基本OTP验证

Question

我如何验证使用扫描仪生成的otp？假设进行在线预订并生成OTP，并且在验证OTP之后，该项目就被预订了，即使我的NET也有问题，因为最后显示的总数为0。有什么方法可以在执行DEFAULT条件时将代码循环回“选择任何一个”？ 代码搞砸了

import java.util.Arrays;
import java.util.Scanner;
import java.util.Random;

public class Restaurant {

    static char[] otp(int len) {

        String numbers = "0123456789";

        Random rand = new Random();

        char[] otp = new char[len];
        for (int i = 0; i < len; i++) {

            otp[i] = numbers.charAt(rand.nextInt(numbers.length()));

        }
        return otp;
    }

    public static void main(String[] args) {
        int length = 4;

        Scanner sc = new Scanner(System.in);
        int net, total = 0, item;

        //gst = 18 / 100;
        String USEROTP;
        String Choice;
        System.out.println("Welcome to Restaurant");
        System.out.println("Todays menu is: ");
        System.out.println("1)Dosa\n2)Upma\n3)uttapaa");
        System.out.println("Choose any one [1-3]");
        item = sc.nextInt();

        switch (item) {
            case 1:

                System.out.println("You Picked up Dosa, which costs Rs: ");
                total += 70;
                System.out.println(total);
                System.out.println("Do you want to confirm ?");
                Choice = sc.next();
                if (Choice.equals("yes")) {
                    net = (int) (double) (total + (total + (0.18)));
                    System.out.println("generating otp");
                    System.out.println("Your OTP is given below");
                    System.out.println(otp(length));

                    //NEED TO VERIFY THE OTP HERE THEN BOOK THE ORDER

                    System.out.println("BOOKED SUCCESFULLY, your bill is: " + net);
                } else {

                    System.out.println("ok, visit next time");

                }
                break;

            case 2:
                net = (int) (double) (total + (total + (0.18)));
                System.out.println("You Picked up Upma, which cost Rs:");
                total += 50;
                System.out.println(total);
                System.out.println("Do you want to confirm ?");
                Choice = sc.next();
                if (Choice.equals("yes")) {
                    System.out.println("generating otp");
                    System.out.println("Your OTP is given below");
                    System.out.println(otp(length));

                  //NEED TO VERIFY THE OTP HERE THEN BOOK THE ORDER

                    System.out.println("BOOKED SUCCESFULLY, your bill is: " + net);
                } else {
                    System.out.println("ok, visit next time");
                }

                break;
            case 3:
                net = (int) (double) (total + (total + (0.18)));
                System.out.println("You Picked up uttapaa, which costs Rs:");
                total += 40;
                System.out.println(total);
                System.out.println("Do you want to confirm ?");
                Choice = sc.next();
                if (Choice.equals("yes")) {
                    System.out.println("generating otp");
                    System.out.println("Your OTP is given below");
                    System.out.println(otp(length));

                    //NEED TO VERIFY THE OTP HERE THEN BOOK THE ORDER

                    System.out.println("BOOKED SUCCESFULLY, your bill is: " + net);
                } else {
                    System.out.println("ok, visit next time");
                }
                break;
            default:
                System.out.println("Pick atleast one");

        }
    }

}