public static void main(String[] args) {
booleanNumber();

}
public static void booleanNumber(){
    Scanner sc  =   new Scanner(System.in);
    System.out.println("请输入数字:");
    int a   =   sc.nextInt();
    if(a<0||a>9999){
        System.out.println("输入错误！");
        return;
    }
    int count=0;
    while(a>0){
        a /=10;
        count++;
    }
    System.out.println("输入的是:"+count+"位数");
}

}