现创建两个线程thread1和thread2，thread1运行时间短，thread2运行时间长，代码如下：
public static void main(String[] args) throws InterruptedException {Thread thread1 = new Thread(() -> {//运行时间短for (int i = 0; i < 3; i++) {System.out.println("Thread1");try {sleep(1000);} catch (InterruptedException e) {throw new RuntimeException(e);}}});Thread thread2 = new Thread(() -> {//运行时间长for (int i = 0; i < 3; i++) {System.out.println("Thread2");try {sleep(2000);} catch (InterruptedException e) {throw new RuntimeException(e);}}});thread1.start();thread2.start();for (int i = 0; i < 3; i++) {System.out.println("main");sleep(1000);}}现有如下join顺序：
1.
thread1.join();会使main线程阻塞，thread1与thread2同时运行，由于thread1运行时间短，则thread1会先结束，结束后thread2与main同时运行。
2.
thread2.join();会使mian线程阻塞，thread1与thread2同时运行，thread1结束后，thread2依然在运行，thread2结束后main才会运行。
3.
thread1.join();thread2.join();mian线程被阻塞，thread1与thread2先运行，thread1结束后thread2依然在运行，thread2结束后mian才运行。
4.
thread2.join();thread1.join();main线程被阻塞，thread1与thread2先运行，由于thread1先于thread2结束，则thread2结束后“thread1.join()”是无效语句，mian接着运行。
以上3，4的写法与2是等价的
