Java concurrent包下线程池的三个特性【实例】

特性1：CountDownLatch

A synchronization aid that allows one or more threads to wait until a set of operations being performed in other threads completes.

private static void testCountDownLatch() throws InterruptedException {
    int count = 100;
    //等待主线程
    final CountDownLatch start = new CountDownLatch(1);
    final CountDownLatch end = new CountDownLatch(count);

    List<Thread> threads = new ArrayList<Thread>();
    for (int i = 1; i <= 100; i++)
    {
        threads.add(new Thread(new Runnable()
        {
            public void run()
            {
                try {
                    start.await();
                    System.out.println(Thread.currentThread().getName() + " do something done");
                } catch (InterruptedException e)
                {
                    e.printStackTrace();
                }
                finally
                {
                    end.countDown();
                }
            }
        }, "test-thread-" + i));
    }

    for (Thread th : threads) {
        th.start();
    }

    //开始所有线程
    start.countDown();
    //等待所有线程执行完毕
    end.await();

    System.out.println("main thread over!");
}

特性2：CyclicBarrier

线程栅栏 可重入

private static void testCy() {
    int count = 10;
    final CyclicBarrier cyclicBarrier = new CyclicBarrier(count, new Runnable()
    {
        public void run()
        {
            //每次所有线程到达栅栏后执行
            System.out.println(" last thread over!");
        }
    });

    List<Thread> threads = new ArrayList<Thread>();
    for (int i = 1; i <= count; i++)
    {
        threads.add(new Thread(new Runnable()
        {
            public void run()
            {
                try {
                    TimeUnit.SECONDS.sleep(1);
                    System.out.println(Thread.currentThread().getName() + " do something once!");
                    cyclicBarrier.await();
                    TimeUnit.SECONDS.sleep(1);
                    System.out.println(Thread.currentThread().getName() + " do something twice!");
                    cyclicBarrier.await();
                    TimeUnit.SECONDS.sleep(1);
                    System.out.println(Thread.currentThread().getName() + " do something third times!");
                    cyclicBarrier.await();
                } catch (InterruptedException e)
                {
                    e.printStackTrace();
                } catch (BrokenBarrierException e) {
                    e.printStackTrace();
                }
            }
        }, "test-thread-" + i));
    }

    for (Thread th : threads) {
        th.start();
    }
}

特性3：信号

private static void testSemaphore() {
    int count = 10;
    //同时允许连个线程执行
    final Semaphore semaphore = new Semaphore(2);

    List<Thread> threads = new ArrayList<Thread>();
    for (int i = 1; i <= count; i++)
    {
        threads.add(new Thread(new Runnable()
        {
            public void run()
            {
                try
                {
                    //获取信号
                    semaphore.acquire();
                    TimeUnit.SECONDS.sleep(1);
                    System.out.println(Thread.currentThread().getName() + " do something done!");
                } catch (InterruptedException e)
                {
                    e.printStackTrace();
                }
                finally
                {
                    semaphore.release();
                }
            }
        }, "test-thread-" + i));
    }

    for (Thread th : threads) {
        th.start();
    }
}

建议配合线程池使用。