Question

I have an abstract java class that implements a couple of its methods, but not others. In the methods it implements it uses a private attribute variable. The variable used also needs to be used in a subclass.

As I see it my options are:

• Declare the private variable in both the subclass and the super class
• defer the implementation of the methods currently implemented in the abstract class to the subclasses

Are there other options? Which of these makes more sense and why?

Answer 1

The question is how you want to maintain your state: If it is of no concern, where the value is stored, you can just add a private member “on top” of the other and use that instead of the one in the superclass. If you want to have some methods from your superclass and some methods from your subclass to access the same state, you need to change visibility:

You could declare the variable as protected, making it accessible in the subclass, or implement accessor methods, or even make it public.