等待多线程完成的CountDownLatch

CountDownLatch允许一个或者多个线程等待其他线程完成操作。

• join方法实现，其原理在于不停检查join线程是否完成，如果存活就让当前线程等待，join线程中止后，this.notifyAll()方法调用
  /**

• 两个解析器，需要都解析完之后才能结束

• @author pengjunzhe
  */
  public class JoinCountDownLatchTest {
  public static void main(String[] args) throws InterruptedException {
  Thread parse1 = new Thread(new Runnable() {

       @Override
       public void run() {
           ;
       }
   });
   Thread parse2 = new Thread(new Runnable() {
  
       @Override
       public void run() {
           System.out.println("parser2 finish");
       }
   });
   parse1.start();
   parse2.start();
   parse1.join();
   parse2.join();
   System.out.println("all parse finished");
  

  }
  }

• CountDownLatch实现, countDown()方法计数器减一，await()方法阻塞当前线程，直到计数器变成零。

import java.util.concurrent.CountDownLatch;

/**
 * @author pengjunzhe
 */
public class CountDownLatchTest {
    static CountDownLatch countDownLatch = new CountDownLatch(2);

    public static void main(String[] args) throws InterruptedException {
        new Thread(new Runnable() {

            @Override
            public void run() {
                System.out.println(1);
                countDownLatch.countDown();
                System.out.println(2);
                countDownLatch.countDown();
            }
        }).start();
        countDownLatch.await();
        System.out.println(3);
    }
}