java - 如何禁用除特定输入之外的键盘输入，或在使用错误的输入时显示错误？

Question

我是这个网站和一般编程的新手。我创建了一个小循环来尝试提高我对基础知识的理解。我想做的是最后用户输入“Y”或“N”，或者能够禁用这两个键中的每个键栏，确保我只得到这两个答案之一。如果这不可行，我会创建一个错误，然后循环回到问题，从而不会无意中停止程序。

非常感谢

   package com.company;


   import java.util.Scanner;

   public class Main {

   public static void main(String[] args) {

    Scanner scan = new Scanner(System.in);
    String answer = "y";

    do {

        System.out.println("Enter your number:");
        double originalNumber = scan.nextDouble();

        System.out.println("Calculating sum...");
        double modifyingNumber = (int) (Math.random() * ((100 - 0.5 + 10) + 3));
        double result = (originalNumber * modifyingNumber + 10d);

        if (result % 2 == 0) {

            System.out.println("Even- " + result);
        } else {

            System.out.println("Odd- " + result);
        }

        System.out.println("Random number was " + modifyingNumber);

        System.out.println("Would you like to try again? Y/N");
        answer = scan.next();

    } while (answer.equalsIgnoreCase("y"));

 }

}

Answer 1

添加另一个 do while 循环

do {

    System.out.println("Enter your number:");
    double originalNumber = scan.nextDouble();

    System.out.println("Calculating sum...");
    double modifyingNumber = (int) (Math.random() * ((100 - 0.5 + 10) + 3));
    double result = (originalNumber * modifyingNumber + 10d);

    if (result % 2 == 0) {

        System.out.println("Even- " + result);
    } else {

        System.out.println("Odd- " + result);
    }

    System.out.println("Random number was " + modifyingNumber);

    do {
        System.out.println("Would you like to try again? Y/N");
        answer = scan.next();
    } while(!answer.equalsIgnoreCase("y") && !answer.equalsIgnoreCase("n"));

} while (answer.equalsIgnoreCase("y"));