Sams Teach Yourself Object Oriented Programming in 21 Days, Second Edition

Chapter 5. Inheritance: Time to Write Some Code

Inheritance is a powerful tool. Today you will explore the use of this new tool through a number of hands-on lab exercises. By the end of today’s lesson, you should feel a bit more comfortable with the theory presented on Day 4.

Today you will learn

• How to use inheritance while programming

• How abstract classes help you plan inheritance

• About the importance of the “Is-A” and “Has-A”

• How Java may have violated the “Is-A” and “Has-A” relationship

Lab 1: Simple Inheritance

Listing 5.1 presents the personified MoodyObject baseclass.

Example 5.1. MoodyObject.java

public class MoodyObject { // return the mood protected String getMood() { return "moody"; } // ask the object how it feels public void queryMood() { ...