switch-if 给定9位数生成ISBN

package com.java.test;

import java.util.Scanner;

public class practice3_09 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter the first 9 digits of an ISBN as integer:");
        String s = sc.nextLine();
        //char[] arr =s.toCharArray();
        int[] num = new int[s.length()];
        for (int i = 0; i < num.length; i++) {
            num[i] = (int)s.charAt(i) - '0';
        }
        int sum = 0;
        for (int i = 0; i < num.length; i++) {
            sum += (i + 1)*num[i];
        }
        int d = sum % 11;
        if(d == 10) {
            System.out.println(s + "X");
        } else {
            System.out.println(s + d);
        }
    }

}