Writing Classes - Java Software Solutions: Foundations of Program Design - page 164

int size, weight;
char category;
double value, cost;

Data
declarations

Method
declarations

FIGURE 4.2 The members of a class: data and method declarations

The Die class is shown in Listing 4.2. It contains two data values: an integer
constant ( MAX ) that represents the maximum face value of the die, and an inte-
ger variable ( faceValue ) that represents the current face value of the die. It also
contains a constructor called Die and four regular methods: roll , setFaceValue ,
getFaceValue , and toString.
You will recall from Chapters 2 and 3 that constructors are special methods
that have the same name as the class. The Die constructor gets called when the
new operator is used to create a new instance of the Die class. The rest of the
methods in the Die class define the various services provided by Die objects.
We use a header block of documentation to explain the purpose of each
method in the class. This practice is not only crucial for anyone trying to under-
stand the software, it also separates the code visually so that it's easy for the eye
to jump from one method to the next while reading the code.
Figure 4.3 lists the methods of the Die class. From this point of view, it looks
no different from any other class that we've used in previous examples. The only
important difference is that the Die class was not provided for us by the Java
standard class library. We wrote it ourselves.
The methods of the Die class include the ability to roll the die, producing a
new random face value. The roll method returns the new face value to the call-
ing method, but you can also get the current face value at any time using the
getFaceValue method. The setFaceValue method sets the face value explicitly,
as if you had reached over and turned the die to whatever face you wanted. The
toString method of any object gets called automatically whenever you pass the
object to a print or println method to obtain a string description of the object

VideoNote

Dissecting the Die
class.