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("它是个"+ count+"位的数!");
} else{
System.out.println("输入有误!");
}
99/10=9, OK?
0.999其是0