Java How To Program, Late Objects, 11th Edition

... without duplicating code? Next we answer this question, using a more elegant approach to building classes that emphasizes the benefits of inheritance.

Software Engineering Observation 9.3

With inheritance, the instance variables and methods that are the same for all the classes in the hierarchy are declared in a superclass. Changes made to these common features in the superclass are inherited by the subclass. Without inheritance, changes would need to be made to all the source-code files that contain a copy of the code in question.

9.4.3 Creating a CommissionEmployee–BasePlusCommissionEmployee Inheritance Hierarchy

Now we declare class BasePlusCommissionEmployee ...