Chapter 5

Defining Classes


  • What a class is, and how you define a class
  • How to implement class constructors
  • How to define class methods
  • What method overloading is
  • What a recursive method is and how it works
  • How to create objects of a class type
  • What packages are and how you can create and use them
  • What access attributes are and how you should use them in your class definitions
  • What nested classes are and how you use them

In this chapter you explore the heart of the Java language: classes. Classes specify the objects you use in object-oriented programming. These form the basic building blocks of any Java program, as you saw in Chapter 1. Every program in Java involves classes because the code for a program can appear only within a class definition.

You explore the details of how a class definition is put together, how to create your own classes, and how to use classes to solve your own computing problems. And in the next chapter, you build on this to look at how object-oriented programming helps you work with sets of related classes.


As you saw in Chapter 1, a class is a prescription for a particular kind of object — it defines a new type. You use the definition of a class to create objects of that class type — that is, to create objects that incorporate all the components specified as belonging to that class.


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