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Java - a demonstration of inheritance on just one page

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.
(written 2008-02-26, updated 2008-02-27)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
J710 - Java - Extending Classes and More
  [4422] Objects - from physical to virtual or abstract - Java - (2015-02-10)
  [4419] Java Inheritance example - group of classes - step by step - (2015-02-08)
  [4394] Philosophy behind object design - and how I applied in to a Java example - (2015-01-14)
  [4366] Changing what operators do on objects - a comparison across different programming languages - (2014-12-26)
  [4334] Splitting out code into name blocks for clarity and reusability - (2014-11-30)
  [3047] What is a universal superclass? Java / Perl / Python / Other OO languages - (2010-11-13)
  [2860] What methods are available on this Java object? - (2010-07-08)
  [2604] Tips for writing a test program (Ruby / Python / Java) - (2010-01-29)
  [2434] Abstract classes, Interfaces, PHP and Java - (2009-10-03)
  [2185] Abstract Classes - Java - (2009-05-16)
  [1819] Calling base class constructors - (2008-10-03)
  [1538] Teaching Object Oriented Java with Students and Ice Cream - (2008-02-12)
  [1501] Java - using super to call a method in the parent class - (2008-01-10)
  [1294] An example of Java Inheritance from scratch - (2007-08-00)
  [1217] What are factory and singleton classes? - (2007-06-04)
  [1066] Final, Finally and Finalize - three special words in Java - (2007-02-05)
  [831] Comparison of Object Oriented Philosophy - Python, Java, C++, Perl - (2006-08-13)
  [656] Think about your design even if you don't use full UML - (2006-03-24)


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