public static void main(String[] args){
		int len=20;
		Thread[] arr=new Thread[len];
		arr[0]=new Thread(new JoinDemo(),"0");
		for(int i=1;i<len;i++){
			arr[i]=new Thread(new JoinDemo(arr[i-1]),String.valueOf(i));
		}
		Thread free=new Thread(new JoinDemo(),"I'm free");
		for(int j=0;j<arr.length;j++){
			arr[j].start();
		}
		free.start();
	}