ps-aef | grep string gives [1]+ Done but when i check again it does not show any process running for it.

the ps command behave differently depends on your OS implemetation, but it should not kill any of the process, the process could complete when you type in the ps command.
If your system has the BSD style ps, you can use:
ps -uax | grep JPiTest
otherwise, you can use
ps -ef | grep JPiTest
man ps
in your box to find out the exact usage of the ps command for your version of OS.