Tower's of Hanoi using Stacks - Java

-snip-

That gives me:

Code:

Exception in thread "main" java.lang.NullPointerException
    at Tower.addDisc(Tower.java:11)
    at TOHModel.<init>(TOHModel.java:10)
    at TOHFrame.<init>(TOHFrame.java:7)
    at TOHApp.main(TOHApp.java:5)
Java Result: 1

Which indicates there is a problem with Tower.
I wish I learned objects more in depth.

s is null according to the debugger, but I thought having

Code:

private Stack s;
    
    public void Tower(){
        s = new ArrayListStack();
    }

initialized it?

EDIT:
GOT IT.
I had public void Tower(), should be public Tower().
Derp mistake.

I WILL BE UPDATING THIS THREAD WITH MORE PROBLEMS, THOUGH. Thanks guys!

now to figure out how to paint the discs