Rather than using a third party tool, you can also make a pretty good guess by looking at all the columns in task manager if you know roughly what the various java processes on your system are. From the Processes tab, use View-> Select Columns and add PID, CPU Time, VM Size, and Thread count. Knowing roughly what the process is doing should help narrow it down.
For example, in a client-server app, the server will likely use more memory, have more threads, and have used more CPU time because it has been running longer. If you're killing a process because it's stuck, it might simply be using more CPU right now.
MAX java heap memory is usually directly reflected in VM Size. So if you're using -Xmx flags, the process with the larger setting will have a larger VM Size.