Object-Oriented Programming: Inheritance

Say not you know another entirely, till you have divided an inheritance with him.

Johann Kasper Lavater

This method is to define as the number of a class the class of all classes similar to the given class.

Bertrand Russell

Good as it is to inherit a library, it is better to collect one.

Augustine Birrell

Save base authority from others' books.

William Shakespeare

OBJECTIVES

In this chapter you will learn:

  • How inheritance promotes software reusability.
  • The notions of superclasses and subclasses.
  • To use keyword extends to create a class that inherits attributes and behaviors from another class.
  • To use access modifier protected to give subclass methods access to superclass members.
  • To access superclass members with super.
  • How constructors are used in inheritance hierarchies.
  • The methods of class Object, the direct or indirect superclass of all classes in Java.

Outline

Introduction

Superclasses and Subclasses

protected Members

Relationship between Superclasses and Subclasses

Creating and Using a CommissionEmployee Class

Creating a BasePlusCommissionEmployee Class without Using Inheritance

Creating a CommissionEmployeeBasePlusCommissionEmployee Inheritance Hierarchy

CommissionEmployeeBasePlusCommissionEmployee Inheritance Hierarchy Using protected Instance Variables

CommissionEmployeeBasePlusCommissionEmployee Inheritance Hierarchy Using private Instance Variables

Constructors in Subclasses

Software Engineering with Inheritance

Object Class

(Optional) GUI and Graphics Case Study: Displaying Text and Images Using Labels

Wrap-Up