Essential Java Fast : How to write object oriented software for the Internet

196 Pages·1997·12.859 MB·English

by  John Cowell BSc(Hons), MPhil.,PhD. (auth.)

Essential Java Fast
How to write object oriented software for the Internet
Springer-Verlag London Ltd.
John Cowell
Essential
Java Fast
How to write object oriented
software for the Internet
with 64 figures
Springer
John Cowell, BSc(Hons), MPhil.,PhD.
Department of Computer and Information Sciences, De Montfort University
Kents Hill Campus, Hammerwood Gate, Kents Hill
Milton Keynes. MK7 6HP, UK
ISBN 978-3-540-76052-8
British Library Cataloguing in Publication Data
Cowell, John, 1957-
Essential Java fast: how to write object oriented software for the Internet in Java
l.Java (Computer program language) 2.0bject-oriented programming (Computer science)
3.Internet (Computer network)
I.Titie
005.1' 33
ISBN 978-3-540-76052-8 ISBN 978-1-4471-0629-6 (eBook)
DOI 10.1007/978-1-4471-0629-6
Library of Congress Cataloging-in-Publication Data
A Catalog record for this book is available from the Library of Congress
Apart from any fair dealing for the purpose of research or private study, or criticism or review,
as permitted under the Copyright, Designs and Patents Act 1989, this publication may only be
reproduced, stored or transmitted, in any form or by any means, with the prior permission in
writing of the publishers, or in the case of reprographic reproduction in accordance with the
terms of licences issued by the Copyright Licensing Agency. Enquiries concerning
reproduction outside those terms should be sent to the publishers.
© Springer-Verlag London 1997
Originally published by Springer-Verlag Berlin Heidelberg New York in 1997
Microsoft, MS, Visual Basic, Windows and Windows 95 are trademarks of Microsoft
Corporation Ltd.
Delphi is a trademark of Borland Corporation Ltd.
Java and Hot Java are trademarks of Sun Microsystems Corporation Ltd.
The use of registered names, trademarks etc. in this publication does not imply, even in the
absence of a specific statement, that such names are exempt from the relevant laws and
regulations and therefore free for general use.
The publishers make no representation, express or implied, with regard to the accuracy of the
information contained in this book and cannot accept any legal responsibility or liability for
anyerrors or omissions that may be made.
Typesetting: camera-ready by author
34/3830-543210. Printed on acid-free paper
Contents
1 WHY USE JAVA? ......................................................................................... 1
Introduction .............................................................................................. 1
What is Java? ........................................................................................... 2
Is this book for you? ................................................................................. 2
What you need to run Java ....................................................................... 3
How to use this book ................................................................................ 3
Conventions .............................................................................................. 4
2 OBJECT ORIENTATION PRIMER ............................................................... 5
Introduction .............................................................................................. 5
What are objects? ..................................................................................... 5
Classes ...................................................................................................... 6
Attributes and behaviour .......................................................................... 7
Inheritance ................................................................................................ 8
Why use inheritance? ............................................................................... 8
3 JAVA APPLETS ......................................................................................... 10
Introduction ............................................................................................ 10
Applets and applications ......................................................................... 10
Why applets are different ....................................................................... 11
A simple applet. ...................................................................................... 13
Initialising an applet ............................................................................... 13
Starting an applet .................................................................................... 14
Stopping an applet .................................................................................. 14
Destroying an applet. .............................................................................. 14
Displaying text and graphics .................................................................. 14
Java and HTML ...................................................................................... 15
HTML tags ............................................................................................. 16
The applet tag ......................................................................................... 16
Creating an applet. .................................................................................. 17
Controlling the applet size and position ................................................. 18
Compiling applications ........................................................................... 21
Command line arguments for applications ............................................. 21
Command line arguments for applets ..................................................... 21
v
vi Contents
4 THE JAVA LANGUAGE ..............................................................................2 4
Introduction ............................................................................................. 24
Applications and applets ......................................................................... 24
Features of Java programs ....................................................................... 25
Names in Java ......................................................................................... 25
Running a Java application ..................................................................... 25
Key elements of a Java program ............................................................. 26
Classes ..................................................................................................... 26
New objects ............................................................................................. 27
Data types ................................................................................................ 27
Arrays ...................................................................................................... 28
Methods ................................................................................................... 29
Calling methods ...................................................................................... 30
Creating a class and an object ................................................................. 31
Instance variables .................................................................................... 32
Class variables ......................................................................................... 33
Constants ................................................................................................. 33
Using instance variables .......................................................................... 33
Using class variables ............................................................................... 34
The keyword this ..................................................................................... 35
Arithmetic in Java ................................................................................... 35
Assigning number variables .................................................................... 35
Casting .................................................................................................... 36
Assigning characters, strings and boolean variables ............................... 36
Assignment operators .............................................................................. 37
Assigning objects .................................................................................... 39
Comparison operators ............................................................................. 39
Comparing objects .................................................................................. 40
Overloaded methods ................................................................................ 40
Constructors ............................................................................................ 41
The finalize method ................................................................................ .4 2
5 BRANCHING AND LOOPiNG ..................................................................... 43
Introduction ............................................................................................. 43
If .. else statements .................................................................................. .43
Block statements ..................................................................................... 44
The conditional operator ........................................................................ .45
Switch statements .................................................................................... 45
Looping ................................................................................................... 46
While loops .............................................................................................. 46
Do .. while loops ....................................................................................... 47
For loops ................................................................................................. 47
Quitting loops .......................................................................................... 48
Java operators ........................................................................................... 49
Bitwise operators ..................................................................................... 49
Contents vii
Logical operators .................................................................................... 51
Operator precedence ............................................................................... 52
Using strings in Java ............................................................................... 53
6 GRAPHiCS ................................................................................................. 55
Introduction ............................................................................................ 55
Graphics basics ....................................................................................... 55
Graphics drawing methods ..................................................................... 57
Lines and points ...................................................................................... 57
Rectangles .............................................................................................. 57
Plain rectangles ....................................................................................... 58
Rounded rectangles ................................................................................ 58
3D-effect rectangles ................................................................................ 59
Polygons ................................................................................................. 60
Ovals ...................................................................................................... 61
Arcs ........................................................................................................ 62
Colour ..................................................................................................... 63
Pre-defined colour .................................................................................. 63
Defining colours ..................................................................................... 64
Changing object colours ......................................................................... 64
Text and fonts ......................................................................................... 66
Using images .......................................................................................... 67
The draw/mage method .......................................................................... 68
The keyword this .................................................................................... 69
7 ANIMATION AND MULTITHREADING ...................................................... 70
Introduction ............................................................................................ 70
Multithreading ........................................................................................ 70
Creating new threads .............................................................................. 71
Pre-emptive scheduling .......................................................................... 72
Problems with multiple threads .............................................................. 74
The synchronized keyword ..................................................................... 75
Using Runnable ...................................................................................... 76
Thread priorities ..................................................................................... 76
Animation ............................................................................................... 78
The bouncing ball applet ........................................................................ 78
Using threads .......................................................................................... 80
Reducing flicker ..................................................................................... 83
Overriding methods ................................................................................ 83
Overriding update .................................................................................. 84
Using double buffering ........................................................................... 86
viii Contents
8 HANDLING EXCEPTIONS .......................................................................... 92
Introduction ............................................................................................. 92
What are exceptions? .............................................................................. 92
Java exceptions ....................................................................................... 92
The java.lang .Exception class ................................................................. 93
Trying and catching ................................................................................. 94
Throwing and catching ............................................................................ 96
Usingfinally ............................................................................................ 96
9 THE JAVA.AWl PACKAGE ........................................................................ 97
Introduction ............................................................................................. 97
Event driven programming ...................................................................... 97
What the AWT does ................................................................................ 98
The Button component ............................................................................ 98
The Label component. ........................................................................... l 00
The Scrollbar component. ..................................................................... l 00
The Checkbox component ..................................................................... 10 2
The List component. .............................................................................. l 03
The TextField component ..................................................................... 104
Entering passwords ............................................................................... l 05
The TextArea component ...................................................................... 105
Controlling layout ................................................................................. 106
The FlowLayout class ........................................................................... 106
The GridLayout class ............................................................................ 107
The GridBagLayout cIass ...................................................................... 10 8
The BorderLayout class ........................................................................ 110
The CardLayout class ........................................................................... 111
Layout methods ..................................................................................... 112
Using the layout managers .................................................................... 112
10 HANDLING EVENTS .............................................................................. 116
Introduction ........................................................................................... 116
. Mouse events ......................................................................................... 116
The mouseDown and mouse Up events .................................................. 117
Boolean methods ................................................................................... 118
The line drawing applet.. ....................................................................... 118
The scribble applet ................................................................................ 120
Keyboard events .................................................................................... 122
The handleEvent method ...................................................................... 124
The action method ................................................................................ 125
11 WINDOWS, DIALOGS AND MENUS ...................................................... 128
Introduction ........................................................................................... 128
Contents ix
Creating and displaying windows ......................................................... 128
Adding objects to pages ....................................................................... 129
Menus ................................................................................................... 130
Types of menu items ....................................................................... : ..... 132
Enabling and disabling menu items ...................................................... 134
The Dialog subclass ............................................................................. 134
Windows methods ................................................................................ 135
12 INPUT AND OUTPUT STREAMS .......................................................... 137
Introduction .......................................................................................... 137
The java.io package .............................................................................. 137
The FilelnputStream class .................................................................... 138
Reading from streams ........................................................................... 140
The skip and mark methods .................................................................. 140
The ByteArraylnputStream class .......................................................... 141
The StringBuJferlnputStream class ....................................................... 141
The FilterlnputStream class ................................................................. 142
The BuJferedlnputStream class ............................................................ 142
The DatalnputStream class .................................................................. 142
The LineNumberlnputStream class ...................................................... 143
The PushbacklnputStream class ........................................................... 144
The PipedlnputStream class ................................................................. 144
The SequencelnputStream class ........................................................... 144
The OutputStream class ........................................................................ 145
The FileOutputStream class ................................................................. 145
Writing to streams ................................................................................ 146
The ByteArrayOutputStream class ....................................................... 147
The FilterOutputStream class ............................................................... 147
The BuJferedOutputStream class .......................................................... 148
The PrintStream class .......................................................................... 148
The DataOutputStream class ................................................................ 149
The PipedOutputStream class .............................................................. 150
13 MODIFIERS AND PACKAGES .............................................................. 151
Introduction .......................................................................................... 151
Access control ...................................................................................... 151
The public access modifier ................................................................... 152
The private access modifier .................................................................. 152
The package access modifier.. .............................................................. 153
The protected access modifier .............................................................. 153
Accessor methods ................................................................................. 153
Thefinal modifier ................................................................................. 154
Using packages ..................................................................................... 155
Why use packages? .............................................................................. 155
x Contents
Importing packages ............................................................................... 157
The java. lang package .......................................................................... 158
14 JAVA AND C++ ....................................................................................... 159
Introduction ........................................................................................... 159
Data types .............................................................................................. 159
Using strings .......................................................................................... 160
Command line arguments ...................................................................... 160
Exception handling ................................................................................ 160
Miscellaneous differences ..................................................................... 161
APPENDIX AJ AVA PACKAGES ................................................................. 162
Introduction ........................................................................................... 162
Reserved words ..................................................................................... 162
Reserved characters ............................................................. :. ................ 162
Java operators ........................................................................................ 163
Java data types ...................................................................................... 163
The Java class library ............................................................................ 164
The java.awt package ............................................................................ 164
Exception index for java.awt ................................................................ 166
The java.awt.image package ................................................................. 166
Exception index for java.awt.image ...................................................... 166
The java.awt.peer package .................................................................... 167
Exception index for java.awt.peer ........................................................ 167
The java.io package .............................................................................. 167
Exception index for java.io ................................................................... 169
The java. lang package .......................................................................... 169
Exception index for java. lang ............................................................... 170
The java.util package ............................................................................ 171
Exception index for java.util ................................................................. 172
The java. net package ............................................................................. 172
Exception index for java.net ................................................................. 173
The java.applet package ....................................................................... 173
Exception index for java.applet ............................................................ 173
APPENDIX B CLASS HIERARCHIES .......................................................... 174
Introduction ........................................................................................... 174
Class hierarchy ...................................................................................... 174
INDEX .......................................................................................................... 183