Use Sysinternal's Process Explorer. Like task manager, this application can show you all running processes.
But it can also show you the command line arguments used to launch the process: right click the column headers and select the "command line" column. This extra information will help you identify which java application is running in a given
If that is not yet enough information, Process Explorer can also tell you which files, network connections, registry entries etc. are being used by the process.
update: as mentioned in the comments below, the standard Windows Task Manager can also show the command line. Go to "View" - "Select Columns..." and check "Command Line".