Thread类join()方法重载了3次.分别是
join()throws InterruptedException; //无参数的join()等价于join(0),作用是一直等待该线程死亡 join(long millis, int nanos) throws InterruptedException; //最多等待该线程死亡millis毫秒 join(long millis, int nanos) throws InterruptedException ; //最多等待该线程死亡millis毫秒加nanos纳秒
join()的作用其实java doc 说的很清楚了:Waits for this thread to die.翻译过来就是等待这个线程死亡,如果join的线程不死亡,程序就会阻塞在那里.
实例:现在有T1、T2、T3三个线程，你怎样保证T2在T1执行完后执行，T3在T2执行完后执行？
import java.util.Date;
class RunnableJob implements Runnable {
@Override
public void run() {
Thread thread = Thread.currentThread();
System.out.println(thread.getName() + " start" + " at "
+ new Date());
try {
Thread.sleep(1000);
System.out.println(thread.getName() + " end" + " at "
+ new Date());
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
public class BasicTest {
public static void main(String[] args) throws InterruptedException {
//初始化
RunnableJob runnableJob = new RunnableJob();
Thread T1 = new Thread(runnableJob, "T1");
Thread T2 = new Thread(runnableJob, "T2");
Thread T3 = new Thread(runnableJob, "T3");
//T2在T1执行完后执行，T3在T2执行完后执行
T1.start();
T1.join();
T2.start();
T2.join();
T3.start();
}
}
终端输出
T1 start at Fri Sep 05 16:24:12 CST 2014 T1 end at Fri Sep 05 16:24:13 CST 2014 T2 start at Fri Sep 05 16:24:13 CST 2014 T2 end at Fri Sep 05 16:24:14 CST 2014 T3 start at Fri Sep 05 16:24:14 CST 2014 T3 end at Fri Sep 05 16:24:15 CST 2014
时间： 2024-11-04 09:10:42