Java Design Patterns A tutorial 2000.pdf

Java™ Design Patterns: A Tutorial

Publisher : Addison Wesley

Pub Date : January 28, 2000

ISBN : 0-201-48539-7

Pages : 352

Design patterns have become a staple of object-oriented design and programming by

providing elegant, easy-to-reuse, and maintainable solutions to commonly encountered

programming challenges. However, many busy Java programmers have yet to learn about

design patterns and incorporate this powerful technology into their work.

Java(TM)Design Patterns is exactly the tutorial resource you need. Gentle and clearly

written, it helps you understand the nature and purpose of design patterns. It also serves

as a practical guide to using design patterns to create sophisticated, robust Java programs.

This book presents the 23 patterns cataloged in the flagship book Design Patterns by

Gamma, Helm, Johnson, and Vlissides. In Java(TM)Design Patterns, each of these

patterns is illustrated by at least one complete visual Java program. This practical

approach makes design pattern concepts more concrete and easier to grasp, brings Java

programmers up to speed quickly, and enables you to take practical advantage of the

power of design patterns.

Key features include:

• Introductory overviews of design patterns, the Java Foundation Classes (JFC),

and the Unified Modeling Language (UML)

• Screen shots of each of the programs

• UML diagrams illustrating interactions between the classes, along with the

original JVISION diagram files

• An explanation of the Java Foundation Classes that illustrates numerous design

patterns

• Case studies demonstrating the usefulness of design patterns in solving Java

programming problems

• A CD containing all of the examples in the book, so you can run, edit, and

modify the complete working programs

After reading this tutorial, you will be comfortable with the basics of design patterns and

will be able to start using them effectively in your day-to-day Java programming work.

Team-Fly ®

By James W. Cooper

Table of Content

Table of Content ...........................................................................................................i

Copyright .............................................................................................................. viii

Credits ..................................................................................................................ix

Preface .....................................................................................................................ix

About the Author ......................................................................................................x

Acknowledgments ...................................................................................................x

Section 1: What Are Design Patterns? ..................................................................12

Chapter 1. Introduction .........................................................................................13

Defining Design Patterns .................................................................................14

The Learning Process ......................................................................................15

Studying Design Patterns ................................................................................16

Notes on Object-Oriented Approaches ..........................................................16

The Java Foundation Classes .........................................................................17

Java Design Patterns ........................................................................................17

Chapter 2. UML Diagrams ...................................................................................18

Inheritance ..........................................................................................................19

Interfaces ............................................................................................................20

Composition .......................................................................................................20

Annotation ..........................................................................................................22

JVISION UML Diagrams ..................................................................................22

Visual SlickEdit Project Files ...........................................................................22

Section 2: Creational Patterns ................................................................................24

Chapter 3. The Factory Pattern ..........................................................................25

How a Factory Works .......................................................................................25

Sample Code .....................................................................................................25

The Two Subclasses ........................................................................................26

Building the Simple Factory .............................................................................27

Factory Patterns in Math Computation ..........................................................28

Programs on the CD-ROM ..............................................................................29

Chapter 4. The Factory Method ..........................................................................30

The Swimmer Class ..........................................................................................32

The Event Classes ............................................................................................32

Straight Seeding ................................................................................................33

Our Seeding Program .......................................................................................35

Other Factories ..................................................................................................35

When to Use a Factory Method ......................................................................35

Programs on the CD-ROM ..............................................................................36

Chapter 5. The Abstract Factory Pattern ...........................................................37

A GardenMaker Factory ...................................................................................37

How the User Interface Works ........................................................................39

Adding More Classes ........................................................................................40

Consequences of the Abstract Factory Pattern ...........................................41

Programs on the CD-ROM ..............................................................................41

Chapter 6. The Singleton pattern ........................................................................42

Creating a Singleton Using a Static Method .................................................42

Exceptions and Instances ................................................................................43

Throwing an Exception .....................................................................................43

Creating an Instance of the Class ..................................................................43

Providing a Global Point of Access to a Singleton Pattern .........................44

The javax.comm Package as a Singleton .....................................................45

Other Consequences of the Singleton Pattern .............................................48

Programs on the CD-ROM ..............................................................................48

Chapter 7. The Builder Pattern ...........................................................................50

An Investment Tracker .....................................................................................50

Calling the Builders ...........................................................................................52

The List Box Builder ..........................................................................................54

The Check Box Builder .....................................................................................54

Consequences of the Builder Pattern ............................................................56

Programs on the CD-ROM ..............................................................................57

Chapter 8. The Prototype Pattern .......................................................................58

Cloning in Java ..................................................................................................58

Using the Prototype ..........................................................................................59

Using the Prototype Pattern ............................................................................62

Prototype Managers ..........................................................................................65

Cloning Using Serialization ..............................................................................65

Consequences of the Prototype Pattern ........................................................66

Programs on the CD-ROM ..............................................................................67

Summary of Creational Patterns .....................................................................68

Section 3: Structural Patterns ..................................................................................69

Chapter 9. The Adapter Pattern ..........................................................................70

Moving Data between Lists ..............................................................................70

Using the JFC JList Class ................................................................................71

Two-Way Adapters ............................................................................................76

Pluggable Adapters ...........................................................................................76

Adapters in Java ................................................................................................77

Programs on the CD-ROM ..............................................................................78

Chapter 10. The Bridge Pattern ..........................................................................80

The Class Diagram ...........................................................................................81

Extending the Bridge ........................................................................................82

Java Beans as Bridges .....................................................................................84

Consequences of the Bridge Pattern .............................................................85

Programs on the CD-ROM ..............................................................................85

Chapter 11. The Composite Pattern ..................................................................87

An Implementation of a Composite ................................................................87

Computing Salaries ...........................................................................................88

The Employee Classes ....................................................................................88

The Boss Class ..................................................................................................90

Building the Employee Tree ............................................................................91

Self-Promotion ...................................................................................................93

Doubly Linked List .............................................................................................94

Consequences of the Composite Pattern ......................................................95

A Simple Composite .........................................................................................95

Composites in Java ...........................................................................................96

Other Implementation Issues ..........................................................................96

Programs on the CD-ROM ..............................................................................96

Chapter 12. The Decorator Pattern ....................................................................98

Decorating a CoolButton ..................................................................................98

iii

Using a Decorator .............................................................................................99

The Class Diagram .........................................................................................101

Decorating Borders in Java ...........................................................................101

Nonvisual Decorators .....................................................................................103

Decorators, Adapters, and Composites .......................................................105

Consequences of the Decorator Pattern .....................................................106

Programs on the CD-ROM ............................................................................106

Chapter 13. The Façade Pattern ......................................................................107

Building the Façade Classes .........................................................................108

Consequences of the Façade Pattern .........................................................112

Notes on Installing and Running the dbFrame Program ...........................112

Programs on the CD-ROM ............................................................................113

Chapter 14. The Flyweight Pattern ...................................................................114

Discussion ........................................................................................................115

Example Code .................................................................................................115

Flyweight Uses in Java ...................................................................................119

Sharable Objects .............................................................................................120

Copy-on-Write Objects ...................................................................................120

Programs on the CD-ROM ............................................................................120

Chapter 15. The Proxy Pattern .........................................................................122

Sample Code ...................................................................................................122

Copy-on-Write ..................................................................................................124

Enterprise Java Beans ...................................................................................124

Comparison with Related Patterns ...............................................................125

Programs on the CD-ROM ............................................................................125

Summary of Structural Patterns ....................................................................126

Section 4: Behavioral Patterns ..............................................................................127

Chapter 16. Chain of Responsibility Pattern ...................................................128

Applicability ......................................................................................................129

Sample Code ...................................................................................................129

The List Boxes .................................................................................................132

Programming a Help System ........................................................................134

A Chain or a Tree? ..........................................................................................137

Kinds of Requests ...........................................................................................139

Examples in Java ............................................................................................139

Consequences of the Chain of Responsibility ............................................139

Programs on the CD-ROM ............................................................................140

Chapter 17. The Command Pattern .................................................................141

Motivation .........................................................................................................141

Command Objects ..........................................................................................142

Building Command Objects ...........................................................................143

The Command Pattern ...................................................................................144

The Command Pattern in the Java Language ............................................147

Consequences of the Command Pattern ....................................................147

Providing Undo ................................................................................................148

Programs on the CD-ROM ............................................................................152

Chapter 18. The Interpreter Pattern .................................................................153

Motivation .........................................................................................................153

Applicability ......................................................................................................153

Simple Report Example ..................................................................................153

Interpreting the Language ..............................................................................154

Objects Used in Parsing .................................................................................155

Reducing the Parsed Stack ...........................................................................158

Implementing the Interpreter Pattern ...........................................................159

Consequences of the Interpreter Pattern ....................................................163

Programs on the CD-ROM ............................................................................164

Chapter 19. The Iterator Pattern .......................................................................165

Motivation .........................................................................................................165

Enumerations in Java .....................................................................................165

Sample Code ...................................................................................................166

Filtered Iterators ..............................................................................................167

Consequences of the Iterator Pattern ..........................................................169

Composites and Iterators ...............................................................................170

Iterators in Java 1.2 ........................................................................................170

Programs on the CD-ROM ............................................................................171

Chapter 20. The Mediator Pattern ....................................................................172

An Example System ........................................................................................172

Interactions between Controls .......................................................................173

Sample Code ...................................................................................................174

Mediators and Command Objects ................................................................177

Consequences of the Mediator Pattern .......................................................178

Single Interface Mediators .............................................................................178

Implementation Issues ....................................................................................178

Programs on the CD-ROM ............................................................................179

Chapter 21. The Memento Pattern ...................................................................180

Motivation .........................................................................................................180

Implementation ................................................................................................180

Sample Code ...................................................................................................181

Consequences of the Memento Pattern ......................................................187

Programs on the CD-ROM ............................................................................187

Chapter 22. The Observer Pattern ...................................................................189

Watching Colors Change ...............................................................................190

The Message to the Media ............................................................................193

The JList as an Observer ...............................................................................193

The MVC Architecture as an Observer ........................................................195

The Observer Interface and Observable Class ..........................................195

Consequences of the Observer Pattern ......................................................196

Programs on the CD-ROM ............................................................................196

Chapter 23. The State Pattern ..........................................................................197

Sample Code ...................................................................................................197

Switching between States ..............................................................................201

How the Mediator Interacts with the StateManager ...................................201

State Transitions ..............................................................................................204

Mediators and the God Class ........................................................................204

Consequences of the State Pattern .............................................................205

Programs on the CD-ROM ............................................................................205

Chapter 24. The Strategy Pattern .....................................................................206

Motivation .........................................................................................................206

Sample Code ...................................................................................................206

The Context Class ...........................................................................................208

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