Java/Language Basics/Object Oriented Design

Class Hierachy

   <source lang="java">

/*

* Copyright (c) Ian F. Darwin, http://www.darwinsys.ru/, 1996-2002.
* All rights reserved. Software written by Ian F. Darwin and others.
* $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS""
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* 
* Java, the Duke mascot, and all variants of Sun"s Java "steaming coffee
* cup" logo are trademarks of Sun Microsystems. Sun"s, and James Gosling"s,
* pioneering role in inventing and promulgating (and standardizing) the Java 
* language and environment is gratefully acknowledged.
* 
* The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
* inventing predecessor languages C and C++ is also gratefully acknowledged.
*/

import java.util.*; /** Part of a main program using Shape objects */ public class ClassShapeMain {

 Collection allShapes;  // created in a Constructor, not shown
 /** Iterate over all the Shapes, getting their areas */
 public double totalAreas() {
   Iterator it = allShapes.iterator();
   double total = 0.0;
   while (it.hasNext()) {
     Shape s = (Shape)it.next();
     total += s.ruputeArea();
   }
   return total;
 }

} class Circle extends Shape {

 double radius;
 public double computeArea() {
   return Math.PI * radius * radius;
 }

} class Rectangle extends Shape {

 double width, height;
 public double computeArea() {
   return width * height;
 }

} abstract class Shape {

 protected int x, y;
 public abstract double computeArea();

}

      </source>
   
  
 
  

Hierarchy 2

   <source lang="java">

/*

* Copyright (c) Ian F. Darwin, http://www.darwinsys.ru/, 1996-2002.
* All rights reserved. Software written by Ian F. Darwin and others.
* $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS""
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* 
* Java, the Duke mascot, and all variants of Sun"s Java "steaming coffee
* cup" logo are trademarks of Sun Microsystems. Sun"s, and James Gosling"s,
* pioneering role in inventing and promulgating (and standardizing) the Java 
* language and environment is gratefully acknowledged.
* 
* The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
* inventing predecessor languages C and C++ is also gratefully acknowledged.
*/

public class Customer extends Person {

 private int customerNumber;
 public Customer(String firstName, String lastName, int number) {
   super(firstName, lastName);
   setCustomerNumber(number);
 }
 public void setCustomerNumber(int n) {
   if (n < 1)
     throw new IllegalArgumentException("Invalid customer number " + n);
   customerNumber = n;
 }

} class Person {

 String firstName;
 String lastName;
 Person(String firstName, String lastName) {
   this.firstName = firstName;
   this.lastName = lastName;
 }

} class Employee extends Person {

 private short deptCode;
 private int staffNumber;
 public Employee(String firstName, String lastName, short dept, int number) {
   super(firstName, lastName);
   setDeptCode(dept);
   setStaffID(number);
 }
 public void setDeptCode(short dept) {
   deptCode = dept;
 }
 public void setStaffID(int number) {
   if (number < 1)
     throw new IllegalArgumentException("Invalid staff number " +
       number);
   staffNumber = number;
 }

}

      </source>
   
  
 
  

This class shows how we might control the objects

   <source lang="java">

/*

* Copyright (c) Ian F. Darwin, http://www.darwinsys.ru/, 1996-2002.
* All rights reserved. Software written by Ian F. Darwin and others.
* $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS""
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* 
* Java, the Duke mascot, and all variants of Sun"s Java "steaming coffee
* cup" logo are trademarks of Sun Microsystems. Sun"s, and James Gosling"s,
* pioneering role in inventing and promulgating (and standardizing) the Java 
* language and environment is gratefully acknowledged.
* 
* The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
* inventing predecessor languages C and C++ is also gratefully acknowledged.
*/

/**

* BuildingManagement - control an energy-saving building.
* This class shows how we might control the objects in an office
* that can safely be powered off at nighttime to save energy - lots of
* it, when applied to a large office!
*/

public class BuildingManagement {

 Asset things[] = new Asset[24];  
 int numItems = 0;
 /** goodNight is called from a timer Thread at 2200, or when we
  * get the "shutdown" command from the security guard.
  */
 public void goodNight() {
   for (int i=0; i<things.length; i++)
     if (things[i] instanceof PowerSwitchable)
       ((PowerSwitchable)things[i]).powerDown();
 }
 // goodMorning() would be the same, but call each one"s powerUp().
 /** Add a Asset to this building */
 public void add(Asset thing) {  
   System.out.println("Adding " + thing);
   things[numItems++] = thing;
 }
 /** The main program */
 public static void main(String[] av) {
   BuildingManagement b1 = new BuildingManagement();
   b1.add(new RoomLights(101));  // control lights in room 101
   b1.add(new EmergencyLight(101));  // and emerg. lights.
   // add the computer on desk#4 in room 101
   b1.add(new ComputerCPU(10104));
   // and its monitor
   b1.add(new ComputerMonitor(10104));
   // time passes, and the sun sets...
   b1.goodNight();
 }

} abstract class BuildingLight extends BuildingAsset {

 // generic info on lighting: flourescent/incandescent, ...
 BuildingLight(int roomNumber) {
   super(roomNumber);
 }

} abstract class ComputerAsset extends Asset {

 // generic computer component stuff here: location, owner, 
 // warranty expiration date :-), etc.
 int deskNumber;
 ComputerAsset(int deskNumber) {
   this.deskNumber = deskNumber;
 }

} class ComputerCPU extends ComputerAsset {

 // information about CPU (P5, P6, ...), RAM, etc.
 ComputerCPU(int deskNumber) {
   super(deskNumber);
 }

} /** Asset is the top level of every Asset */ abstract class Asset extends Object {

 // No fields or methods; it"s just the base of everything.

} class EmergencyLight extends BuildingLight { // NEVER SWITCH OFF

 EmergencyLight(int roomNumber) {
   super(roomNumber);
 }

} /**

* PowerSwitchable is an Interface that will be implemented by things
* that can safely be turned off at night. Could use X10(tm) or BlueTooth
* or 802.11 or any similar network technology to turn things on or off.
*
* @author  Ian F. Darwin
*/

interface PowerSwitchable {

 /** The technique for turning this unit off */
 public void powerDown();
 /** The technique for turning this unit on */
 public void powerUp();

} class RoomLights extends BuildingLight implements PowerSwitchable {

 RoomLights(int roomNumber) {
   super(roomNumber);
 }
 public void powerDown() {
   System.out.println("Dousing lights in room " + room);
 }
 public void powerUp() {
   System.out.println("Lighting lights in room " + room);
 }

} /** The top level of everything that is permanently part of the building */ abstract class BuildingAsset extends Asset {

 protected int room;
 public BuildingAsset(int room) {
   this.room = room;
 }

} class ComputerMonitor extends ComputerAsset implements PowerSwitchable {

 ComputerMonitor(int roomNumber) {
   super(roomNumber);
 }
 public void powerDown() {
   System.out.println("Dousing monitor at desk " + deskNumber);
   // send the code to the Monitor"s X10 box to shut it off
 }
 public void powerUp() {
   System.out.println("Warming up monitor at desk " + deskNumber);
   // send the code to the Monitor"s X10 box to turn it on
 }

}

      </source>