指定线程执行的顺序---join()

线程T1，T2，T3分别启动，如何让其执行顺序变为T3>T2>T1：

线程1：

package test6;

public class Thread1 extends Thread{

    private Thread thread2;
    public Thread1(Thread thread2){
        this.thread2=thread2;
    }
    @Override
    public void run(){
        try {
            thread2.join();
            System.out.println("线程1在执行");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

线程2：

package test6;

public class Thread2 extends Thread{

    private Thread thread3;
    public Thread2(Thread thread3){
        this.thread3=thread3;
    }
    @Override
    public void run(){
        try {
            thread3.join();
            System.out.println("线程2在执行");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

线程3：

package test6;

public class Thread3 extends Thread{

    @Override
    public void run(){
        try {
            System.out.println("线程3在执行。。。");
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

执行：

package test6;

public class Run {

    public static void main(String[] args) {
        Thread3 t3=new Thread3();
        Thread2 t2=new Thread2(t3);
        Thread1 t1=new Thread1(t2);
        t1.start();
        t2.start();
        t3.start();
    }
}

如图：启动顺序为t1,t2,t3.但是使用join后，执行顺序为t3,t2,t1

join的作用：使当前线程等正在执行的线程执行完。join内部调用的是wait方法没，所以释放锁。sleep不释放锁。