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JAVA FOR STUDENTS

4TH EDITION

DOUGLAS BELL AND MIKE PARR

PREFACE

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About this book

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Contents

Preface

Updates, errors

Sample Chapters

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Preface

 

·        What this book will tell you

This book explains how to write Java programs that run either as independent applications or as applets (part of a web page).

 

·        This book is for novices

If you have never done any programming before if you are a complete novice this book is for you. This book assumes no prior knowledge of programming. It starts from scratch. It is written in a simple, direct style for maximum clarity. It is aimed primarily at first year undergraduates at universities and colleges, but it is also suitable for novices studying alone.

 

·        Why Java?

Java is probably one of the best programming languages to learn and use because of the following features.

 

Java is small and beautiful

The designers of Java have deliberately left out all the superfluous features of programming languages; they cut the design to the bone. The result is a language that has all the necessary features, combined in an elegant and logical way. The design is lean and mean. It is easy to learn, but powerful.

 

Java is object-oriented

Object-oriented languages are the latest and most successful approach to programming. Object-oriented programming is the most popular approach to programming. Java is completely object-oriented from the ground up. It is not a language that has had object-orientedness grafted onto it as an afterthought.

 

Java supports the Internet

A major motivation for Java is to enable people to develop programs that use the Internet and the World-Wide Web. Java applets can easily be invoked from Web browsers such as Internet Explorer to provide valuable and spectacular facilities. In addition, Java programs can be easily transmitted around the Internet and run on any computer.

 

Java is general-purpose

Java is a truly general-purpose language. Anything that C++, Visual Basic etc. can do, so can Java.

 

Java is platform-independent

Java programs will run on almost all computers and with nearly all operating systems unchanged! Try that with any other programming language. (You almost certainly can't!) This is summed up in the slogan "write once run anywhere".

 

Java is robust

The Java compiler carries out many stringent checks as it prepares a program for execution. Once a program has been corrected and compiles without errors, it often performs correctly. However, if a Java program goes wrong (and programs do have that tendency), it won't create mayhem, damage and uncertainty.

 

Java has libraries

Because Java is a small language, most of its functionality is provided by pieces of program held in libraries. A whole host of library software is available to do graphics, access the Internet, provide graphical user interfaces (GUIs) and many other things.

 

·        You will need

To learn to program you need a computer and some software. A typical system is a PC (personal computer) with the Java Software Development Kit (SDK). This is also available for Unix, GNU/Linux and Apple systems. This kit allows you to prepare and run Java programs. There are also more convenient development environments. We provide the SDK and additional software on the accompanying CD-ROM .

 

·        Exercises are good for you

If you were to read this book time and again until you could recite it backwards, you still wouldn't be able to write programs. The practical work of writing programs and program fragments is vital to becoming fluent and confident at programming.

  There are exercises for the reader at the end of each chapter. Please do some of them to enhance your ability to program.

  There are also short self-test questions with answers throughout the text, so that you can check you have understood things properly.

 

·        What's included?

This book explains the fundamentals of programming:

 

·        variables;

·        assignment;

·        input and output;

·        calculation;

·        graphics and windows programming;

·        selection using if;

·        repetition using while.

 

It also covers integer numbers, floating-point numbers and character strings. Arrays are also described. All these are topics that are fundamental, whatever kind of programming you go on to do.

  This book also thoroughly addresses the object-oriented aspects of programming:

 

·        using library classes.

·        writing classes;

·        using objects;

·        using methods;

 

We also look at some of the more sophisticated aspects of object-oriented programming, like:

 

·        inheritance;

·        polymorphism;

·        interfaces

 

·        What's not included

This book describes the essentials of Java. It does not explain the bits and pieces, the bells and whistles. Thus the reader is freed from unnecessary detail and can concentrate on mastering Java and programming in general.

 

·        Applications or Applets?

There are two distinct types of Java program:

 

·        a distinct free-standing program (this is called an application);

·        a program invoked from a Web browser (this is called an applet).

 

In this book we concentrate on applications, because we believe that this is the main way in which Java is being used. (We explain how to run applets in an appendix.)

 

·        Graphics or text?

Throughout the text we have emphasized programs that use graphical images rather than text input and output. We think they are more fun, more interesting and clearly demonstrate all the important principles of programming. We haven't ignored programs that input and output text they are included, but they come second best.

 

·        Graphical user interfaces (GUIs)

The programs we present use many of the features of a graphical user interface (GUI), such as windows, buttons, scrollbars and using the mouse in lots of different ways.

 

·        AWT or Swing?

There are two Java mechanisms for creating and using GUI's - AWT and Swing. The Swing set of user interface components is more complete and powerful than the AWT set. This book uses the Swing approach because it is being used more widely.

 

·        The sequence of material

Programming involves many challenging ideas, and one of the problems of writing a book about programming is deciding how and when to introduce new ideas. We introduce simple ideas early and more sophisticated ideas later on. We use objects from an early stage. Then later we see how to write new objects. Our approach is to start with ideas like variables and assignment, then introduce selection and looping, and then go on to objects and classes (the object-oriented features). We also wanted to make sure that the fun element of programming is paramount, so we use graphics right from the start.

 

·        Bit by bit

In this book we introduce new ideas carefully one-at-a-time, rather than all at once. So there is a single chapter on writing methods, for example.

 

·        Computer Applications

Computers are used in many different applications and this book uses examples from all these areas:

 

·        l               information processing;

·        l               games;

·        l               scientific calculations.

 

  The reader can choose to concentrate on those application areas of interest and spend less time on the other areas.

 

·        Different kinds of programming

There are many different kinds of programming examples are procedural, logic, functional, spreadsheet, visual and object-oriented programming. This book is about the dominant type of programming object-oriented programming as practiced in languages like Visual Basic, C++, C#, Eiffel and Smalltalk.

 

·        Which version of Java?

Java is evolving, but slowly. From time to time Sun release a new version of the Java Software Development Kit (SDK). A new version usually means additional items in the libraries - and a new version number. All versions from 1.2 have the generic name of Java 2. You can use this book with any version from version 1.2 onwards.

 

·        Have fun

Programming is creative and interesting, particularly in Java. Please have fun!

 

·        l Visit our Web site

All the programs presented in this book are available on our Web site, which can be reached via: www.booksites.net/bell.

 

 

·        Changes to this edition

 

If you have used earlier editions of this book, you might like to know what is different about this edition.

 

In making changes we have tried to keep to the sprit of the original and at the same time simplify things where possible. We have also tried to follow the main trends in using Java. So while the older edis used applets and the AWT for GUIs, this edition uses applications and Swing. The older editions used the method paint extensively and everyone find it difficult to understand. So we have eliminated paint to give major simplifications.

 

We have also made minor changes, such as using the term “call” rather than the long-winded term “invoke”. We have also used double variables instead of float because declaring literals is easier.

 

There used to be a chapter on applet architecture, but we were never sure that it worked. With the elimination of method paint and the simpler structure of applications, we don’t think this chapter is needed anymore. There was also a chapter on GUI components, which seemed out of place. So this chapter has been removed and incorporated within an improved appendix on the Java library, which presents sample programs.

 

The topic of abstract classes has been moved into the chapter on inheritance, where it rightly belongs. We have created a new chapter on array lists, which serves as an introduction to data structures.

 

We hope you like the changes.

 

 

·        Any comments on this book?

If you want to email the authors, we are at D.H.Bell@shu.ac.uk and M.Parr@shu.ac.uk. We look forward to hearing from you.