Table of Contents

Foreword xi

Preface xiii

Acknowledgments xvii

Chapter 1: Introduction 1

Chapter 2: Creating and Destroying Objects 5

Item 1: Consider static factory methods instead of constructors 5

Item 2: Consider a builder when faced with many constructor

parameters 11

Item 3: Enforce the singleton property with a private constructor 17

Item 4: Enforce noninstantiability with a private constructor 19

Item 5: Avoid creating unnecessary objects 20

Item 6: Eliminate obsolete object references 24

Item 7: Avoid finalizers 27

Chapter 3: Methods Common to All Objects 33

Item 8: Obey the general contract when overriding equals 33

Item 9: Always override hashCode when you override equals 45

Item 10: Always override toString 51

Item 11: Override clone judiciously 54

Item 12: Consider implementing Comparable 62

Chapter 4: Classes and Interfaces 67

Item 13: Minimize the accessibility of classes and members 67

Item 14: In public classes, use accessor methods, not public fields 71

Item 15: Minimize mutability 73

Item 16: Favor composition over inheritance 81

Item 17: Design and document for inheritance or else prohibit it 87

Item 18: Prefer interfaces to abstract classes 93

Item 19: Use interfaces only to define types 98

Item 20: Prefer class hierarchies to tagged classes 100

Item 21: Use function objects to represent strategies 103

Item 22: Favor static member classes over nonstatic 106

Chapter 5: Generics 109

Item 23: Don't use raw types in new code 109

Item 24: Eliminate unchecked warnings 116

Item 25: Prefer lists to arrays 119

Item 26: Favor generic types 124

Item 27: Favor generic methods 129

Item 28: Use bounded wildcards to increase API flexibility 134

Item 29: Consider typesafe heterogeneous containers 142

Chapter 6: Enums and Annotations 147

Item 30: Use enums instead of int constants 147

Item 31: Use instance fields instead of ordinals 158

Item 32: Use EnumSet instead of bit fields 159

Item 33: Use EnumMap instead of ordinal indexing 161

Item 34: Emulate extensible enums with interfaces 165

Item 35: Prefer annotations to naming patterns 169

Item 36: Consistently use the Override annotation 176

Item 37: Use marker interfaces to define types 179

Chapter 7: Methods 181

Item 38: Check parameters for validity 181

Item 39: Make defensive copies when needed 184

Item 40: Design method signatures carefully 189

Item 41: Use overloading judiciously 191

Item 42: Use varargs judiciously 197

Item 43: Return empty arrays or collections, not nulls 201

Item 44: Write doc comments for all exposed API elements 203

Chapter 8: General Programming 209

Item 45: Minimize the scope of local variables 209

Item 46: Prefer for-each loops to traditional for loops 212

Item 47: Know and use the libraries 215

Item 48: Avoid float and double if exact answers are required 218

Item 49: Prefer primitive types to boxed primitives 221

Item 50: Avoid strings where other types are more appropriate 224

Item 51: Beware the performance of string concatenation 227

Item 52: Refer to objects by their interfaces 228

Item 53: Prefer interfaces to reflection 230

Item 54: Use native methods judiciously 233

Item 55: Optimize judiciously 234

Item 56: Adhere to generally accepted naming conventions 237

Chapter 9: Exceptions 241

Item 57: Use exceptions only for exceptional conditions 241

Item 58: Use checked exceptions for recoverable conditions and runtime exceptions for programming errors 244

Item 59: Avoid unnecessary use of checked exceptions 246

Item 60: Favor the use of standard exceptions 248

Item 61: Throw exceptions appropriate to the abstraction 250

Item 62: Document all exceptions thrown by each method 252

Item 63: Include failure-capture information in detail messages 254

Item 64: Strive for failure atomicity 256

Item 65: Don’t ignore exceptions 258

Chapter 10: Concurrency 259

Item 66: Synchronize access to shared mutable data 259

Item 67: Avoid excessive synchronization 265

Item 68: Prefer executors and tasks to threads 271

Item 69: Prefer concurrency utilities to wait and notify 273

Item 70: Document thread safety 278

Item 71: Use lazy initialization judiciously 282

Item 72: Don’t depend on the thread scheduler 286

Item 73: Avoid thread groups 288

Chapter 11: Serialization 289

Item 74: Implement Serializable judiciously 289

Item 75: Consider using a custom serialized form 295

Item 76: Write readObject methods defensively 302

Item 77: For instance control, prefer enum types to readResolve 309

Item 78: Consider serialization proxies instead of serialized instances 313

Appendix: Items Corresponding to First Edition 317

References 321

Index of Patterns and Idioms 327

Index 331

Promotional Information

This book is designed to help Java programmers make the most effective use of the Java programming language and its fundamental libraries, java.lang, java.util, and java.io. There are over 50 items or essays, each of which conveys one rule. Each rule captures best practices that have been tested in the real world. Just one of the key features in this book are the code examples that illustrate many useful design patterns and idoms. Another key feature is the advice on what not to do. Providing examples of what practices to avoid helps programmers side step common misconceptions and errors. While the second edition will cover all of the classic topics developers have come to rely on- objects, classes, libraries, methods, and serialization; new to this edition will be the coverage on generics, metadata, autoboxing, concurrency utilities, memory model, enumerations, and more. The book is based on the philosophy that clarity and simplicity are of paramount importance. The concise essays teach Java programmers of all levels how to write correct, clear, reusable, and effective code. Learning the art of Java programming, like most other disciples, consists of learning the rules and then learning when to violate them. With this book in hand, Java programmers will truly learn the rules and then learn when to violate them.

About the Author

Joshua Bloch is chief Java architect at Google and a Jolt Award winner. He was previously a distinguished engineer at Sun Microsystems and a senior systems designer at Transarc. Bloch led the design and implementation of numerous Java platform features, including JDK 5.0 language enhancements and the award-winning Java Collections Framework. He coauthored Java Puzzlers (Addison-Wesley, 2005) and Java Concurrency in Practice (Addison-Wesley, 2006).

Reviews

Raves for the First Edition!

 

“I sure wish I had this book ten years ago. Some might think that I don’t need any Java books, but I need this one.”

—James Gosling, fellow and vice president, Sun Microsystems, Inc.

 

“An excellent book, crammed with good advice on using the Java programming language and object-oriented programming in general.”

—Gilad Bracha, coauthor of The Java™ Language Specification, Third Edition

 

“10/10—anyone aspiring to write good Java code that others will appreciate reading and maintaining should be required to own a copy of this book. This is one of those rare books where the information won’t become obsolete with subsequent releases of the JDK library.”
—Peter Tran, bartender, JavaRanch.com

 

“The best Java book yet written.... Really great; very readable and eminently useful. I can’t say enough good things about this book. At JavaOne 2001, James Gosling said, ‘Go buy this book!’ I’m glad I did, and I couldn’t agree more.”
—Keith Edwards, senior member of research staff, Computer Science Lab at the Palo Alto Research Center (PARC), and author of Core JINI (Prentice Hall, 2000)

 

“This is a truly excellent book done by the guy who designed several of the better recent Java platform APIs (including the Collections API).”
—James Clark, technical lead of the XML Working Group during the creation of the XML 1.0 Recommendation, editor of the XPath and XSLT Recommendations

 

“Great content. Analogous to Scott Meyers’ classic Effective C++. If you know the basics of Java, this has to be your next book.”
—Gary K. Evans, OO mentor and consultant, Evanetics, Inc

 

“Josh Bloch gives great insight into best practices that really can only be discovered after years of study and experience.”
—Mark Mascolino, software engineer

 

“This is a superb book. It clearly covers many of the language/platform subtleties and trickery you need to learn to become a real Java master.”
—Victor Wiewiorowski, vice president development and code quality manager, ValueCommerce Co., Tokyo, Japan

 

“I like books that under-promise in their titles and over-deliver in their contents. This book has 57 items of programming advice that are well chosen. Each item reveals a clear, deep grasp of the language. Each one illustrates in simple, practical terms the limits of programming on intuition alone, or taking the most direct path to a solution without fully understanding what the language offers.”

—Michael Ernest, Inkling Research, Inc.

 

“I don’t find many programming books that make me want to read every page—this is one of them.”
—Matt Tucker, chief technical officer, Jive Software

 

“Great how-to resource for the experienced developer.”
—John Zukowski, author of numerous Java technology books