Implementation Patterns

by Beck, Kent

• ISBN13: 9780321413093
• ISBN10: 0321413091
• Edition: 1st
• Format: Paperback
• Copyright: 2007-10-23
• Publisher: Addison-Wesley Professional

Summary

"Kent is a master at creating code that communicates well, is easy to understand, and is a pleasure to read. Every chapter of this book contains excellent explanations and insights into the smaller but important decisions we continuously have to make when creating quality code and classes." Erich Gamma, IBM Distinguished Engineer "Many teams have a master developer who makes a rapid stream of good decisions all day long. Their code is easy to understand, quick to modify, and feels safe and comfortable to work with. If you ask how they thought to write something the way they did, they always have a good reason. This book will help you become the master developer on your team. The breadth and depth of topics will engage veteran programmers, who will pick up new tricks and improve on old habits, while the clarity makes it accessible to even novice developers." Russ Rufer, Silicon Valley Patterns Group "Many people donrs"t realize how readable code can be and how valuable that readability is. Kent has taught me so much, Irs"m glad this book gives everyone the chance to learn from him." Martin Fowler, chief scientist, ThoughtWorks "Code should be worth reading, not just by the compiler, but by humans. Kent Beck distilled his experience into a cohesive collection of implementation patterns. These nuggets of advice will make your code truly worth reading." Gregor Hohpe, author ofEnterprise Integration Patterns "In this book Kent Beck shows how writing clear and readable code follows from the application of simple principles.Implementation Patternswill help developers write intention revealing code that is both easy to understand and flexible towards future extensions. A must read for developers who are serious about their code." Sven Gorts "Implementation Patternsbridges the gap between design and coding. Beck introduces a new way of thinking about programming by basing his discussion on values and principles." Diomidis Spinellis, author ofCode ReadingandCode Quality Software Expert Kent Beck Presents a Catalog of Patterns Infinitely Useful for Everyday Programming Great code doesnrs"t just function: it clearly and consistently communicates your intentions, allowing other programmers to understand your code, rely on it, and modify it with confidence. But great code doesnrs"t just happen. It is the outcome of hundreds of small but critical decisions programmers make every single day. Now, legendary software innovator Kent Beckknown worldwide for creating Extreme Programming and pioneering software patterns and test-driven developmentfocuses on these critical decisions, unearthing powerful "implementation patterns" for writing programs that are simpler, clearer, better organized, and more cost effective. Beck collects 77 patterns for handling everyday programming tasks and writing more readable code. This new collection of patterns addresses many aspects of development, including class, state, behavior, method, collections, frameworks, and more. He uses diagrams, stories, examples, and essays to engage the reader as he illuminates the patterns. You

Author Biography

Kent Beck, one of the software industry’s most creative and acclaimed leaders, consistently challenges software engineering dogma and promotes ideas like patterns, test-driven development, and Extreme Programming. Currently affiliated with Three Rivers Institute and Agitar Software, he is the author of many Addison-Wesley titles, including Test-Driven Development (2003) and, with Cynthia Andres, Extreme Programming Explained, Second Edition (2005).

Table of Contents

Preface	p. xv
Acknowledgments	p. xvi
Introduction	p. 1
Tour Guide	p. 3
And Now...	p. 4
Patterns	p. 5
A Theory of Programming	p. 9
Values	p. 10
Communication	p. 10
Simplicity	p. 11
Flexibility	p. 12
Principles	p. 13
Local Consequences	p. 13
Minimize Repetition	p. 14
Logic and Data Together	p. 14
Symmetry	p. 15
Declarative Expression	p. 16
Rate of Change	p. 17
Conclusion	p. 18
Motivation	p. 19
Class	p. 21
Class	p. 22
Simple Superclass Name	p. 23
Qualified Subclass Name	p. 24
Abstract Interface	p. 24
Interface	p. 26
Abstract Class	p. 26
Versioned Interface	p. 27
Value Object	p. 28
Specialization	p. 31
Subclass	p. 32
Implementor	p. 34
Inner Class	p. 34
Instance-Specific Behavior	p. 36
Conditional	p. 36
Delegation	p. 38
Pluggable Selector	p. 40
Anonymous Inner Class	p. 41
Library Class	p. 41
Conclusion	p. 42
State	p. 43
State	p. 44
Access	p. 45
Direct Access	p. 46
Indirect Access	p. 47
Common State	p. 47
Variable State	p. 48
Extrinsic State	p. 50
Variable	p. 50
Local Variable	p. 51
Field	p. 52
Parameter	p. 53
Collecting Parameter	p. 55
Optional Parameter	p. 56
Var Args	p. 56
Parameter Object	p. 57
Constant	p. 58
Role-Suggesting Name	p. 58
Declared Type	p. 60
Initialization	p. 61
Eager Initialization	p. 61
Lazy Initialization	p. 62
Conclusion	p. 62
Behavior	p. 63
Control Flow	p. 64
Main Flow	p. 64
Message	p. 65
Choosing Message	p. 65
Double Dispatch	p. 66
Decomposing (Sequencing) Message	p. 67
Reversing Message	p. 67
Inviting Message	p. 68
Explaining Message	p. 69
Exceptional Flow	p. 70
Guard Clause	p. 70
Exception	p. 72
Checked Exceptions	p. 72
Exception Propagation	p. 73
Conclusion	p. 73
Methods	p. 75
Composed Method	p. 77
Intention-Revealing Name	p. 79
Method Visibility	p. 80
Method Object	p. 82
Overridden Method	p. 83
Overloaded Method	p. 83
Method Return Type	p. 84
Method Comment	p. 85
Helper Method	p. 85
Debug Print Method	p. 86
Conversion	p. 87
Conversion Method	p. 87
Conversion Constructor	p. 88
Creation	p. 88
Complete Constructor	p. 89
Factory Method	p. 90
Internal Factory	p. 91
Collection Accessor Method	p. 91
Boolean Setting Method	p. 93
Query Method	p. 93
Equality Method	p. 94
Getting Method	p. 95
Setting Method	p. 96
Safe Copy	p. 97
Conclusion	p. 98
Collections	p. 99
Metaphors	p. 100
Issues	p. 101
Interfaces	p. 103
Array	p. 103
Iterable	p. 104
Collection	p. 104
List	p. 104
Set	p. 105
SortedSet	p. 105
Map	p. 106
Implementations	p. 107
Collection	p. 108
List	p. 108
Set	p. 108
Map	p. 109
Collections	p. 110
Searching	p. 111
Sorting	p. 112
Unmodifiable Collections	p. 113
Single-Element Collections	p. 114
Empty Collections	p. 114
Extending Collections	p. 114
Conclusion	p. 115
Evolving Frameworks	p. 117
Changing Frameworks without Changing Applications	p. 117
Incompatible Upgrades	p. 118
Encouraging Compatible Change	p. 120
Library Class	p. 121
Objects	p. 121
Conclusion	p. 129
Performance Measurement	p. 131
Example	p. 131
API	p. 132
Implementation	p. 133
MethodTimer	p. 134
Canceling Overhead	p. 136
Tests	p. 136
Comparing Collections	p. 137
Comparing ArrayList and LinkedList	p. 139
Comparing Sets	p. 140
Comparing Maps	p. 141
Conclusion	p. 142
Bibliography	p. 145
General Programming	p. 145
Philosophy	p. 147
Java	p. 148
Index	p. 149
Table of Contents provided by Ingram. All Rights Reserved.

Excerpts

This is a book about programmingspecifically, about programming so other people can understand your code. There is no magic to writing code other people can read. It's like all writingknow your audience, have a clear overall structure in mind, express the details so they contribute to the whole story. Java offers some good ways to communicate. The implementation patterns here are Java programming habits that result in readable code. Another way to look at implementation patterns is as a way of thinking "What do I want to tell a reader about this code?" Programmers spend so much of their time in their own heads that trying to look at the world from someone else's viewpoint is a big shift. Not just "What will the computer do with this code?" but "How can I communicate what I am thinking to people?" This shift in perspective is healthy and potentially profitable, since so much software development money is spent on understanding existing code. There is an American game show called Jeopardy in which the host supplies answers and the contestants try to guess the questions. "A word describing being thrown through a window." "What is 'defenestration'?" "Correct." Coding is like Jeopardy. Java provides answers in the form of its basic constructs. Programmers usually have to figure out for themselves what the questions are, what problems are solved by each language construct. If the answer is "Declare a field as a Set ." the question might be "How can I tell other programmers that a collection contains no duplicates?" The implementation patterns provide a catalog of the common problems in programming and the features of Java that address those problems. Scope management is as important in book writing as it is in software development. Here are some things this book is not. It is not a style guide because it contains too much explanation and leaves the final decisions up to the reader. It is not a design book because it is mostly concerned with smaller-scale decisions, the kind programmers make many times a day. It's not a patterns book because the format of the patterns is idiosyncratic andad hoc(literally "built for a particular purpose"). It's not a language book because, while it covers many Java language features, it assumes readers already know Java. Actually this book is built on a rather fragile premise: that good code matters. I have seen too much ugly code make too much money to believe that quality of code is either necessary or sufficient for commercial success or widespread use. However, I still believe that quality of code matters even if it doesn't provide control over the future. Businesses that are able to develop and release with confidence, shift direction in response to opportunities and competition, and maintain positive morale through challenges and setbacks will tend to be more successful than businesses with shoddy, buggy code. Even if there was no long-term economic impact from careful coding I would still choose to write the best code I could. A seventy-year lifespan contains just over two billion seconds. That's not enough seconds to waste on work I'm not proud of. Coding well is satisfying, both the act itself and the knowledge that others will be able to understand, appreciate, use, and extend my work. In the end, then, this is a book about responsibility. As a programmer you have been given time, talent, money, and opportunity. What will you do to make responsible use of these gifts? The pages that follow contain my answer to this question for me: code for others as well as myself and my buddy the CPU.