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You will need to move all the code out of the main() method.

The way the class is now coded, there is no sense in having another class to test it.

Why?
If the code does all it's supposed to as it is now, what would a Demo do?

The code has one method: main(). There is not any meaningful way to have another class go with it.

what happens when you compile the class? Any errors?
What happens when you execute the class? Any errors?
Does it do what you want?

The class has a main() method and shouldn't need another...