Now that I look at your code, it looks like you're mixing ItemListener and ActionListener. You have a method, itemStateChanged(ActionEvent event). It looks like that's the method you intended to name actionPerformed.
If you implement the interface, ItemListener, then you override the method, itemStateChanged(ItemEvent e).
If you implement the interface, ActionListener, then you override the method, actionPerformed(ActionEvent e).
"We're kind of on the level of crossword puzzle writers... And no one ever goes to them and gives them an award." ~Joe Strummer sscce.org
Try adding @Override (called an annotation) immediately before the method as in the following code. Doing so will give you an error when you think you are overriding a method but actually are not because you have not specified the interface on your implements line or have the method signature wrong.