int count=0;  

  Scanner sum=new Scanner(System.in);

  System.out.println("请输入一个整数");

  int sum1=sum.nextInt();

  if(sum1>=0){

while(sum1!=0){

count++;

sum1/=sum1;

}

System.out.println("是个"+count+"位的数");

  }else{

  System.out.println("输入有误");

  }