public class Pratice{
public static void main(String[] args){
int num = 999;
int count = 0;
if(num>=0&&num<=999999999){
?for(;num!=0;){
???? count++;
???? num=num/10;
?}
System.out.println("它是個(gè)" + count + "位的數(shù)！");
}
else {
??? System.out.println("number is invalid");
}
}
}

public class Practice{
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(gè)"+ count+"位的數(shù)！");
} else{
System.out.println("輸入有誤！");
}

}

}