请大神们回答，为什么一直提示我输出错误
public class HelloWorld{
public static void main(String[] args){
int num = 999;
int count = 0;
if(num>=0&&num<=999999999)
{
while(num!=0)
{
count++;
num=num/10;
}
System.out.println("它是个"+ count +"位的数!");
}
else
{
System.out.println("输入错误");
}
}
}
