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/=10;
?}
?System.out.println("它是個"+ count+"位的數(shù)！");
?} else{
?System.out.println("輸入有誤！");
?}