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!");

}

}

}