ritten for the working Java developer, Joshua Bloch's Effective Java
Programming Language Guide provides a truly useful set of over 50 best
practices and tips for writing better Java code. With plenty of advice
from an indisputable expert in the field, this title is sure to be an
indispensable resource for anyone who wants to get more out of their
code.

As a veteran developer at Sun, the author shares his considerable
insight into the design choices made over the years in Sun's own Java
libraries (which the author acknowledges haven't always been perfect).
Based on his experience working with Sun's best minds, the author
provides a compilation of 57 tips for better Java code organized by
category. Many of these ideas will let you write more robust classes
that better cooperate with built-in Java APIs. Many of the tips make use
of software patterns and demonstrate an up-to-the-minute sense of what
works best in today's design. Each tip is clearly introduced and
explained with code snippets used to demonstrate each programming
principle.

Early sections on creating and destroying objects show you ways to make
better use of resources, including how to avoid duplicate objects. Next
comes an absolutely indispensable guide to implementing "required"
methods for custom classes. This material will help you write new
classes that cooperate with old ones (with advice on implementing
essential requirements like the equals() and hashCode() methods).

The author has a lot to say about class design, whether using
inheritance or composition. Tips on designing methods show you how to
create understandable, maintainable, and robust classes that can be
easily reused by others on your team. Sections on mapping C code (like
structures, unions, and enumerated types) onto Java will help C
programmers bring their existing skills to Sun's new language. Later
sections delve into some general programming tips, like using exceptions
effectively. The book closes with advice on using threads and
synchronization techniques, plus some worthwhile advice on object
serialization.

Whatever your level of Java knowledge, this title can make you a more
effective programmer. Wisely written, yet never pompous or doctrinaire,
the author has succeeded in packaging some really valuable nuggets of
advice into a concise and very accessible guidebook that arguably
deserves a place on most any developer's bookshelf. --Richard Dragan

Topics covered:

* Best practices and tips for Java
* Creating and destroying objects (static factory methods,
singletons, avoiding duplicate objects and finalizers)
* Required methods for custom classes (overriding equals(),
hashCode(), toString(), clone(), and compareTo() properly)
* Hints for class and interface design (minimizing class and member
accessibility, immutability, composition versus inheritance, interfaces
versus abstract classes, preventing subclassing, static versus nonstatic
classes)
* C constructs in Java (structures, unions, enumerated types, and
function pointers in Java)
* Tips for designing methods (parameter validation, defensive
copies, method signatures, method overloading, zero-length arrays, hints
for Javadoc comments)
* General programming advice (local variable scope, using Java API
libraries, avoiding float and double for exact comparisons, when to
avoid strings, string concatenation, interfaces and reflection, avoid
native methods, optimizing hints, naming conventions)
* Programming with exceptions (checked versus run-time exceptions,
standard exceptions, documenting exceptions, failure-capture
information, failure atomicity)
* Threading and multitasking (synchronization and scheduling hints,
thread safety, avoiding thread groups)
* Serialization (when to implement Serializable, the readObject(),
and readResolve() methods)

table of contens:
CHAPTER = Foreword. Preface.
Acknowledgements.
1. Introduction.
2. Creating and Destroying Objects.
Consider Providing Static Factory Methods Instead of Constructors.
Enforce the Singleton Property with a Private Constructor.
Enforce Noninstantiability with a Private Constructor.
Avoid Creating Duplicate Objects.
Eliminate Obsolete Object References.
Avoid Finalizers.

3. Methods Common to All Objects.
Obey the General Contract when Overriding Equals.
Always Override HashCode When You Override Equals.
Always Override toString. Override Clone Judiciously.
Consider Implementing Comparable.

4. Classes and Interfaces.
Minimize the Accessibility of Classes and Members.
Favor Immutability. Favor Composition Over Inheritance.
Design and Document for Inheritance or Else Prohibit It.
Prefer Interfaces to Abstract Classes. Use Interfaces Only to Define
Types.
Favor Static Member Classes Over Non-Static.

5. Substitutes for C Constructs.
Replace Structures with Classes.
Replace Unions with Class Hierarchies.
Replace Enums with Classes.
Replace Function Pointers with Classes and Interfaces.

6. Methods.
Check Parameters for Validity.
Make Defensive Copies when Needed.
Design Method Signatures Carefully.
Use Overloading Judiciously.
Return Zero-Length Arrays, Not Nulls.
Write Doc Comments for All Exposed API Elements.

7. General Programming.
Minimize the Scope of Local Variables.
Know and Use the Libraries.
Avoid Float and Double if Exact Answers are Required.
Avoid Strings where Other Types are More Appropriate.
Beware the Performance of String Concatenation.
Refer to Objects by their Interfaces.
Prefer Interfaces to Reflection.
Use Native Methods Judiciously.
Optimize Judiciously.
Adhere to Generally Accepted Naming Conventions.

8. Exceptions.
Use Exceptions Only for Exceptional Conditions.
Use Checked Exceptions for Recoverable Conditions.
Runtime Exceptions for Programming Errors.
Avoid Unnecessary Use of Checked Exceptions.
Favor the Use of Standard Exceptions.
Throw Exceptions Appropriate to the Abstraction.
Document All Exceptions Thrown by Each Method.
Include Failure-Capture Information in Detail Messages.
Strive for Failure Atomicity.
Don't Ignore Exceptions.

9. Threads.
Synchronize Access to Shared Mutable Data.
Avoid Excessive Synchronization.
Never Invoke Wait Outside a Loop.
Don't Depend on the Thread Scheduler.
Document Thread-Safety.
Avoid Thread Groups.

10. Serialization.
Implement Serializable Judiciously.
Consider Using a Custom Serialized Form.
Write ReadObject Methods Defensively.
Provide a ReadResolve Method when Necessary.

References.
Index.

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