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Groups > comp.lang.java.programmer > #6301

HashSet keeps all nonidentical equal objects in memory

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Hi,

I've been doing java programming for over 10 years, but now I've
encoutered a phenomenon that I wasn't aware of at all.
I had an application in which I have a HashSet<String>. I added a lot
of different String objects to this HashSet, but many of the String
objects are equal to each other. Now, after a while my application ran
out of memory, even with -Xmx1500M. This happened when there were only
about 7000 different Strings in the set! I didn't understand this,
until I started adding the "intern()" of every String object to the
set instead of the original String object. Now the program needs
virtually no memory anymore.
There is only one explanation: before I used "intern()", ALL the
different String objects, even the ones that are equal, were kept in
memory by the HashSet! No matter how strange it sounds. I was
wondering, does anybody have an explanation as to why this is the case?

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HashSet keeps all nonidentical equal objects in memory Frederik <landcglobal@gmail.com> - 2011-07-20 02:43 -0700
  Re: HashSet keeps all nonidentical equal objects in memory Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-07-20 07:30 -0400
  Re: HashSet keeps all nonidentical equal objects in memory Frederik <landcglobal@gmail.com> - 2011-07-20 04:09 -0700
    Re: HashSet keeps all nonidentical equal objects in memory markspace <-@.> - 2011-07-20 08:22 -0700
  Re: HashSet keeps all nonidentical equal objects in memory Robert Klemme <shortcutter@googlemail.com> - 2011-07-20 08:38 -0700
    Re: HashSet keeps all nonidentical equal objects in memory lewbloch <lewbloch@gmail.com> - 2011-07-20 09:31 -0700

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