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(); } } }
