Table Of Content

Applied Computing Springer London Berlin Heidelberg New York Barcelona Budapest Hong Kong Milan Paris Santa Clara Singapore Tokyo The Springer-Verlag Series on Applied Computing is an advanced series of innovative textbooks that span the full range of topics in applied computing technology. Books in the series provide a grounding in theoretical concepts in computer science alongside real-world examples of how those concepts can be applied in the development of effective computer systems. The series should be essential reading for advanced undergraduate and postgraduate students in computing and information systems. Books in the series are contributed by international specialist researchers and educators in applied computing who draw together the full range of issues in their specialist area into one concise authoritative textbook. Titles already available: Deryn Graham and Anthony Barrett Knowledge-Based Image Processing Systems Linda Macaulay Requirements Engineering Derrick Morris, Gareth Evans, Peter Green, Colin Theaker Object Oriented Computer Systems Engineering Forthcoming titles include: Jan Noyes and Chris Baber Designing Systems Derek Wills and Rob Macredie Applied Computer Graphics David Gray Real Time Systems Design John Hunt Java and Object Orientation: An Introduction Springer John Hunt, BSc, PhD, MBCS, CEng Department of Computer Science, University of Wales, Aberystwyth, Ceredigion SY 23 3DB, UK Series Editors Professor Peter J. Thomas, BA (Hons), PhD, AI Mgt, FRSA, FVRS Centre for Personal Information Management, University of the West of England, Coldharbour Lane, Bristol, BS16 lQY, UK Professor Ray J. Paul, BSc, MSc, PhD Department of Computer Science and Information Systems at st. John's, BruneI University, Kingston Lane, Uxbridge, Middlesex UB8 3PH, UK British Library Cataloguing in Publication Data Hunt,John Java and object orientation: an introduction. -(Applied computing) l.Java (Computer program language) 2.0bject-oriented programming (Computer science) I.Title 005·7'12'62 ISBN-13: 978-3-540-76201-0 e-ISBN-13: 978-1-4471-3380-3 DOl: 10.1007/978-1-4471-3380-3 Library of Congress Cataloging-in-Publication Data Hunt, John, 1964- Java and object orientation: an introduction / John Hunt. p. cm. --(Applied computing) Includes bibliographical references and index. ISBN-1J: 978-3-540-76201-0 I.Java (Computer program language) 2.0bject-oriented programming I.Title. ILSeries. QA76.nJ38H86 1997 00S.13'3-dc21 97-29238 Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, iliis publication may only be reproduced, stored or transmitted, in any form or by any means, with ilie prior permission in writing of ilie publishers, or in ilie case of repro graphic 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 Limited 1998 The use of registered names, trademarks etc. in this publication does not imply, even in the absence of a specific statement, iliat such names are exempt from the relevant laws and regulations and therefore free for general use. The publisher makes 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 any errors or omissions iliat may be made. Typesetting: Mitcham Editorial Services, Mitcham, Surrey 3413830-543210 Printed on acid-free paper This book is dedicated with love to my wife, Denise, and our daughter, Phoebe Preface This book was originally written to support an introductory course in Object Orientation through the medium of Java (and the Sun Java Development Kit, in particular) for those with experience of a procedural programming language such as C or Pascal. However, it can be used as a book to teach the reader Java, or to introduce object orientation, as well as to present object oriented design and analysis. It takes as its basic premise that most computer scientists and software engineers learn best by doing rather than reading theoretical discussions. The chapters therefore attempt to introduce concepts by getting you, the reader, to do things, rather than by extensive theoretical discussion. This means that the chapters take a hands-on approach to the subject and assume that you have a suitable Java environment available. The chapters are listed below and are divided into eight parts. You are advised to work through Parts 1 and 3 thoroughly in order to gain a detailed understanding of object orientation. Parts 2 and 4 introduce the Java language. You may then dip into other chapters as required. For example, if you wish to hone your Java skills then the chapters in Part 6 will be useful, whereas if you wish to gain an overview of object oriented design then you may prefer to read Part 7. However, if you wish to discover the delights of graphical user interfaces in Java, then you should read Part 5 next. CONTENT SUMMARY Part 1: Introduction to Object Orientation Chapter 1: Introduction to Object Orientation This chapter introduces the range of concepts and ideas, which make up object technology. It presents the background that led to the acceptance of object orientation as a mainstream technology and discusses the pedigree of the Java language. viii Java and Object Orientation Chapter 2: Elements of Object Orientation This chapter provides a more formal definition of the terminology introduced in Chapter 1. It also considers the advantages and disadvantages of an object oriented approach compared to more traditional procedural approaches. Chapter 3: Constructing an Object Oriented System A typical problem for many people when being introduced to a new approach is that they understand the terminology and the concepts but not how to use them. This chapter aims to alleviate this problem by presenting a detailed worked example of the way in which an object oriented system may be designed and constructed. It does so without reference to any particular language, so that language issues do not confuse the discussion. Part 2: Introduction to the Java Language Chapter 4: A Brief History of Time, the Universe and Java This chapter provides some background on the history of Java and the development environments which are available to support it (such as the Sun Java Development Kit). It also considers some of the tools that you will encounter. Chapter 5: A Little Java This chapter introduces the Java syntax, and examines the structure of a basic Java application. Chapter 6: Java Building Blocks This chapter considers classes, instances, methods and variables as well as interface specifications in Java. These are the basic building blocks of any object oriented program and in particular of a Java program. Chapter 7: Java Constructs This chapter presents further details of the Java language, including numbers, operators, variables and message passing. This chapter also looks at the String, Integer and Character classes. Chapter 8: An Example Java Class This chapter presents you with a detailed worked example of software development in Java. This example presents a very simple class definition which uses only those concepts which have been introduced at this stage. The intention is to illustrate how the constructs and language elements can be combined in a real (if simple) application. Preface ix Part 3: Java and Object Orientation Chapter 9: Classes, Inheritance and Abstraction This chapter considers how you should use inheritance, abstraction and classes in Java. It considers the role of classes and when to create subclasses and define abstract classes. Chapter 10: Encapsulation and Polymorphism This chapter considers how to achieve encapsulation in Java. It considers how the visibility of methods and variables can be modified. It presents packages and how they are defined and used. It also discusses issues associated with the polymorphic appearance of Java. Chapter 11: Data Structures This chapter discusses the Java classes which are used to construct data structures. These classes include Array, Vector and Hashtable. Chapter 12: Defining Collection Classes This chapter considers how to create further data structure classes, such as Sets and Ordered Collections. It introduces interfaces as a way of ensuring a common set of facilities and enabling the generic use of such classes. It concludes by describing enumerations and their use. Part 4: Further Java Chapter 13: Control and Iteration This chapter introduces control and iteration in Java. Chapter 14: An Object Oriented Organizer This chapter presents a detailed example application constructed using the Vector class. The application is an electronic personal organizer that contains an address book, a diary (or appointments section) and a section for notes. The remainder of this chapter describes one way of implementing such an organizer. At the end of this chapter is a programming exercise. Chapter 15: Streams and Files This chapter discusses the other most common class hierarchies in Java, the Stream classes. The Stream classes are used (amongst other things) for accessing files. Chapter 16: Serialization This chapter explains how objects can be stored to file and restored from file using serialization. This provides a very basic persistent object system for Java. x Java and Object Orientation Chapter 17: Observers and Observables The Observer interface and Observable class are used to implement the Java dependency mechanism. This mechanism allows one or more objects to be informed about changes in the state of an object, without that object knowing anything about the first set of objects. It is particularly important in the construction of reusable, object oriented, graphical user interfaces. Part 5: Graphical Interfaces and Applets Chapter 18: Graphic Programming Using the AWT The Abstract Window Toolkit (A WT) is a platform-independent set of classes for constructing graphical interfaces. This chapter looks at how to construct windows and generate graphics. Chapter 19: User Interface Programming This chapter considers the Java Delegation Event Model and the range of GUI construction classes in the AW T. Chapter 20: Managing Component Layout This chapter introduces the layout managers provided with the AWT. These objects control how components are laid out within an interface in a portable and useful manner. Chapter 21: A GUI Case Study This chapter describes a detailed worked example of how to construct a user interface for the organizer application developed in Chapter 14. Chapter 22~ Combining Graphics and GUI Components This chapter brings together the graphic elements of the AW T described in Chapter 18 with the user interface components described in Chapters 19 to 21. Chapter 23: Applets and the Internet This chapter examines the facilities in Java for programming for the Internet. It introduces applets and URLs. Part 6: Java Development Chaptp.r 24: Java Style Guidelines This chapter aims to promote readable, understandable, concise and efficient Java code. Preface xi Chapter 25: Exception Handling In Java, exceptions are objects (just like almost everything else). Thus, to throw an exception you must first make an instance of an exception class. This chapter considers exceptions and how to create, throw and handle them. It also discusses defining new exceptions by creating subclasses. Chapter 26: Concurrency This chapter describes the concurrency mechanism of Java. That is, it describes the way in which Java implements lightweight threads. Part 7: Object Oriented Design Chapter 27: Object Oriented Analysis and Design This chapter introduces the concepts of object oriented analysis and design. It reviews a number of the more popular techniques such as OOA, OMT, Objectory and Booch. It also briefly considers the unification of the OMT and Booch notations. Chapter 28: The Unified Modeling Language The Unified Modeling Language (UML) is a third generation object oriented modeling language which adapts and extends the published notations used in the Booch, OMT and Objectory methods. UML is intended to form a single, common" widely used modeling language for a range of object oriented design methods (including Booch, Objectory and OMT). It should also be applicable to a wide range of applications and domains. This chapter summarizes the UML notation. Chapter 29: The Object Modeling Technique This chapter discusses the influential design method referred to as the Object Modeling Technique (OMT). It summarizes the main phases of OMT using the UML notation. An extension to OMT introduces use case models from Objectory to improve the requirements analysis process. This is motivated by the inclusion of use case diagrams in UML. Part 8: The Future Chapter 30: Areas of Java and Object Technology not Covered Java has many features which are not suitable for an introductory book. This chapter attempts to make you aware of what has not been covered, without going into any detail. It includes discussion of the current developments within the Java world. In particular, it introduces the Java Beans (component) model, and discusses the RMI (Remote