For 2023 (and 2024 ...) - we are now fully retired from IT training. We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.
Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!
I am also active in many other area and still look after a lot of web sites - you can find an index ((here)) |
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 [656] Think about your design even if you don't use full UML - (2006-03-24) [831] Comparison of Object Oriented Philosophy - Python, Java, C++, Perl - (2006-08-13) [1066] Final, Finally and Finalize - three special words in Java - (2007-02-05) [1217] What are factory and singleton classes? - (2007-06-04) [1294] An example of Java Inheritance from scratch - (2007-08-00) [1501] Java - using super to call a method in the parent class - (2008-01-10) [1538] Teaching Object Oriented Java with Students and Ice Cream - (2008-02-12) [1819] Calling base class constructors - (2008-10-03) [2185] Abstract Classes - Java - (2009-05-16) [2434] Abstract classes, Interfaces, PHP and Java - (2009-10-03) [2604] Tips for writing a test program (Ruby / Python / Java) - (2010-01-29) [2860] What methods are available on this Java object? - (2010-07-08) [3047] What is a universal superclass? Java / Perl / Python / Other OO languages - (2010-11-13) [4334] Splitting out code into name blocks for clarity and reusability - (2014-11-30) [4366] Changing what operators do on objects - a comparison across different programming languages - (2014-12-26) [4394] Philosophy behind object design - and how I applied in to a Java example - (2015-01-14) [4419] Java Inheritance example - group of classes - step by step - (2015-02-08) [4422] Objects - from physical to virtual or abstract - Java - (2015-02-10)
Some other Articles
HST Power Car TravelWatch SouthWestCalling on Melksham / Trowbridge / Devizes / Chippenham businessesGetting somewhere with the train serviceTrying out our Java examples on our web siteJava - a demonstration of inheritance on just one pageAdvanced Python, Perl, PHP and Tcl training courses / classesOnline hotel reservations - Melksham, Wiltshire (near Bath)Automatic startup and shutdown of TomcatExtra public classes in deploying Apache httpd and TomcatWhich modules are loaded in my Apache httpd
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This is a page archived from The Horse's Mouth at
http://www.wellho.net/horse/ -
the diary and writings of Graham Ellis.
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