Summary of Part I

We've covered a lot of material so far! The following "concurrency cheat sheet" summarizes the main concepts and rules presented in Part I.

  • It's the mutable state, stupid. [1]

    All concurrency issues boil down to coordinating access to mutable state. The less mutable state, the easier it is to ensure thread safety.

  • Make fields final unless they need to be mutable.
  • Immutable objects are automatically thread-safe.

    Immutable objects simplify concurrent programming tremendously. They are simpler and safer, and can be shared freely without locking or defensive copying.

  • Encapsulation makes it practical to manage the complexity.

    You could write a thread-safe program with all data stored in global variables, but why would you want to? Encapsulating data within objects makes it easier to preserve their invariants; encapsulating synchronization within objects makes it easier to comply with their synchronization policy.

  • Guard each mutable variable with a lock.
  • Guard all variables in an invariant with the same lock.
  • Hold locks for the duration of compound actions.
  • A program that accesses a mutable variable from multiple threads without synchronization is a broken program.
  • Don't rely on clever reasoning about why you don't need to synchronize.
  • Include thread safety in the design processor explicitly document that your class is not thread-safe.
  • Document your synchronization policy.

[1] During the 1992 U.S. presidential election, electoral strategist James Carville hung a sign in Bill Clinton's campaign headquarters reading "The economy, stupid", to keep the campaign on message.


Introduction

Part I: Fundamentals

Thread Safety

Sharing Objects

Composing Objects

Building Blocks

Part II: Structuring Concurrent Applications

Task Execution

Cancellation and Shutdown

Applying Thread Pools

GUI Applications

Part III: Liveness, Performance, and Testing

Avoiding Liveness Hazards

Performance and Scalability

Testing Concurrent Programs

Part IV: Advanced Topics

Explicit Locks

Building Custom Synchronizers

Atomic Variables and Nonblocking Synchronization

The Java Memory Model

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Java Concurrency in Practice
Java Concurrency in Practice
ISBN: 0321349601
EAN: 2147483647
Year: 2004
Pages: 141
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