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From Glen Mazza <grm7...@yahoo.com>
Subject Re: String.intern() thoughts
Date Mon, 01 Dec 2003 22:16:06 GMT
--- "J.Pietschmann" <j3322ptm@yahoo.de> wrote:
> Glen Mazza wrote:
> > No need-the "gotcha" site you gave earlier did
> give
> > some specific drawbacks under string compares:  
> > 
> > http://mindprod.com/jgloss/gotchas.html#COMPARISON
> 
> That's not a drawback. Interned strings allow
> comparision of
> references:
>    String a="a".intern();
>    String b="a".intern();
>    if(a==b) { System.out.println("equal"); }
> With non-interned strings you need a.equals(b),
> which
> may be slower, for longer strings anyway.
> 
> The most important gotcha is that interned strings
> may lock
> up memory forever. 

Yes, I may have misread that--outside of the fact that
strings are not GC'ed away, the intern() function does
not look that bad (their mention of a possible 64K
limit may be an issue if we also keep property values,
however.)  Still, I still don't know enough at this
stage to rule out any particular design.

> If interning is done only for
> property
> names and enumeration tokens (in contrast to
> property values),
> this may be acceptable.
> 

If we just do that, I believe we're back to
enumeration tokens, which don't need intern() anyway.

I think the next thing to consider is the storage of
specified vs. computed values.  Let's say we store
pointers for many properties to the same
{"property-name", "property-value"} pair.  A specified
property value of "10%" would not make this a very
helpful data structure if that percentage resolves to
different computed values for each property sharing
this pair.  I believe the goal for us then would be
just store the computed value for each pair (meaning
many more pairs), as long as we take into account the
can't-resolve-everything-without-knowledge-of-layout
issue.

Glen


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