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At line 307 in the actionPerformed method, your code called parseInt with a null argument which the JVM did not like and so thru this exception. You need either catch the exception and handle it or...

If you don't see any output, then the System.out.print("hi frm method": + YOURMETHODNAMEHERE) statement is NOT being executed. That should tell you something about how and where your program is...

I don't see any debugging print outs in your code.

Have you tried debugging the code by adding print outs of the variables as they change and to show logic flow?

Start by adding print out first...