Writing Classes - Java Software Solutions: Foundations of Program Design - page 162

4.2 Anatomy of a Class
In all of our previous examples, we've written a single class containing a single
main method. These classes represent small but complete programs. These pro-
grams often instantiated objects using predefined classes from the Java class
library and used those objects for the services they provide. Those predefined
classes are part of the program too, but we never really concern ourselves with
them other than to know how to interact with them. We simply trust them to
provide the services they promise.
Let's look at another, similar example. The RollingDice class shown in
Listing 4.1 contains a main method that instantiates two Die objects (as in the
singular of dice). It then rolls the dice and prints the results. It also calls several
other methods provided by the Die class, such as the ability to explicitly set and
get the current face value of a die.
LISTING 4.1
//********************************************************************
// RollingDice.java Author: Lewis/Loftus
//
// Demonstrates the creation and use of a user-defined class.
//********************************************************************
public class RollingDice
{
//-----------------------------------------------------------------
// Creates two Die objects and rolls them several times.
//-----------------------------------------------------------------
public static void main (String[] args)
{
Die die1, die2;
int sum;
die1 = new Die();
die2 = new Die();
die1.roll();
die2.roll();
System.out.println ("Die One: " + die1 + ", Die Two: " + die2);
die1.roll();
die2.setFaceValue(4);