哪里错了??求指教
public class HelloWorld{
public static void main(String[] args){
int num = 9999;
int count = 0;
if(num>0 && num<=999999999) {
do{
num/=10;
count++;
}
while(num!=0);
System.out.println("它是个"+count+"位的数!");
}
else{
System.out.println("输入有误!");
}
}
}