join(), 当前线程暂停, 等待指定的线程执行结束后, 当前线程再继续* join(int), 可以等待指定的毫秒之后继续    *             final Thread t1 = new Thread() {                public void run() {                    for(int i = 0; i < 50; i++) {                        System.out.println(getName() + "...aaaaaaaaaaaaaaaaaaaaaa");                        try {                            Thread.sleep(10);                        } catch (InterruptedException e) {                            e.printStackTrace();                        }                    }                }            };            Thread t2 = new Thread() {                public void run() {                    for(int i = 0; i < 50; i++) {                        if(i == 2) {                            try {                                //t1.join();                        //插队,加入                                t1.join(30);                        //加入,有固定的时间,过了固定时间,继续交替执行                                Thread.sleep(10);                            } catch (InterruptedException e) {                                e.printStackTrace();                            }                        }                        System.out.println(getName() + "...bb");                    }                }            };            t1.start();            t2.start();