java多线程里面的join()方法

//情况1 MainThread 在 NewThread.Join() 被调用后被阻塞，直到 NewThread 执行完毕才继续执行。
//情况2 如果join方法内有时间参数,经过试验可以得出，如果join（2000）方法里面加入了时间，比如2000，而对应的线程
//所要的时间是sleep(4000)4000毫秒，那么只是打断了2000毫秒后，join后面的代码会自动执行下去

public class ThreadJoinExample {
	public static void main(String[] args) {
		Thread t1 = new Thread(new MyRunnable(), "t1");
		Thread t2 = new Thread(new MyRunnable(), "t2");
		Thread t3 = new Thread(new MyRunnable(), "t3");
		t1.start();	
		try{
			System.out.println(Thread.currentThread().getName()+System.currentTimeMillis());
			t1.join(2000);
		}catch(InterruptedException e){
			e.printStackTrace();
		}
		System.out.println(Thread.currentThread().getName()+"t1是否在启动中" + t1.isAlive() +System.currentTimeMillis());
		System.out.println(Thread.currentThread().getName() +"t2是否在启动中" + t2.isAlive() +System.currentTimeMillis());
		t2.start();
		try{
			t2.join(2000);
			
		}catch(InterruptedException e){
			e.printStackTrace();
		}
		System.out.println(Thread.currentThread().getName() + "t2是否在启动中" + t2.isAlive() +System.currentTimeMillis());
		System.out.println("t1是否在启动中" + t1.isAlive());
		t3.start();
		try{
			System.out.println(Thread.currentThread().getName() + "t1是否在启动中" + t1.isAlive() +System.currentTimeMillis());
			System.out.println(Thread.currentThread().getName() + "t2是否在启动中" + t2.isAlive() +System.currentTimeMillis());
			t1.join();
			t2.join();
			t3.join();
		}catch (InterruptedException e){
			e.printStackTrace();
		}
		System.out.println("All threads are dead, exiting main thread");
	}

}
class MyRunnable implements Runnable{

	public void run() {
		System.out.println("thread start :::" + Thread.currentThread().getName());
		try{
			Thread.sleep(4000);
		} catch (InterruptedException e){
			e.printStackTrace();
		}
		System.out.println("Thread end :::" + Thread.currentThread().getName());
	}
	
}