Java Concurrency (java.util.concurrent)

The java.util.concurrent package (JSR-166) is a masterpiece of design by Doug Lea and others. It provides a standardized framework for asynchronous task execution, thread-safe collections, and advanced synchronization primitives.

This series explores the source code of the package to understand the engineering trade-offs and implementation details behind some of the most critical components of the JVM.

Table of Contents #

1. Executors: The core of Java’s task execution framework.

   • Executor, ExecutorService, AbstractExecutorService.
   • ThreadPoolExecutor and ScheduledThreadPoolExecutor.

2. Queues: Thread-safe data structures for producer-consumer patterns.

   • BlockingQueue Interface Overview.
   • ArrayBlockingQueue, LinkedBlockingQueue, SynchronousQueue.
   • LinkedTransferQueue and ConcurrentLinkedQueue.
   • Specialized Blocking Queues: DelayQueue and PriorityBlockingQueue.

3. Synchronizers: Advanced coordination primitives.

   • AbstractQueuedSynchronizer (AQS): The cornerstone of the framework.
   • Semaphore, CountDownLatch, CyclicBarrier.
   • Phaser and Exchanger.

4. Concurrent Collections: Scalable collections for multi-threaded environments.

   • ConcurrentMap and ConcurrentHashMap.
   • ConcurrentSkipListMap and CopyOnWriteArrayList.
   • Concurrent Sets: ConcurrentSkipListSet and CopyOnWriteArraySet.

5. Atomics and Locks: The foundation of wait-free and lock-free programming.

   • Atomic Variables and Advanced Atomics (AtomicReference, FieldUpdaters).
   • LongAdder and LockSupport.
   • ReentrantLock, ReentrantReadWriteLock, and StampedLock.

6. Modern & Advanced Concurrency: The future of Java threading.

   • ForkJoinPool and CompletableFuture.
   • Structured Concurrency (Loom).
   • Reactive Streams (Flow API).
   • Random and Helpers (ThreadLocalRandom, CompletionService).

This textbook is complete, covering all 60+ major classes in the java.util.concurrent package.