Java中的join

You have thread T1, T2 and T3, how will you ensure that thread T2 run after T1 and thread T3 run after T2?

你有三个线程T1，T2，T3，如何使得T1执行完后再执行T2，T2执行完后再执行T3？

以下是一个可能的实现方法：

public class ThreadJoin implements Runnable {
	
	private final Thread joinTarget;
	public ThreadJoin(Thread joinTarget) {
		this.joinTarget = joinTarget;
	}
	
	@Override
	public void run() {
		if(joinTarget != null) {
			try {
				joinTarget.join();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			
			System.out.println("Join complete " + Thread.currentThread().getName());
		}
	}
	
	private static class MyThread implements Runnable {
		@Override
		public void run() {
			System.out.println("MyThread");
		}
	}	
	
	public static void main(String[] args) {
		Thread t1 = new Thread(new MyThread(), "Thread1");
		Thread t2 = new Thread(new ThreadJoin(t1), "Thread2");
		Thread t3 = new Thread(new ThreadJoin(t2), "Thread3");
		t1.start();
		t2.start();
		t3.start();
	}
}