LeetCode（多线程）- 1117. H2O 生成

题目链接：​​点击打开链接​​

题目大意：注意每一题的外部调用多线程，如果没特殊说明，想成每一个字符都是一个线程，只是装配的类是同一个，所以我们写的属性是能被共享有效的。

解题思路：略。

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AC 代码

// 方法1:Semaphore
class H2O {

    private Semaphore hSema = new Semaphore(2);

    private Semaphore oSema = new Semaphore(0);

    public H2O() {

    }

    public void hydrogen(Runnable releaseHydrogen) throws InterruptedException {
        hSema.acquire();
        releaseHydrogen.run();
        oSema.release();
    }

    public void oxygen(Runnable releaseOxygen) throws InterruptedException {
        oSema.acquire(2);
        releaseOxygen.run();
        hSema.release(2);
    }
}

// 方法2:Semaphore+CyclicBarrier
class H2O {

    private Semaphore hSema = new Semaphore(2);

    private Semaphore oSema = new Semaphore(1);

    private CyclicBarrier cb = new CyclicBarrier(3);

    public H2O() {

    }

    public void hydrogen(Runnable releaseHydrogen) throws InterruptedException {
        hSema.acquire();
        try {
            cb.await();
        } catch (BrokenBarrierException e) {
            e.printStackTrace();
        }
        releaseHydrogen.run();
        hSema.release();
    }

    public void oxygen(Runnable releaseOxygen) throws InterruptedException {
        oSema.acquire();
        try {
            cb.await();
        } catch (BrokenBarrierException e) {
            e.printStackTrace();
        }
        releaseOxygen.run();
        oSema.release();
    }
}

// 方法3:ReentrantLock+Condition
class H2O {

    private int oCnt = 0;

    private int hCnt = 0;

    private ReentrantLock lock = new ReentrantLock();

    private Condition con = lock.newCondition();

    public H2O() {

    }

    public void hydrogen(Runnable releaseHydrogen) throws InterruptedException {
        lock.lock();
        try {
            while (hCnt == 2) {
                con.await();
            }
            hCnt++;
            if (hCnt == 2 && oCnt == 1) {
                hCnt = 0;
                oCnt = 0;
            }
            releaseHydrogen.run();
            con.signalAll();
        } finally {
            lock.unlock();
        }

    }

    public void oxygen(Runnable releaseOxygen) throws InterruptedException {
        lock.lock();
        try {
            while (oCnt == 1) {
                con.await();
            }
            oCnt++;
            if (hCnt == 2 && oCnt == 1) {
                hCnt = 0;
                oCnt = 0;
            }
            releaseOxygen.run();
            con.signalAll();
        } finally {
            lock.unlock();
        }

    }
}

// 方法4:synchronized
class H2O {

    private int state = 0;

    private Object obj = new Object();

    public H2O() {

    }

    public void hydrogen(Runnable releaseHydrogen) throws InterruptedException {
        synchronized (obj) {
            while (state == 2) {
                obj.wait();
            }
            state++;
            releaseHydrogen.run();
            obj.notifyAll();
        }

    }

    public void oxygen(Runnable releaseOxygen) throws InterruptedException {
        synchronized (obj) {
            while (state != 2) {
                obj.wait();
            }
            state = 0;
            releaseOxygen.run();
            obj.notifyAll();
        }

    }
}

// 方法5:BlockingQueue
class H2O {

    private AtomicInteger cnt = new AtomicInteger();

    private BlockingQueue<Integer> hQ = new LinkedBlockingDeque<>(2);

    private BlockingQueue<Integer> oQ = new LinkedBlockingDeque<>(1);

    public H2O() {

    }

    public void hydrogen(Runnable releaseHydrogen) throws InterruptedException {
        hQ.put(1);
        releaseHydrogen.run();
        common();
    }

    public void oxygen(Runnable releaseOxygen) throws InterruptedException {
        oQ.put(1);
        releaseOxygen.run();
        common();
    }

    private void common() {
        cnt.incrementAndGet();
        if (cnt.intValue() == 3) {
            cnt.set(0);
            hQ.clear();
            oQ.clear();
        }
    }
}