visual vm analyze memory leak

in my visual vm, i click on sample->memory, and i keep see "windowprincipal" class, instances stay at 25. even that right now nobody using the application. is this sign of memory leak?

http://www.freeimagehosting.net/image.php?c069df开发者_运维百科48c2.gif

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Trying requesting a Garbage Collection multiple times and then see this graph again. If the object instances are still there than you can trace the patch of these objects i.e., who is referencing these objects and from that you can assess if this is a memory leak or just legitimate objects which are cached.