Restricting 2 java instance running on the same machine

Hi, I need to restrict 2 instance of the same program on a single machine. how to acheive this. eg) consider a helloworld java programm run from 2 different command prompt

i need to bring the first instance on top when ever the user tries to run another instance from the same machine

any suggestions is greatly appreciated

Regards

Bala

[367 byte] By [balabaska] at [2007-9-27 9:56:24]