Java Concurrency in Practice - Brian Goetz

As processors become faster and multiprocessor systems become cheaper, the need to take advantage of multithreading in order to achieve full hardware resource utilization only increases the importance of being able to incorporate concurrency in a wide variety of application categories. For many developers, concurrency remains a mystery. Developing, testing and debugging multithreaded programs is extremely difficult because concurrency hazards do not manifest themselves uniformly or reliably. This book is intended to be neither an introduction to concurrency (any threading chapter in an "intro" book does that) nor is it an encyclopedic reference of All Things Concurrency (that would be Doug Lea\'s Concurrent Programming in Java). Instead, this title is a combination of concepts, guidelines, and examples intended to assist developers in the difficult process of understanding concurrency and its new tools in J2SE 5.0. Filled with contributions from Java gurus such as Josh Bloch, David Holmes and Doug Lea, this book provides any Java programmers with the basic building blocks they need to gain a basic understanding of concurrency and its benefits.

Table of Contents

Listings xii

Preface xvii

Chapter 1: Introduction 1 1.1 A (very) brief history of concurrency 1 1.2 Benefits of threads 3 1.3 Risks of threads 5 1.4 Threads are everywhere 9

• Part I: Fundamentals 13
• Chapter 2: Thread Safety 15

2.1 What is thread safety? 17 2.2 Atomicity 19 2.3 Locking 23 2.4 Guarding state with locks 27 2.5 Liveness and performance 29

Chapter 3: Sharing Objects 33 3.1 Visibility 33 3.2 Publication and escape 39 3.3 Thread confinement 42 3.4 Immutability 46 3.5 Safepublication 49

Chapter 4: Composing Objects 55 4.1 Designing a thread-safe class 55 4.2 Instance confinement 58 4.3 Delegating thread safety 62 4.4 Adding functionality to existing thread-safe classes 71 4.5 Documenting synchronization policies 74

Chapter 5: Building Blocks 79 5.1 Synchronized collections 79 5.2 Concurrent collections 84 5.3 Blocking queues and the producer-consumer pattern 87 5.4 Blocking and interruptible methods 92 5.5 Synchronizers 94 5.6 Building an efficient, scalable result cache 101

• Part II: Structuring Concurrent Applications 111
• Chapter 6: Task Execution 113

6.1 Executing tasks in threads 113 6.2 The Executor framework 117 6.3 Finding exploitable parallelism 123

Chapter 7: Cancellation and Shutdown 135 7.1 Task cancellation 135 7.2 Stopping a thread-based service 150 7.3 Handling abnormal thread termination 161 7.4 JVM shutdown 164

Chapter 8: Applying Thread Pools 167 8.1 Implicit couplings between tasks and execution policies 167 8.2 Sizing thread pools 170 8.3 Configuring ThreadPoolExecutor 171 8.4 Extending ThreadPoolExecutor 179 8.5 Parallelizing recursive algorithms 181

Chapter 9: GUI Applications 189 9.1 Why are GUIs single-threaded? 189 9.2 Short-running GUI tasks 192 9.3 Long-running GUI tasks 195 9.4 Shared data models 198 9.5 Other forms of single-threaded subsystems 202

• Part III: Liveness, Performance, and Testing 203
• Chapter 10: Avoiding Liveness Hazards 205

10.1 Deadlock 205 10.2 Avoiding and diagnosing deadlocks 215 10.3 Other liveness hazards 218

Chapter 11: Performance and Scalability 221 11.1 Thinking about performance 221 11.2 Amdahl\'s law 225 11.3 Costs introduced by threads 229 11.4 Reducing lock contention 2