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