单层while循环搞定的,为啥说运行成功,输出错误???

单层while循环搞定的,为啥说运行成功,输出错误 public class HelloWorld{ public static void main(String[] args){ int num = 999; int count = 0; while(num > 0){    num /= 10;    count++; } System.out.println("它是个" + count + "位的数! "); } }