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.
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 ...