CountDownLatch 闭锁演示
import java.util.concurrent.CountDownLatch;/** * CountDownLatch 闭锁演示 * 闭锁的作用相当于一扇门：在闭锁到达结束状态（getCount()=0）前，这扇门一直是关闭的，并且没有任何线程能通过。 * 当到达结束状态时，这扇门会打开并允许所有的线程通过（可以继续执行await()之后的代码）。 * 当闭锁到达结束状态后，将不会再改变状态，因此这扇门将永远保持打开状态。 * **/public class TestHarness {public long timeTasks(int nThreads, final Runnable task) throws InterruptedException{final CountDownLatch startGate = new CountDownLatch(1); final CountDownLatch endGate = new CountDownLatch(nThreads); for(int i = 0; i < nThreads; i++){Thread thread = new Thread(){public void run(){try {System.out.println("Before:S="+startGate.getCount()+"E="+endGate.getCount());startGate.await();//使当前线程在锁存器倒计数至零之前一直等待，除非线程被中断。System.out.println("After：S="+startGate.getCount()+"E="+endGate.getCount());try {System.out.println("task run!");task.run();} finally{System.out.println("End Gate countDown()");endGate.countDown();}} catch (InterruptedException e) {}}};thread.start();}long start = System.nanoTime();//返回最准确的可用系统计时器的当前值，以毫微秒为单位。System.out.println("开启启动门!");startGate.countDown();//递减锁存器的计数，如果计数到达零，则释放所有等待的线程。endGate.await();//使当前线程在锁存器倒计数至零之前一直等待，除非线程被中断。System.out.println("End Gate await()");long end = System.nanoTime();return end-start;} public static void main(String[] args) {MyThread thread=new MyThread("线程A");TestHarness testHarness = new TestHarness();try {long time = testHarness.timeTasks(10, thread);System.out.println("It's cost time:"+time);} catch (Exception e) {System.out.println("Exception Accured!");}}}
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