Main Content

Java - a demonstration of inheritance on just one page

Archive - Originally posted on "The Horse's Mouth" - 2008-02-26 23:15:20 - Graham Ellis

Here's a challenge, just given to me by my Java Delegates, to put my complete example of a Rectangle and a a Circle class, both inheriting from a Shape base class, and a test harness ... on on a single screen. A bit tight, and a bit uncommented, but here it is!


public class Circle extends Shape {

	int w;

	public Circle (String col,int w) {

		super(col); this.w = w; }

	public int getarea () {

		return (int)(w * w * 0.25 * 3.14159265); } }

// --------------------------- 

public class Rectangle extends Shape {

	int w; int h;

	public Rectangle (String col,int w, int h) {

		super(col); this.w = w; this.h = h; }

	public int getarea () {

		return h * w; } }

// ---------------------------

public class Shape {

	private String colour; private static int nshapes = 0;

	public Shape(String colour) {

		this.colour = colour; nshapes ++; }

	public String getcolour() {

		return colour; }

	public static int getcount() {

		return nshapes; } }

// ---------------------------

public class Tablemats {

	public static void main (String [] args) {

	Rectangle Salisbury = new Rectangle("Orange",30,20);

	Circle Bath = new Circle("Purple",25);

	String scol = Salisbury.getcolour();

	int sarea = Salisbury.getarea(); String bcol = Bath.getcolour();

	int barea = Bath.getarea(); int nmats = Shape.getcount();

	System.out.println(scol); System.out.println(sarea);

	System.out.println(bcol); System.out.println(barea);

	System.out.println(nmats); } }


Now - they have to come up with two types of animals - Pets and Farm Animals - where a pet has a specified value and a farm animal has a value PER KILO.