一个运行就会把CPU100的程序

package temple;
public class ThreadSafeTest implements Runnable {
    int num = 10; // 设置当前总票数
   
    public void run() {
        while (true) {
            if (num > 0) {
                try {
                    Thread.sleep(100);
                } catch (Exception e) {
                    e.printStackTrace();
                }
                System.out.println("tickets" + num--);
            }
        }
    }
   
    public static void main(String[] args) {
        ThreadSafeTest t = new ThreadSafeTest(); // 实例化类对象
        Thread tA = new Thread(t); // 以该类对象分别实例化4个线程
        Thread tB = new Thread(t);
        Thread tC = new Thread(t);
        Thread tD = new Thread(t);
        tA.start(); // 分别启动线程
        tB.start();
        tC.start();
        tD.start();
    }
}
这个代码，只要运行，CPU直接就100，什么毛病