对main线程使用join方法，为什么main线程处于一直阻塞状态？

Question

public class JoinTest {public static void main(String[] args) throws InterruptedException {    MyThread3 thread=new MyThread3();    thread.start();    //thread.join(1);//将主线程加入到子线程后面，不过如果子线程在1毫秒时间内没执行完，则主线程便不再等待它执行完，进入就绪状态，等待cpu调度    System.out.println(Thread.currentThread());    Thread.currentThread().join();    for(int i=0;i<30;i++){        System.out.println(Thread.currentThread().getName() + "线程第" + i + "次执行！");    }}}class MyThread3 extends Thread {@Overridepublic void run() {        for (int i = 0; i < 1000; i++) {        try {            System.out.println(this.getName() + "线程第" + i + "次执行！");            Thread.sleep(1);        } catch (InterruptedException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }}}

Answer 1

那你得先知道join函数是干嘛用的啊！我们先来看看文档：

/**

 * Waits for this thread to die.

 *

 * <p> An invocation of this method behaves in exactly the same

 * way as the invocation

 *

 * <blockquote>

 * {@linkplain #join(long) join}{@code (0)}

 * </blockquote>

 *

 * @throws  InterruptedException

 *          if any thread has interrupted the current thread. The

 *          <i>interrupted status</i> of the current thread is

 *          cleared when this exception is thrown.

 */

第一句话就说了Waits for this thread to die，你在主线程上执行"我要等到主线程结束，当前线程才能结束"，这不成死循环了么。