The default JPDA options are as follows:
-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n
If you substitute suspend=y, the JVM starts in suspended mode and stays suspended until a debugger attaches to it. This is helpful if you want to start debugging as soon as the JVM starts.
To specify the port to use when attaching the JVM to a debugger, specify address=port_number.
You can include additional options. A list of JPDA debugging options is available here:
http://java.sun.com/products/jpda/doc/conninv.html#Invocation