Java/Language Basics/Object Oriented Design
Class Hierachy
/*
* 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();
}
Hierarchy 2
/*
* 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;
}
}
This class shows how we might control the objects
/*
* 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
}
}
