Description of a Class

In a mathematics book, "point" is given a precise mathematical definition. For programming, a precise software description of class Point is needed. The Java class libraries come with descriptions of the classes within them. The documentation for Point is found in the Java documentation under the section for the AWT. There you will see something like the following:

public  class  java.awt.Point   

// Fields
int x; 
int y; 

// Constructors
Point();                 // creates a point at (0,0)
Point(int  x, int  y);   // creates a point at (x,y)
Point( Point pt );       // creates a point at the location given in pt

// Methods
boolean equals(Object  obj);  // checks if two point objects hold equivalent data
void move(int  x, int  y);    // changes the (x,y) data of a point object 
String toString();            // returns character data that can be printed

(I've left out some methods we won't be using.)

The documentation shows the data that an object of that class contains (its variables), the methods that are used to manipulate that data, and the constructors that are used to create objects of the class. Sometimes (as here) the variables called fields. The two variables are named x and y and are of type int.