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("它是一个"+count+"位的数！");

}

else

{

    System.out.println("输出有误！");

}

}

}

}