Sams Teach Yourself Java™ in 24 Hours, Sixth Edition

Putting One Class Inside Another

Although a Java program is called a class, there are many occasions when a program requires more than one class to get its work done. These programs consist of a main class and any helper classes that are needed.

When you divide a program into multiple classes, there are two ways to define the helper classes. One way is to define each class separately, as in the following example:

public class Wrecker {    String author = "Ignoto";    public void infectFile() {        VirusCode vic = new VirusCode(1024);    }}class VirusCode {    int vSize;    VirusCode(int size) {        vSize = size;    }}

Caution

If more than one class is defined in the same source file, only one of the classes can be public. The other classes ...