromwellmedia.com/


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