为什么不输入直接按回车会出现错误

在转化int之前加个判断

import java.util.Scanner;
public class Main {
public static void main(String[] args){
Scanner in = new Scanner(System.in);
String[] num = null;
num = in.nextLine().split(" ");

    if (num[0].equals("")) {
        System.out.println("#Total:0");
    } else {
        int[] number = new int[num.length];
        for(int i= 0;i<number.length;i++){
            number[i]= Integer.valueOf(num[i]);
        }
        System.out.println("#Total:" + number.length);
    }
}
}