java 多线程 主线程等待子线程结束

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;


public class ExcetuorDemo2 {


public static void main(String[] args) {
ExecutorService service = Executors.newFixedThreadPool(5);

CountDownLatch cdl = new CountDownLatch(5);

Handler t1 = new Handler(cdl);
Handler t2 = new Handler(cdl);
Handler t3 = new Handler(cdl);
Handler t4 = new Handler(cdl);
Handler t5 = new Handler(cdl);

service.execute(t1);
service.execute(t2);
service.execute(t3);
service.execute(t4);
service.execute(t5);

service.shutdown();
try {
cdl.await();
} catch (InterruptedException e) {
e.printStackTrace();
}

System.out.println("over");
}
}


class Handler implements Runnable {
CountDownLatch cdl;

public Handler(CountDownLatch cdl){
this.cdl = cdl;
}

@Override
public void run() {
for(int i=0;i<1;i++){
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName() + "   " + i);
}
cdl.countDown();
}

}