JConsole is a built-in Java performance profiler that works from the command-line and in a GUI shell. It's not perfect, but it's an adequate first line of defense
The most effective response to a performance problem is to use a profiler rather than reviewing the code or JVM garbage collector flags.
Monitor the class count - if the count steadily rises, then you can assume that either the app server or your code has a ClassLoader leak somewhere and will run out of PermGen space before long.
com.sun.management.HotSpotDiagnostic has a "dumpHeap" mebean operation that allows a dump to be created (remotely) which can be analysed later.
jstat can monitor garbage collection and JIT compiler statistics
- jstack will get a stack dump from any process
jmap can produce a dump of the heap, or a histogram of live classes and how many instances there are and the spaced used by them.
jhat supports analysing heap dumps obtained from jmap or jconsole or HotSpotDiagnostic.dumpHeap
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