Thread Button in servlet

Hi All,
I want to have a servlet or jsp page which has several buttons named 'Start'.
On clicking a 'Start' button, it should generate a thread (in another class) and run a process and the button will become 'stop'.
On clicking the stop button, the thread should stop. I can click any button at any time and start the thread and stop in at any time.
Can anyone tell me any technique for this problem?
Regards,
Pradhip

i can't find why a nullPointerException occurs if i don,t see the code!

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              >
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