Java线程池由浅入深掌握到精通

//演示关闭线程池
public class ShutDown {
    public static void main(String[] args) throws InterruptedException {
        ExecutorService executorService = Executors.newFixedThreadPool(10);
        for (int i = 0; i < 500; i++) {
            executorService.execute(new ShutDownTask());
        }
        Thread.sleep(1500);
//        executorService.shutdown();
//        System.out.println(executorService.isShutdown());
        executorService.awaitTermination(3L, TimeUnit.SECONDS);
    }
}
class ShutDownTask implements Runnable{

    @Override
    public void run() {
        try {
            Thread.sleep(500);
            System.out.println(Thread.currentThread().getName());
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

//暂停线程池
 pauseAbleThreadPool.pause();
 //恢复线程池
 pauseAbleThreadPool.resume();

//演示每个任务执行前后放钩子函数
public class PauseAbleThreadPool extends ThreadPoolExecutor {
    private final ReentrantLock lock = new ReentrantLock();
    private Condition unpaused = lock.newCondition();
    private boolean isPaused;

    public PauseAbleThreadPool(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
    }

    public PauseAbleThreadPool(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory);
    }

    public PauseAbleThreadPool(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, RejectedExecutionHandler handler) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, handler);
    }

    public PauseAbleThreadPool(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory, RejectedExecutionHandler handler) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, handler);
    }

    @Override
    protected void beforeExecute(Thread t, Runnable r) {
        super.beforeExecute(t, r);
        lock.lock();
        try {
            while (isPaused) {
                unpaused.await();
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    private void pause() {
        lock.lock();
        try {
            isPaused = true;
        } finally {
            lock.unlock();
        }
    }

    public void resume() {
        lock.lock();
        try {
            isPaused = false;
            unpaused.signalAll();
        } finally {
            lock.unlock();
        }
    }

    public static void main(String[] args) throws InterruptedException {
        PauseAbleThreadPool pauseAbleThreadPool = new PauseAbleThreadPool(10, 20, 10l, TimeUnit.SECONDS, new LinkedBlockingQueue<>());
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                System.out.println("我被执行");
                try {
                    Thread.sleep(10);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        };
        for (int i = 0; i < 10000; i++) {
            pauseAbleThreadPool.execute(runnable);
        }
        Thread.sleep(1500);
        pauseAbleThreadPool.pause();
        System.out.println("线程池被暂停了");
        Thread.sleep(1500);
        pauseAbleThreadPool.resume();
        System.out.println("线程池被恢复了");

    }
}