多線程---模擬接力賽跑

//接力賽跑的線程，實現Runnable
public class MyRunnable implements Runnable{
    static int num = 10;
    private String thread;
    Object lock = new Object();
    public void run() {
        while(true) {
            synchronized (lock) {
                if(num == 0) {
                    System.out.println("比賽結束！");
                    break;
                }
                thread = Thread.currentThread().getName();
                System.out.println(thread+"拿到了接力棒！");
                num--;            
                for(int i =1;i<=10;i++) {
                    try {
                        Thread.sleep(10);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    System.out.println(thread+"跑了"+(i*10));
                }
                return;
            }
        }
    }
}

//測試類
public class Test {
    public static void main(String[] args) throws InterruptedException {
        MyRunnable m = new MyRunnable();
        Thread thread1 = new Thread(m,"1號選手");
        Thread thread2 = new Thread(m,"2號選手");
        Thread thread3 = new Thread(m,"3號選手");
        Thread thread4 = new Thread(m,"4號選手");
        Thread thread5 = new Thread(m,"5號選手");
        Thread thread6 = new Thread(m,"6號選手");
        Thread thread7 = new Thread(m,"7號選手");
        Thread thread8 = new Thread(m,"8號選手");
        Thread thread9 = new Thread(m,"9號選手");
        Thread thread10 = new Thread(m,"10號選手");
        thread1.start();
        thread2.start();
        thread3.start();
        thread4.start();
        thread5.start();
        thread6.start();
        thread7.start();
        thread8.start();
        thread9.start();
        thread10.start();
        
    }
}

運行結果：

 

 

 

 

問題：無法實現少於十人的接力賽跑，實現不連續出現的情況！