countDownLatch 线程辅助类，是一个线程计数类，用来线程同步，每当一个线程执行完成后，就是加1，当达到计数，就算执行完成。初始值必须小于等于要执行的线程数，为0 是，不其作用，大于0，小于等于线程数时，为同步线程数，当大于线程数时，为死循环（可能不对）反正就是一直等待。- import java.text.SimpleDateFormat;
- import java.util.Date;
- import java.util.concurrent.CountDownLatch;
-
- public class T1 {
- final static SimpleDateFormat sdf = new SimpleDateFormat(
- "yyyy-MM-dd HH:mm:ss");
-
- public static void main(String[] args) throws Exception {
- CountDownLatch countDownLatch = new CountDownLatch(3);
- Worker w1 = new Worker("w1", 2000, countDownLatch);
- Worker w2 = new Worker("w2", 5000, countDownLatch);
- w1.start();//
- w2.start();//
- countDownLatch.await();// 等待所有工人完成工作
- System.out.println("all work done at " + sdf.format(new Date()));
- }
-
- static class Worker extends Thread {
- String workerName;
- int workTime;
- CountDownLatch latch;
-
- public Worker(String workerName, int workTime, CountDownLatch latch) {
- this.workerName = workerName;
- this.workTime = workTime;
- this.latch = latch;
- }
-
- @Override
- public void run() {
- System.out.println("Worker " + workerName + " do work begin at "
- + sdf.format(new Date()));
- try {
- Thread.sleep(workTime);
- } catch (InterruptedException e) {
- e.printStackTrace();
- }
- System.out.println("Worker " + workerName + " do work complete at "
- + sdf.format(new Date()));
- latch.countDown();// 工人完成工作，计数器减一
- }
- }
- }
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