How to test java application for performance bottlenecks?

I am reviewing a big java application to see if there are any performance bottlenecks. The real problem is that I cannot pinpoint the performance issues to any single module. The whole application is slow as such.

Is there some tool/technique I can use to help me out in this?

From stackoverflow Niyaz

• Try using a profiler on your running code. It should help you identify the bottlenecks. Try jprofiler or Netbeans profiler

  From bibix

• If you are running on Java 6 you can use the supplied monitoring tools

  From HadleyHope

• You could have a look at this post too: http://stackoverflow.com/questions/12927/if-you-have-a-java-application-that-is-consuming-cpu-when-it-isnt-doing-anythin

  e5 : Please update link to: http://stackoverflow.com/questions/12927/if-you-have-a-java-application-that-is-consuming-cpu-when-it-isnt-doing-anythin
  From svrist

• For testing/development purposes, you can download Oracle JRockit Mission Control for free from this site. (Requires Login, but accounts can be set up with any email adress)

  Docs Here. It will allow you to find hotspots, memory leaks and much more.

  From Tnilsson

• I'm often happy enough using Java -Xprof. This gives you a sorted list of the functions your code spends most of its time in.

  From wvdschel