请问哪儿错了？
public class HelloWorld{
public static void main(String[] args){
int num = 999;
int count = 0;
if(num>0 && num<=999999999)
{
while(num !=0)
{
num/=10;
count++;
}
System.out.println("它是个"+count+"位的数");
}
else
{
System.out.println("输入错误");
}
}
}
