JAVA Developer's Guide

by Jamie Jaworski

C  O  N  T  E  N  T  S

Introduction

Chapter 1  The Java Phenomenon

• What Is Java?
• The Origins of Java
• Why Program in Java?
• Java and HotJava
• Summary

Chapter 2  Java Overview

• Getting the JDK
• A Quick Tour of the JDK
• The Java Language
  • Java Is Familiar and Simple
  • Java Is Object-Oriented
  • Java Is Safer and More Reliable
  • Java Is Secure
  • Java Is Multithreaded
  • Java Is Interpreted and Portable
  • Java Is the Programming Language of the Web
• The Java API
• Summary

Chapter 3  Using the Java Developer's Kit

• Overview
• The Compiler
  • Using Classes from Other Packages
  • Setting CLASSPATH
  • Changing the Root Directory
  • Generating Debugging Tables
  • Code Optimization
  • Suppressing Warnings
  • Using Verbose Mode
• The Interpreter
  • Changing CLASSPATH
  • Checking for Source Code Changes
  • Verifying Your Code
  • Controlling the Garbage Collector
  • Changing Properties
  • Setting Memory and Stack Limits
  • Debugging Options
• The Debugger
• The Disassembler
• The Applet Viewer
• Automating Software Documentation
• Header File Generation
• Running the Demo Programs
• Summary

Chapter 4  First Programs: Hello World! to BlackJack

• Hello World!
  • Comments
  • Java Program Structure
  • The package Statement
  • The import Statement
  • Classes and Methods
  • The System Class
• I Can Read!
  • Overview of ICanReadApp
  • Declaring Variables and Creating Objects
  • Identifiers and Keywords
  • Using System.in
• Type This!
  • Overview of TypeThisApp
  • The Primitive Java Data Types
  • Literal Values
• BlackJack
  • Overview of BlackJackApp
  • Arrays
  • Statements
• Summary

Chapter 5  Classes and Objects

• Object-Oriented Programming Concepts
  • It's an Object-Oriented World
  • Composition and Reuse
  • Classes
  • Classification and Inheritance
  • Multiple Inheritance
  • Messages, Methods, and Object Interaction
  • Encapsulation
  • Polymorphism
  • Dynamic Binding
• Java Classes
  • Class Syntax
  • The Point Class
  • Class Modifiers
  • Extending Superclasses
  • Adding Body to Classes
  • The CGrid Class
  • The CGObject Class
  • The PrintCGrid Class
  • The BorderedPrintCGrid Class
  • The CGPoint Class
  • The CGBox Class
  • The CGText Class
  • The KeyboardInput Class
  • The CDrawApp Program
  • Running CDrawApp
  • CDrawApp's Implementation of Object-Oriented Concepts
• Summary

Chapter 6  Interfaces

• The Purpose of Java Interfaces
• The Benefits of Interfaces
• Declaring Interfaces
• Implementing Interfaces
• The CDrawApp Interface Example
  • The CGTextEdit Interface
  • Updating the CGText Class
  • The CGTextPoint Class
  • The CGTextBox Class
  • Updating the CDraw Class
  • Running the Example
  • Example Summary
• Using Interfaces as Abstract Types
• Interface Constants
• Extending Interfaces
• Combining Interfaces
• Summary

Chapter 7  Exceptions

• Eliminating Software Errors
• Error Processing and Exceptions
• Throwing Exceptions
• Declaring Exceptions
• Declare or Catch?
• Using the try Statement
• Catching Exceptions
• Nested Exception Handling
• Rethrowing Exceptions
  • Analysis of NestedExceptionTest
• Summary

Chapter 8  Multithreading

• Understanding Multithreading
• How Java Supports Multithreading
  • Creating Subclasses of Thread
  • Implementing Runnable
• Thread States
• Thread Priority and Scheduling
• Synchronization
• Daemon Threads
• Thread Groups
• Summary

Chapter 9  Using the Debugger

• Overview of the Debugger
• An Extended Example
• Debugging Multithreaded Programs
• Summary

Chapter 10  Automating Software Documentation

• How javadoc Works
• Using javadoc
• Placing Doc Comments
• Using javadoc Tags
• Embedding Standard HTML
• Summary

Chapter 11  Language Summary

• The package Statement
• The import Statement
• Comments
• Identifiers
• Reserved Words
• Primitive Data Types and Literal Values
• Class Declarations
• Variable Declarations
• Constructor Declarations
• Access Method Declarations
• Static Initializers
• Interfaces
• Blocks and Block Bodies
• Local Variable Declarations
• Statements
  • Empty Statement
  • Block Statement
  • Method Invocation
  • Allocation Statements
  • Assignment Statements
  • The if Statement
  • Statement Labels
  • The switch Statement
  • The break Statement
  • The for Statement
  • The while Statement
  • The do Statement
  • The continue Statement
  • The synchronized Statement
  • The try Statement
  • The return Statement
• Operators
• Summary

Chapter 12  Portable Software and the java.lang Package

• The Object and Class Classes
  • Object
  • Class
  • A Touch of Class
• The ClassLoader, SecurityManager, and Runtime Classes
  • ClassLoader
  • SecurityManager
  • Runtime
• The System Class
  • Property-Related Methods
  • Security Manager-Related Methods
  • Runtime-Related Methods
  • Odds and Ends
  • Time and Properties
• Wrapped Classes
  • The Boolean Class
  • The Character Class
  • The Integer and Long Classes
  • The Double and Float Classes
  • The Number Class
  • All Wrapped Up
• The Math Class
• The String and StringBuffer Classes
  • String Literals
  • The + Operator and StringBuffer
  • String Constructors
  • String Access Methods
  • The StringBuffer Class
• Threads and Processes
  • Runnable
  • Thread
  • ThreadGroup
  • Process
  • Hello Again
• The Compiler Class
• Exceptions and Errors
  • The Throwable Class
  • The Error Class
  • The Exception Class
• Summary

Chapter 13  Stream-Based Input/Output and the java.io Package

• Streams
• The java.io Class Hierarchy
• The InputStream Class
  • The read() Method
  • The available() Method
  • The close() Method
  • Markable Streams
  • The skip() Method
• The OutputStream Class
  • The write() Method
  • The flush() Method
  • The close() Method
• Byte Array I/O
  • The ByteArrayInputStream Class
  • The ByteArrayOutputStream Class
  • The ByteArrayIOApp Program
  • The StringBufferInputStream Class
• File I/O
  • The File Class
  • The FileDescriptor Class
  • The FileInputStream Class
  • The FileOutputStream Class
  • The FileIOApp Program
• The SequenceInputStream Class
  • The SequenceIOApp Program
• Filtered I/O
  • The FilterInputStream Class
  • The FilterOutputStream Class
  • Buffered I/O
  • PushbackInputStream
  • The LineNumberInputStream Class
  • Data I/O
  • The PrintStream Class
  • Piped I/O
• The RandomAccessFile Class
  • The RandomIOApp Program
• The StreamTokenizer Class
  • The StreamTokenApp Program
• Summary

Chapter 14  Useful Tools in the java.util Package

• The Date Class
  • DateApp
• The Random Class
  • RandomApp
• The Enumeration Interface
• The Vector Class
  • VectorApp
• The Stack Class
  • StackApp
• The BitSet Class
  • BitSetApp
• The Dictionary, Hashtable, and Properties Classes
  • Dictionary
  • Hashtable
  • The Properties Class
• The StringTokenizer Class
  • TokenApp
• Observer and Observable
  • Observable
• Summary

Chapter 15  Window Programming with the java.awt Package

• Window Programming Classes
• Components and Containers
  • The Container Class
  • The Window Class
  • The Panel Class
  • The Label Class
  • The Button Class
  • The Checkbox Class
  • The Choice Class
  • The List Class
  • The TextComponent Class
  • The Canvas Class
  • The Scrollbar Class
• Constructing Menus
  • The MenuBar Class
  • The MenuItem Class
  • The Menu Class
  • The CheckboxMenuItem Class
  • The MenuContainer Class
• Organizing Windows
  • The LayoutManager Class
  • The BorderLayout Class
  • The CardLayout Class
  • The FlowLayout Class
  • The GridLayout Class
  • The GridBagLayout Class
• Handling Events
• Working with Images
  • The Color Class
  • The java.awt.image Package
  • The MediaTracker Class
• Geometrical Objects
  • The Point Class
  • The Rectangle Class
  • The Polygon Class
  • The Dimension Class
• Using Fonts
  • The FontMetrics Class
• Using the Toolkit
• Summary

Chapter 16  Web Programming With the java.applet Package

• Applets and the World Wide Web
  • The Applet Class
  • Applets and HTML
• The Life Cycle of an Applet
• Responding to Events
• Using Window Components
• Adding Audio and Animation
• Summary

Chapter 17  Network Programming with the java.net Package

• The Internet Protocol Suite
  • What Is the Internet and How Does It Work?
  • Connection-Oriented Versus Connectionless Communication
• Client/Server Computing and the Internet
  • Sockets and Client/Server Communication
• Overview of java.net
• The InetAddress Class
• The Socket Class
• The ServerSocket Class
• The DatagramSocket Class
• The DatagramPacket Class
  • TimeServerApp
  • GetTimeApp
• The SocketImpl Class and the SocketImplFactory Interface
• Web-Related Classes
  • URL
  • URLConnection
  • URLEncoder
• The ContentHandler and ContentHandlerFactory Classes
• The URLStreamHandler Class and the URLStreamHandlerFactory Interface
• Summary

Chapter 18  Opening Windows

• Hello Windows!
• Going Round in Ovals: A Graphics Program
• A Text Editor
• Summary

Chapter 19  Organizing Window Programs

• Designing Window Programs
• Opening and Closing Windows
• Using Layouts
• Connecting Code to Events
• The Window Sampler Program
  • MyTextField
  • MyButton
  • MyCanvas
  • MyCheckBoxGroup
  • MyChoice
  • MyList
  • MyScrollbar
• Summary

Chapter 20  Menus, Buttons, and Dialong Boxes

• Adding Menus to Windows
  • The MyMenu Class
  • The MyMenuBar Class
  • The MenuApp Program
• Working with Buttons
  • The ButtonBar Class
  • The ButtonApp Program
• Using Dialog Boxes
  • The MessageDialog Class
  • The MessageApp Program
  • The FileDialog Class
• Summary

Chapter 21  Checkboxes, Choices, and Lists

• Using Checkboxes
  • The CheckboxPanel Class
• Working with Radio Buttons
  • The CheckboxGroupPanel Class
• The CheckboxApp Program
• Making Choices
  • The MyChoice Class
• Selecting from Lists
  • The MyList Class
• The ChoiceListApp Program
• Summary

Chapter 22  Text and Fonts

• The Text Classes
• Font Basics
  • Using the Toolkit Class
  • The FontApp Program
• WYSIWYG Editors
  • The EditApp Program
  • The FontDialog Class
  • The ColorDialog Class
• Summary

Chapter 23  The Canvas

• The Canvas and Graphics Classes
• Displaying Bitmapped Images
  • The DisplayImageApp Program
• Drawing and Painting
  • The DrawApp Program
• Combining Graphics and Text
• The Image-Processing Classes of java.awt.image
  • The ImageApp Program
• Summary

Chapter 24  Scrollbars

• How Scrollbars Work
• Using Scrollbars
• Scrolling Text
  • The TextScrollApp Program
• Scrolling Graphics
  • The ImageScrollApp Program
• Summary

Chapter 25  Using Animation

• Animation Basics
• A Simple Animation
• A Graphics Animation
• Improving Animation Display Qualities
• An Updated Graphics Animation
• Summary

Chapter 26  Client Programs

• Types of Clients
• Client Responsibilities
• A Simple Telnet Client
  • The Network Virtual Terminal
  • The Interpret as Command Code
  • Negotiated Options
  • Symmetry Between Terminals and Processes
  • The TelnetApp Program
  • The NVTPrinter Class
  • The NVTInputStream Class
  • The NVTOutputStream Class
• A Mail Client
  • The MailClientApp Program
• The Web Fetcher Program
• Summary

Chapter 27  Server Programs

• Types of Servers
• Server Responsibilities
• An SMTP Server
  • The SMTPServerApp Program
• A Web Server
  • The WebServerApp Program
• Summary

Chapter 28  Content Handlers

• Using Content Handlers
• Multipurpose Internet Mail Extensions (MIME)
• Developing a Content Handler
• A Simple Content Handler
  • The GridContentHandler Class
  • The GetGridApp Program
• Summary

Chapter 29  Protocol Handlers

• Using Protocol Handlers
• Developing a Protocol Handler
• A Simple Protocol Handler
• Summary

Chapter 30  Sample Applets

• Hello Web!
• An Audio Player
• BlackJack Revisited
• Summary

Chapter 31  Developing Applets

• How Applets Work
  • The Relationship Between HTML and Applets
  • Applets and Interactive Web Pages
  • Applets Versus Scripts
  • The Execution of an Applet
  • Using Window Components
  • Adding Content and Protocol Handlers to Applets
• Using Applets as Inline Viewers
• Using Applets as Network Clients
• Optimizing Applets
• Learning from Online Examples
• Summary

Chapter 32  Integrating Applets into Distributed Applications

• Architecture for Distributed Applications
• OMG and CORBA
  • The Spring Project and Java IDL
  • NEO and JOE
  • JIDL
  • Black Widow
  • HORB
• Interfacing with CGI Programs
  • How CGI Programs Work
• Connecting Applets with CGI Programs
  • Fortune Teller
• Summary

Chapter 33  Working with JavaScript

• JavaScript and Java
• How JavaScript Works
• The Relationship Between HTML and Scripts
• Embedding JavaScript
• Combining Scripts with Applets
• Summary

Chapter 34  Sample Scripts

• A Customizable Web Page
• Story Teller
• Web Guide
• Summary

Chapter 35  JavaScript Reference

• JavaScript Objects
• Properties and Methods
  • The navigator Object
  • The window Object
  • The location Object
  • The history Object
  • The document Object
  • The form Object
  • The button Object
  • The checkbox Object
  • The text, textarea, hidden, and password Objects
  • The radio Object
  • The select Object
  • The string Object
  • The Date Object
  • The Math Object
• Handling Events
• Arrays
• Operators and Expressions
• Statements
• Summary

Chapter 36  The Java Source Code

• Obtaining the Java Source Code
• Platform Differences
• Platform Benchmarks
• Windows 95/NT Overview
• Summary

Chapter 37  The Java Virtual Machine

• Overview
• Structure of .class Files
  • Magic
  • Version
  • Constant_pool
  • Access_flags
  • This_class
  • Interfaces
  • Fields
  • Methods
  • Attributes
• Virtual Machine Architecture
  • JVM Registers
  • JVM Stack
  • Garbage-Collected Heap
  • Method Area
• Instruction Set
  • Pushing Constants onto the Stack
  • Pushing Local Variables onto the Stack
  • Storing Stack Values into Local Variables
  • Managing Arrays
  • Stack Instructions
  • Arithmetic Instructions
  • Logical Instructions
  • Conversion Operations
  • Control Transfer Instructions
  • Function Return Instructions
  • Table Jumping Instructions
  • Manipulating Object Fields
  • Method Invocation
  • Exception Handling
  • Object Utility Operations
  • Monitors
  • The breakpoint Instruction
• Summary

Chapter 38  Creating Native Methods

• Using Native Methods
• How Native Methods Are Called
• How Native Methods Are Created
• Summary

Chapter 39  Java Security

• Threats to Java Security
• Java Security Features
  • Language Security Features
  • Compiler Security Features
  • Runtime Security Mechanisms
• Staying Current with Java Security Issues
• Summary

Chapter 40  Java Platforms and Extensions

• Java-Enabled Browsers
  • HotJava
  • Netscape Navigator
  • Oracle PowerBrowser
• Borland's Latte
  • Visual Design
  • The Integrated Development Environment
  • Performance Improvements
• Symantec's Café
• Database Extensions
• VRML Extensions with Iced Java/Liquid Reality
  • Three-Dimensional Modeling
  • Iced Java and Liquid Reality
• Summary

Appendix A  The Jawa API Quick Reference

• java.applet
• java.awt
• java.awt.image
• java.awt.peer
• java.io
• java.lang
• java.net
• java.util

Appendix B  Differences Between java and C++

• Program Structure
  • The main() Method
  • Packages
  • Importing Classes
  • Functions and Variables Declared Outside of Classes
• Program Development
• Compilation and Execution
• The Preprocessor and Compiler Directives
• The Java API Versus C++ Libraries
• Using CLASSPATH
• Language Syntax
  • Comments
  • Constants
  • Primitive Data Types
  • Keywords
  • Java Classes Versus C++ Classes
  • Public, Private, and Protected Keywords
  • Variables
  • Types
  • Pointers
  • Objects
  • Arrays
  • Strings
  • null Versus NULL
  • Statements
  • Methods Versus Functions
  • Operators

Appendix C  Moving C/C++ Legacy Code to Java

• Why Move to Java?
  • Platform Independence
  • Object Orientation
  • Security
  • Reliability
  • Simplicity
  • Language Features
  • Standardization
  • The Java API
  • Transition to Distributed Computing
  • Rapid Code Generation
  • Ease of Documentation and Maintenance
• Reasons Against Moving to Java
  • Compatibility
  • Performance
  • Retraining
  • Impact on Existing Operations
  • Cost, Schedule, and Level of Effort
• Transition Approaches and Issues
  • Interfacing with Existing Legacy Cod
  • Incremental Reimplementation of Legacy Code
  • Off-Boarding Access to Legacy Objects
  • Full-Scale Redevelopment
• Translation Approaches and Issues
  • Automated Translation
  • Manual Translation
  • Source-Level Redesign

Credits

Copyright © 1996 by Jamie Jaworski

FIRST EDITION

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Trademarks

All terms mentioned in this book that are known to be trademarks or service marks have been appropriately capitalized. Sams.net Publishing cannot attest to the accuracy of this information. Use of a term in this book should not be regarded as affecting the validity of any trademark or service mark. Java is a trademark of Sun Microsystems, Inc.

Acknowledgments

I'd like to thank everyone who helped to see this book to completion. In particular, I'd like to thank George Stones for introducing me to Java, Margo Maley for making the book possible, and everyone at Sams.net for their great support. I'd also like to thank my co-author, Cary Jardin, for helping me finish the book closer to the scheduled deadline.

About the Author

James Jaworski develops advanced systems for the United States Department of Defense. He has used Java in several research and development projects, including a terrain analysis program and a genetic algorithm demonstration.

Introduction

Never before has a new programming language received so much attention and become so popular so quickly. In less than a year, Java evolved from experimental Alpha and Beta versions to its initial 1.0 release. Along the way, it took the Web by storm and became its adopted programming language. The Java phenomenon has captivated the imaginations of Web programmers and content developers and is leading the way toward the next era of Internet application development.

Java's appeal lies in its simplicity, its familiarity, and the careful selection of programming features that it includes and excludes. Java was not designed by a government committee or by a clique of academics. It shares the spirit of its birth with C more than any syntactical similarities. It is a programming language that was designed by programmers for programmers.

This book shows you how to program in Java. It covers all the details of the language, provides you with plenty of programming examples, and most importantly, arms you with the mindset needed to write Java code in a manner that is simple, efficient, and true to the nature of the language.

Who Should Read This Book

If you want someone to teach you how to program in Java, this book is for you. You will learn how to develop standalone Java programs, Java applets, and JavaScript applets. You will learn how to program window GUI controls, work with network sockets, and use stream-based input and output. You will learn to develop object-oriented programs and explore the breadth and depth of the Java application program interface. If you want to become a Java programmer, this book will show you how.

This book is for programmers and those who aspire to become Java programmers. It consists of 40 chapters that are filled with programming examples. If you have written programs in other languages, you will have the necessary background to understand the material presented in this book. If you have programmed in C or C++, then you will be able to quickly get up to speed with Java, since its syntax is based on these languages. If you have never programmed before, then you will have a difficult time using this book, because it assumes familiarity with basic programming concepts such as variables, types, statements, and expressions. I suggest that you pick up an introductory programming book to help you learn this material.

Conventions Used in This Book

This book uses certain conventions that make it easier for you to use.

A monospaced font is used to identify program code. An italic monospaced font is used to identify placeholders used in Java syntax descriptions.

In order to help you understand where you are going and where you have been, each chapter begins with a short description of the information that will be presented and ends with a summary of the material that has been covered.

Getting Started

To use this book with the Java Developer's Kit, you'll need a computer and operating system that are capable of running Java 1.0. There are a wide variety of computers and operating systems that support Java, and Java continues to be ported to new hardware and software platforms.

To effectively use Java with Windows 95, you will need the following:

• A personal computer that is capable of running Windows 95
• At least 8MB of RAM
• At least 10MB of available hard disk space
• A VGA monitor
• A mouse

To effectively use this book, you will need access to a compact disc drive so that you can copy files from the enclosed CD. In addition, an Internet connection will be required to complete some of the networking examples, and a Java-enabled browser, such as Netscape 2.0 or later, will be needed to work with Java applets and JavaScript. A sound card and speakers will be needed to use audio-playing applets.

You can get started if you are able to run Windows 95 and have access to the Web. Chapter 2 shows you how to obtain the Java Developer's Kit from Sun's JavaSoft website. You can add additional hardware, as necessary, to complete the programming examples of each chapter.

The best way to use this book is to start with Chapter 1 and proceed through each chapter, in succession, working through each programming example that is presented. You will learn to program in Java by compiling, running, analyzing, and understanding the sample programs. Additional hands-on learning can be acquired by tinkering with the sample programs, modifying them, and augmenting their capabilities.