java 線程join()方法學習筆記

一個線程可以在其它線程之上調用join()方法，其效果是等待一段時間直到第二個線程結束才繼續執行。如果某個線程在另一個線程t上調用t.join()，此線程將被掛起，直到目標線程t結束才恢復(即t.isAlive()返回假)。

也可以在調用join()方法時帶上一個超時參數（單位可以試毫秒，或者毫秒和納秒），這樣如果目標線程在這段時間到期時還沒有結束的話，join()方法總能返回。

對join()方法的調用可以被中斷，做法是在調用線程上調用interrupted()方法，這時需要用到try-catch子句。

class Sleeper extends Thread{
	private int duration;
	public Sleeper(String name,int sleepTime) {
		super(name);
		duration=sleepTime;
		start();
	}
	public void run() {
		try {
			sleep(duration);
		}catch(InterruptedException e) {
			System.out.println(getName()+" was interrupted. "+" is interrupted: "+isInterrupted());
			return;
		}
		System.out.println(getName()+" has awakened");
	}
}
class Joiner extends Thread{
	private Sleeper sleeper;
	public Joiner(String name,Sleeper sleeper) {
		super(name);
		this.sleeper=sleeper;
		start();
	}
	public void run() {
		try {
			sleeper.join();
		}catch(InterruptedException e) {
			System.out.println("Interrupted");
		}
		System.out.println(getName()+" join completed");
	}
}
public class Joining {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
        Sleeper sleepy=new Sleeper("Sleepy",1500),
        		grumpy=new Sleeper("grumpy",1500);
        Joiner dopey=new Joiner("Dopey",sleepy),
        		doc=new Joiner("Doc",grumpy);
        grumpy.interrupt();
	}

}
/*
grumpy was interrupted.  is interrupted: false
Doc join completed
Sleepy has awakened
Dopey join completed
*/