A Rectangle Class
Example 2-1 shows a
class that represents a rectangle. Each instance of this Rect
class has four fields, x1
, y1
,
x2
, and y2
, that define the coordinates of the
corners of the rectangle. The Rect
class also defines a number of methods that operate on those
coordinates.
Note the toString( )
method. This method overrides the toString(
)
method of java.lang.Object
, which is the implicit
superclass of the Rect
class.
toString( )
produces a String
that represents a Rect
object. As you’ll see, this method is
quite useful for printing out Rect
values.
Example 2-1. Rect.java
package je3.classes; /** * This class represents a rectangle. Its fields represent the coordinates * of the corners of the rectangle. Its methods define operations that can * be performed on Rect objects. **/ public class Rect { // These are the data fields of the class public int x1, y1, x2, y2; /** * The is the main constructor for the class. It simply uses its arguments * to initialize each of the fields of the new object. Note that it has * the same name as the class, and that it has no return value declared in * its signature. **/ public Rect(int x1, int y1, int x2, int y2) { this.x1 = x1; this.y1 = y1; this.x2 = x2; this.y2 = y2; } /** * This is another constructor. It defines itself in terms of the above **/ public Rect(int width, int height) { this(0, 0, width, height); } /** This is yet another constructor. */ public Rect( ) { this(0, 0, 0, 0); } /** Move the rectangle by the specified amounts ...
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