CountDownLatch
這個類內部有計數器，當計數器爲0時纔會執行下一步操作。這個計數值就是你需要同步的步驟數，通過構造方法傳入。
案例：
public class CountDownLatchDemo {
final static SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
public static void main(String[] args) throws InterruptedException {
//實現兩個工人工作，必須兩個工作任務同時完成才能進行下一步。
//採用CountDownLatch類來實現
CountDownLatch latch = new CountDownLatch(2);// 計數器賦值爲2
Worker worker1 = new Worker("楊楊", 5000, latch);
Worker worker2 = new Worker("黃黃", 8000, latch);
worker1.start();//開始工作
worker2.start();//開始工作
latch.await();//等待所有人完成工程
System.out.println("所有人工作已經完成");
}
static class Worker extends Thread{
private String workername;
private int worktime;
private CountDownLatch latch;
public void run(){
System.out.println("Worker:"+workername+" do work begin at "+sdf.format(new Date()));
doWork();
System.out.println("Worker:"+workername+" do work end at "+sdf.format(new Date()));
latch.countDown();//計數器減一
}
public Worker(String workername,int worktime,CountDownLatch latch){
this.workername = workername;
this.worktime = worktime;
this.latch = latch;
}
private void doWork(){
try{
Thread.sleep(worktime);
}catch(InterruptedException e){
e.printStackTrace();
}
}
}
}