Comprehensive Guide to Java Concurrency: Threads, Locks, Executors, and Synchronization Primitives

This guide explores Java's concurrency model, starting with thread creation using Thread, Runnable, and Callable, and explains thread lifecycle states such as NEW, RUNNABLE, BLOCKED, WAITING, TIMED_WAITING, and TERMINATED.

It details synchronization primitives including intrinsic locks (synchronized), explicit locks (ReentrantLock), read/write locks (ReentrantReadWriteLock), and advanced constructs like StampedLock, LockSupport, and various atomic classes (AtomicInteger, AtomicReference, etc.) with code examples.

The article examines coordination utilities such as CountDownLatch, CyclicBarrier, Semaphore, Exchanger, and ThreadLocalRandom, illustrating their usage through practical examples.

Executor frameworks are covered, describing ThreadPoolExecutor, ScheduledThreadPoolExecutor, ForkJoinPool, and CompletableFuture, highlighting task submission methods, scheduling, and asynchronous programming patterns.

Finally, it reviews Java's blocking queue implementations (ArrayBlockingQueue, LinkedBlockingQueue, PriorityBlockingQueue, DelayQueue, SynchronousQueue, LinkedTransferQueue, LinkedBlockingDeque) and their core operations, providing insight into internal mechanisms and performance considerations.

public class Example {
    public static void main(String[] args) throws Exception {
        ExecutorService executor = Executors.newFixedThreadPool(2);
        Future
f = executor.submit(() -> "Hello, Concurrency!");
        System.out.println(f.get());
        executor.shutdown();
    }
}