how to detect a thread deadlock in netbeans

I believe that I have a deadlocking problem with a bunch of threads in a java netbeans app. When the app works, it works very well, scaling with the number of processors. When it doesn't, data is corrupted or the app itself locks entirely, as would be expected when threading goes bad.

I need to debug into the threads that he's implemented to find 开发者_JS百科out what the threads are doing when the app freezes. How can I do this in Netbeans? I press the 'pause' button, but no stack traces or thread traces are showing up. I can put breakpoints prior to the (alleged) deadlock, but that approach appears to bypass the lock problem altogether. I want to be able to unravel the situation as it arises.