Understanding interfaces and abstract classes and methods in Java. This Java code challenge demonstrates many important concepts about interfaces, abstract methods, and more.

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 ...

Abstract classes can have abstract and regular methods. Abstract methods have a signature with no implementation body. Abstract methods can only be used in abstract classes and are used to specify ...

A public method should never be called by another public method within the same class hierarchy. It should only be called by other classes via the classes' public interface. Class calls might not be ...