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。