多线程---模拟接力赛跑

//接力赛跑的线程，实现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("比赛结束！");
                    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;
            }
        }
    }
}

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

运行结果：

问题：无法实现少于十人的接力赛跑，实现不连续出现的情况！