定义

等待该线程终止，比如A线程调用了B线程的join，那么A线程要等到B线程执行完后，才可以继续执行。

示例

public class JoinDemo {    static class JoinThread1 implements Runnable {        Thread thread;        public JoinThread1(Thread thread) {            this.thread = thread;        }        @Override        public void run() {            System.out.println("thread1 start");            try {                thread.join();                System.out.println("thread1 end");            } catch (InterruptedException e) {                e.printStackTrace();            }        }    }    static class JoinThread2 implements Runnable {        @Override        public void run() {            System.out.println("thread2 start");            try {                Thread.sleep(10000);                System.out.println("thread2 end");            } catch (InterruptedException e) {                e.printStackTrace();            }        }    }    public static void main(String[] args) {        JoinThread2 joinThread2 = new JoinThread2();        Thread thread2 = new Thread(joinThread2);        JoinThread1 joinThread1 = new JoinThread1(thread2);        Thread thread1 = new Thread(joinThread1);        thread1.start();        thread2.start();    }}

运行结果如下：

线程1执行的时候，调用线程2的join，线程1不休眠，线程2休眠了10秒，从结果看出来，线程2执行完后，线程1才执行完。