public class HelloWorld{

public static void main(String[] args){

int num = 9999;

int count = 0;

  if(num>0 && num<=999999999) {

  do{

       num/=10;

       count++;

   }

while(num！=0);

System.out.println("它是个"+count+"位的数！");

}

else{

    System.out.println("输入有误！")；

}

}

}