本书以作者自身学习、使用模式和多年来为软件开发人员（包括面向对象技术老兵和新手）讲授模式的经验为基础撰写而成。首先概述了模式的基础知识，以及面向对象分析和设计在当代软件开发中的重要性，随后使用易懂的示例代码阐明了12个最常用的模式，包括它们的基础概念、优点、权衡取舍、实现技术以及需要避免的缺陷，使读者能够理解模式背后的基本原则和动机，理解为什么它们会这样运作。

本书适合软件开发专业人士，以及计算机专业、软件工程专业的高校师生阅读，也可作为面向对象分析与设计课程的参考教材。

"One of the great things about the book is the way the authors explain concepts very simply using analogies rather than programming examples--this has been very inspiring for a product I'm working on: an audio-only introduction to OOP and software development." --Bruce Eckel "...I would expect that readers with a basic understanding of object-oriented programming and design would find this book useful, before approaching design patterns completely. Design Patterns Explained complements the existing design patterns texts and may perform a very useful role, fitting between introductory texts such as UML Distilled and the more advanced patterns books." --James Noble Leverage the quality and productivity benefits of patterns--without the complexity! Design Patterns Explained, Second Edition is the field's simplest, clearest, most practical introduction to patterns. Using dozens of updated Java examples, it shows programmers and architects exactly how to use patterns to design, develop, and deliver software far more effectively. You'll start with a complete overview of the fundamental principles of patterns, and the role of object-oriented analysis and design in contemporary software development. Then, using easy-to-understand sample code, Alan Shalloway and James Trott illuminate dozens of today's most useful patterns: their underlying concepts, advantages, tradeoffs, implementation techniques, and pitfalls to avoid. Many patterns are accompanied by UML diagrams. Building on their best-selling First Edition, Shalloway and Trott have thoroughly updated this book to reflect new software design trends, patterns, and implementation techniques. Reflecting extensive reader feedback, they have deepened and clarified coverage throughout, and reorganized content for even greater ease of understanding. New and revamped coverage in this edition includes * Better ways to start "thinking in patterns" * How design patterns can facilitate agile development using eXtreme Programming and other methods * How to use commonality and variability analysis to design application architectures * The key role of testing into a patterns-driven development process * How to use factories to instantiate and manage objects more effectively * The Object-Pool Pattern--a new pattern not identified by the "Gang of Four" * New study/practice questions at the end of every chapter Gentle yet thorough, this book assumes no patterns experience whatsoever. It's the ideal "first book" on patterns, and a perfect complement to Gamma's classic Design Patterns. If you're a programmer or architect who wants the clearest possible understanding of design patterns--or if you've struggled to make them work for you--read this book.