Java For Dummies, 7th Edition

Chapter 15

Fancy Reference Types

IN THIS CHAPTER

Writing and using a Java interface

Working with abstract classes

In previous chapters, you may have read about the things that full-time and part-time employees have in common. In particular, both the FullTimeEmployee and PartTimeEmployee classes can extend the Employee class. That's nice to know if you're running a small business, but what if you're not running a business? What if you're taking care of house pets?

This chapter explores the care of house pets and other burning issues.

Java’s Types

Chapter 4 explains that Java has these two kinds of types:

• Java has eight primitive types.

  The four that you use most often are int, double, boolean, and char.

• Java's API has thousands of reference types. And, when you write a Java program, you define new reference types.

  Java's String type is a reference type. So are Java's Scanner, JFrame, ArrayList, and File types. My DummiesFrame is a reference type. In Chapter 7, you create your own Employee, FullTimeEmployee, and PartTimeEmployee reference types. Your first You'll love Java! program has a main method inside of a class, and that class is a reference type. You may not realize it, but every array belongs to a reference type.

In Java, reference types are everywhere. But until ...