java--java.lang.Thread.join() 方法

Thread類join()方法重載了3次.分別是

join()throws InterruptedException;  //無參數的join()等價於join(0),做用是一直等待該線程死亡

join(long millis, int nanos) throws InterruptedException;  //最多等待該線程死亡millis毫秒

join(long millis, int nanos) throws InterruptedException ; //最多等待該線程死亡millis毫秒加nanos納秒

 

 

join()的做用其實java doc 說的很清楚了:Waits for this thread to die.翻譯過來就是等待這個線程死亡,若是join的線程不死亡,程序就會阻塞在那裏.

實例:如今有T一、T二、T3三個線程，你怎樣保證T2在T1執行完後執行，T3在T2執行完後執行？

　　　　　　

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執行完後執行，T3在T2執行完後執行
        T1.start();
        T1.join();
        T2.start();
        T2.join();
        T3.start();
    }

}

 

終端輸出

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