You appear never to have posted code, so you don't know about the
code tags, which I added to your code, and doesn't it look better
Always use the code tags.
I would have sorted out the
lines that are too long or the excess empty lines, but left them unchanged so as to maintain your line numbers. The long lines are caused by your using the automatic GUI builder on your
IDE.
Please supply the full stack trace which will allow you to work out why you are suffering that exception. The cure for null pointer exceptions is to replace the null by something “real”.
I can see at least three other errors.
Why have you got static fields at the end of the second code block?
Why are you creating a percentage by dividing 100? You will almost certainly get the wrong result because of the conventions of integer arithmetic.
Why are you using Thread#sleep? Which thread is that sleep call on?
The correct Java® style is for all class names to start with CapitalLetters.
It is usually bad design to extend GUI classes.