Inheritance

Inheritance is fundamental to object-oriented programming. It allows us to create new classes that reuse, extend, and/or modify the behavior of the preexisting ones. The preexisting class is called the super (or base or parent) class, and the brand new class we are creating is called the derived class. There is a restriction on how many super classes we can inherit from; on a JVM, you can only have one base class. But you can inherit from multiple interfaces. Inheritance is transitive. If class C is derived from class B and that class B is derived from a given class A, then class C is a derived class of A.

A derived class will implicitly get all the parent classes (and the parent's parent class, if that is the case) fields, properties, and methods. The importance of inheritance lies in the ability to reuse code that has already been written and therefore avoid the scenario where we would have to reimplement the behavior exposed by the parent class. A derived class can...