Java Reference
In-Depth Information
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 com.davidflanagan.examples.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 */
public void move(int deltax, int deltay) {
x1 += deltax; x2 += deltax;
y1 += deltay; y2 += deltay;
}
/** Test whether the specified point is inside the rectangle */
public boolean isInside(int x, int y) {
return ((x >= x1) && (x <= x2) && (y >= y1) && (y <= y2));
}
/**
* Return the union of this rectangle with another. I.e. return the
* smallest rectangle that includes them both.
