1 Introduction 1

11 WhatIs a Design Pattern? 2

1 2 Design Patterns in Smalltalk MVC 4

13 Describing Design Patterns 6

14 The Catalog of Design Patterns 8

15 Organizing the Catalog 9

16 How Design Patterns Solve Design Problems 11

17 Howto Selecta Design Pattern 28

18 Howto Use a Design Pattern 29 2 A Case Study: Designing a Document Editor 33 2 1 Design Problems 33 22 Document Structure 35 23 Formatting ~ 40 24 Embellishing the User Interface 43 25 Supporting Multiple Look-and-Feel Standards 47 26 Supporting Multiple Window Systems 51 27 User Operations 58 28 Spelling Checking and Hyphenation 64 29 Summary 76 Design Pattern Catalog 79 3 Creational Patterns 81 Abstract Factory 87 Builder 97 Factory Method 107 Prototype 117 Singleton 127 Discussion of Creational Patterns 135 4 Structural Patterns 137 Adapter 139 Bridge 151 Composite 163 Decorator 175 Facade 185 Flyweight 195 Proxy 207 Discussion of Structural Patterns 219 5 Behavioral Patterns 221 Chain of Responsibility 223 Command 233 Interpreter 243 Iterator 257 Mediator 273 Memento 283 Observer 293 State 305 Strate~v 315 Template Method 325 Visitor