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From: markspace <-@.>
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Subject: Re: equals(), Sets, Maps, and degrees of equality
Date: Thu, 10 Nov 2011 19:07:24 -0800
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On 11/10/2011 5:58 PM, Eric Sosman wrote:

>  markspace's idea of endowing each Dog
> with a DogComparisonStrategy wouldn't work if the same Dog instance
> could be a member of the Set *and* a key in the Map:


Right.  It's really not that different than making subclasses to handle 
different schemes.  It just tries to be a bit more pithy about how it 
does it.  I'm mostly just tossing it out there to spur a little thought 
and discussion.  The "concurrency" comment caught me off guard, I'll admit.

I actually like the suggestion to use a Tree with a supplied Comparator. 
  It seems closest to what the OP really needs.  Second choice is just 
use the wrappers.  Third choice: if profiling shows wrappers or the Tree 
slowing things down, implement custom Map/Set classes to do exactly 
what's needed.


> You'd need to
> visit every Dog and reset its DogComparisonStrategy before doing


Stuff like that probably isn't kosher.  What if some external process 
affects the the Map or Set right in the middle of iterating over its 
contents?  This could be really ugly and a real maintenance hazard.