Abstract classes and interfaces in Java serve fundamentally different purposes. Learn the differences between these Java language elements and how to use them in your programs.

For example, refactoring the Car class may also require changing ProduceCar and AssembleCar. Moreover, if the changes are factory specific, then you may need to change other classes as well.

An abstract class can declare fields, constructors, and non-abstract methods in addition to or instead of abstract methods. For example, an abstract Vehicle class might declare fields describing ...