Java 队列

public class ExecutorTest {
    private static ExecutorService es = new ThreadPoolExecutor(2,
            100, 1000, TimeUnit.MILLISECONDS
            , new ArrayBlockingQueue<>(10));
    public static void main(String[] args) {
        for (int i = 0; i < 10; i++) {
            es.submit(new MyThread());
        }
    }
    static class MyThread implements Runnable {
        @Override
        public void run() {
            for (; ; ) {
                System.out.println("Thread name=" + Thread.currentThread().getName());
                try {
                    TimeUnit.SECONDS.sleep(2);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

private static ExecutorService es = Executors.newCachedThreadPool();

/**
 * Creates a thread pool that creates new threads as needed, but
 * will reuse previously constructed threads when they are
 * available.  These pools will typically improve the performance
 * of programs that execute many short-lived asynchronous tasks.
 * Calls to {@code execute} will reuse previously constructed
 * threads if available. If no existing thread is available, a new
 * thread will be created and added to the pool. Threads that have
 * not been used for sixty seconds are terminated and removed from
 * the cache. Thus, a pool that remains idle for long enough will
 * not consume any resources. Note that pools with similar
 * properties but different details (for example, timeout parameters)
 * may be created using {@link ThreadPoolExecutor} constructors.
 *
 * @return the newly created thread pool
 */
public static ExecutorService newCachedThreadPool() {
    return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
                                  60L, TimeUnit.SECONDS,
                                  new SynchronousQueue<Runnable>());
}

public class ExecutorTest {
    private static ExecutorService es = new ThreadPoolExecutor(2,
            100, 1000, TimeUnit.MILLISECONDS
            , new SynchronousQueue<>());
    private static ExecutorService es2 = Executors.newCachedThreadPool();
    public static void main(String[] args) {
        for (int i = 0; i < 10; i++) {
            es.submit(new MyThread());
        }
    }
    static class MyThread implements Runnable {
        @Override
        public void run() {
            for (; ; ) {
                System.out.println("Thread name=" + Thread.currentThread().getName());
                try {
                    TimeUnit.SECONDS.sleep(2);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

* <p>Synchronous queues are similar to rendezvous channels used in
* CSP and Ada. They are well suited for handoff designs, in which an
* object running in one thread must sync up with an object running
* in another thread in order to hand it some information, event, or
* task.

* A bounded {@linkplain BlockingQueue blocking queue} backed by an
* array.  This queue orders elements FIFO (first-in-first-out).  The
* <em>head</em> of the queue is that element that has been on the
* queue the longest time.  The <em>tail</em> of the queue is that
* element that has been on the queue the shortest time. New elements
* are inserted at the tail of the queue, and the queue retrieval
* operations obtain elements at the head of the queue.

* <dt>Queuing</dt>
*
* <dd>Any {@link BlockingQueue} may be used to transfer and hold
* submitted tasks.  The use of this queue interacts with pool sizing:
*
* <ul>
*
* <li> If fewer than corePoolSize threads are running, the Executor
* always prefers adding a new thread
* rather than queuing.</li>
*
* <li> If corePoolSize or more threads are running, the Executor
* always prefers queuing a request rather than adding a new
* thread.</li>
*
* <li> If a request cannot be queued, a new thread is created unless
* this would exceed maximumPoolSize, in which case, the task will be
* rejected.</li>

public Future<?> submit(Runnable task) {
    if (task == null) throw new NullPointerException();
    RunnableFuture<Void> ftask = newTaskFor(task, null);
    execute(ftask);
    return ftask;
}

public void execute(Runnable command) {
    if (command == null)
        throw new NullPointerException();
    /*
     * Proceed in 3 steps:
     *
     * 1. If fewer than corePoolSize threads are running, try to
     * start a new thread with the given command as its first
     * task.  The call to addWorker atomically checks runState and
     * workerCount, and so prevents false alarms that would add
     * threads when it shouldn't, by returning false.
     *
     * 2. If a task can be successfully queued, then we still need
     * to double-check whether we should have added a thread
     * (because existing ones died since last checking) or that
     * the pool shut down since entry into this method. So we
     * recheck state and if necessary roll back the enqueuing if
     * stopped, or start a new thread if there are none.
     *
     * 3. If we cannot queue task, then we try to add a new
     * thread.  If it fails, we know we are shut down or saturated
     * and so reject the task.
     */
    int c = ctl.get();
    if (workerCountOf(c) < corePoolSize) {
        if (addWorker(command, true))
            return;
        c = ctl.get();
    }
    if (isRunning(c) && workQueue.offer(command)) {
        int recheck = ctl.get();
        if (! isRunning(recheck) && remove(command))
            reject(command);
        else if (workerCountOf(recheck) == 0)
            addWorker(null, false);
    }
    else if (!addWorker(command, false))
        reject(command);
}