Memory usage information of a Java Program [duplicate]

This question already has answers here: Closed 11 years ago.

Possible Duplicate:

How to monitor Java memory usage?

My Java Program loads hash map with large number of values from the database. Is there any way through which I may know that how much memory each of my hash map is using during the program i开发者_Go百科s running.

I am aware that it may not be a constant value but any near approximation will also do. Or maybe how much memory each of the hash map consumes while it is loaded with data from Sql Server.

Thanks

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If you want to estimate the size of specific data structures at runtime, Heinz Kabutz's newsletter describes how to do this using instrumentation: Instrumentation Memory Counter.

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If you want an estimate use a profiler like VisualVM or YourKit.

You could estimate how large an entry key/value is and multiply it by the number of entries.