Introduction to Classes, Objects, Methods and Strings - Java: How to Program Early Objects - page 71

Typically, the apps you develop in this topic will consist of two or more classes. If you
become part of a development team in industry, you might work on apps that contain
hundreds, or even thousands, of classes.

3.2 Instance Variables, set Methods and get Methods
In this section, you'll create two classes— Account (Fig. 3.1) and AccountTest (Fig. 3.2).
Class AccountTest is an application class in which the main method will create and use an
Account object to demonstrate class Account 's capabilities.

3.2.1 Account Class with an Instance Variable, a set Method and a get
Method
Different accounts typically have different names. For this reason, class Account (Fig. 3.1)
contains a name instance variable . A class's instance variables maintain data for each object
(that is, each instance) of the class. Later in the chapter we'll add an instance variable named
balance so we can keep track of how much money is in the account. Class Account con-
tains two methods—method setName stores a name in an Account object and method
getName obtains a name from an Account object.

1

// Fig. 3.1: Account.java

2 // Account class that contains a name instance variable

3 // and methods to set and get its value.

4
5 public class Account

6 {

7 private String name; // instance variable

8

9 // method to set the name in the object

public void setName(String name)
{
this .name = name; // store the name
}

10

11

12

13

14
15 // method to retrieve the name from the object

public String getName()
{
return name; // return value of name to caller
}

16

17

18

19

20 } // end class Account

Fig. 3.1 | Account class that contains a name instance variable and methods to set and get its
value.

Class Declaration
The class declaration begins in line 5:

public class Account

The keyword public (which Chapter 8 explains in detail) is an access modifier . For now,
we'll simply declare every class public . Each public class declaration must be stored in a file
having the same name as the class and ending with the .java filename extension; otherwise,