# [题目描述](https://leetcode-cn.com/problems/contains-duplicate-iii/)  话不多说 直接上代码，复习一下Lock、synchronized、还有CountDownLatch、Semaphore、CyclicBarrier等工具类 ## ReentrantLock + Condition ```java class Foo { ReentrantLock lock = new ReentrantLock(); Condition a = lock.newCondition(); Condition b = lock.newCondition(); Condition c = lock.newCondition(); private volatile int status = 1; public Foo() { } public void first(Runnable printFirst) throws InterruptedException { try{ lock.lock(); while(status!=1){ a.await(); } status = 2; printFirst.run(); b.signal(); }finally{ lock.unlock(); } // printFirst.run() outputs "first". Do not change or remove this line. } public void second(Runnable printSecond) throws InterruptedException { try{ lock.lock(); while(status!=2){ b.await(); } status = 3; printSecond.run(); c.signal(); }finally{ lock.unlock(); } // printSecond.run() outputs "second". Do not change or remove this line. } public void third(Runnable printThird) throws InterruptedException { try{ lock.lock(); while(status!=3){ c.await(); } status = 1; printThird.run(); a.signal(); }finally{ lock.unlock(); } // printThird.run() outputs "third". Do not change or remove this line. } } ``` ## LockSupport ```java class Foo { static Thread aThread = null,bThread = null,cThread = null; private volatile int status = 1; public Foo() { } public void first(Runnable printFirst) throws InterruptedException { aThread = Thread.currentThread(); printFirst.run(); status = 2; LockSupport.unpark(bThread); // printFirst.run() outputs "first". Do not change or remove this line. // printFirst.run(); } public void second(Runnable printSecond) throws InterruptedException { bThread = Thread.currentThread(); while(status!=2) LockSupport.park(); printSecond.run(); status = 3; LockSupport.unpark(cThread); // printSecond.run() outputs "second". Do not change or remove this line. // printSecond.run(); } public void third(Runnable printThird) throws InterruptedException { cThread = Thread.currentThread(); while(status!=3) LockSupport.park(); printThird.run(); status = 1; LockSupport.unpark(aThread); // printThird.run() outputs "third". Do not change or remove this line. // printThird.run(); } } ``` ## synchronized + wait/notify ```java class Foo { Object lock = new Object(); private volatile int status = 1; public Foo() { } public void first(Runnable printFirst) throws InterruptedException { synchronized(lock){ while(status!=1){ lock.wait(); } printFirst.run(); status = 2; lock.notifyAll(); } // printFirst.run() outputs "first". Do not change or remove this line. } public void second(Runnable printSecond) throws InterruptedException { synchronized(lock){ while(status!=2){ lock.wait(); } printSecond.run(); status = 3; lock.notifyAll(); } // printSecond.run() outputs "second". Do not change or remove this line. } public void third(Runnable printThird) throws InterruptedException { synchronized(lock){ while(status!=3){ lock.wait(); } printThird.run(); status = 1; lock.notifyAll(); } // printThird.run() outputs "third". Do not change or remove this line. } } ``` ## Semaphore ```java class Foo { Semaphore s = new Semaphore(1); private volatile int status = 1; public Foo() { } public void first(Runnable printFirst) throws InterruptedException { while(status!=1){ } s.acquire(); // printFirst.run() outputs "first". Do not change or remove this line. printFirst.run(); status = 2; s.release(); } public void second(Runnable printSecond) throws InterruptedException { while(status!=2){ } s.acquire(); // printFirst.run() outputs "first". Do not change or remove this line. printSecond.run(); status = 3; s.release(); // printSecond.run() outputs "second". Do not change or remove this line. } public void third(Runnable printThird) throws InterruptedException { while(status!=3){ } s.acquire(); // printFirst.run() outputs "first". Do not change or remove this line. printThird.run(); status = 1; s.release(); // printThird.run() outputs "third". Do not change or remove this line. } } ``` ## CountDownLatch ```java class Foo { CountDownLatch aLatch = new CountDownLatch(1); CountDownLatch bLatch = new CountDownLatch(1); public Foo() { } public void first(Runnable printFirst) throws InterruptedException { // printFirst.run() outputs "first". Do not change or remove this line. printFirst.run(); aLatch.countDown(); } public void second(Runnable printSecond) throws InterruptedException { aLatch.await();//aLatch计数器为1，当线程1打印完毕后--为0，这里不再被阻塞 线程2开始打印 // printSecond.run() outputs "second". Do not change or remove this line. printSecond.run(); bLatch.countDown(); } public void third(Runnable printThird) throws InterruptedException { bLatch.await();//bLatch计数器为1，当线程1打印完毕后--为0，这里不再被阻塞 线程2开始打印 // printThird.run() outputs "third". Do not change or remove this line. printThird.run(); } } ``` ## CyclicBarrier ```java class Foo { CyclicBarrier cy1 = new CyclicBarrier(2); CyclicBarrier cy2 = new CyclicBarrier(2); public Foo() { } public void first(Runnable printFirst) throws InterruptedException { // printFirst.run() outputs "first". Do not change or remove this line. printFirst.run(); try{ cy1.await(); }catch(BrokenBarrierException e){ e.printStackTrace(); } } public void second(Runnable printSecond) throws InterruptedException { try{ cy1.await(); //线程1已经通过了cy1表示线程1已经打印完毕 //当线程1 和2都到达此处后 线程2才开始打印 printSecond.run(); cy2.await();//线程2到达屏障2 }catch(BrokenBarrierException e){ e.printStackTrace(); } // printSecond.run() outputs "second". Do not change or remove this line. } public void third(Runnable printThird) throws InterruptedException { try{ cy2.await();//线程2打印完毕后线程3才开始打印 printThird.run(); }catch(BrokenBarrierException e){ e.printStackTrace(); } // printThird.run() outputs "third". Do not change or remove this line. } } ```