When you get this sort of problem it's best to read the API docs for the class to see what type the method actually returns. The docs say the getItemSelectable() method returns an object of type ItemSelectable (which in your case is the JCheckbox) but you are trying to cast it to a type Choice, which it isn't.
I’ve looked at a lot of different solutions, and in my humble opinion Aspose is the way to go. Here’s the link: http://aspose.com
subject: ItemListener: Exception in thread "AWT-EventQueue-1"