防止增量器关闭带有有效输入的程序

Question

我制作了一个可以编译和运行的货币转换器，但其目的之一是允许最多 3 次尝试输入要转换的正确货币类型。我在第三次尝试时遇到的问题，无论用户输入是否正确（字符“Y”、“y”、“P”或“p”），程序仍然关闭。如何解决此问题，以便仅在输入不正确的字符时才在第三次尝试时关闭？

public class CurrencyConverter 
{

  public static void main(String[] args) throws IOException
  {

    //Store these 2 conversion rate as constant (final) variables
    final double PESO = 20.37, YEN = 114.37;
    //initialize variable for the converted currency
    double total = 0;

    char type; //currency type
    char decision = 'Y'; //variable for user decision to re-run program
    int attempt = 1; //initializing attempts variable to increment attempts

    //Get the data from the user
    Scanner k = new Scanner(System.in);

    do
    {
      //boolean statement for while loop
      boolean input = false;
      //Get the amount of USD
      System.out.println("how much money do you want to convert?");
      double usd = k.nextDouble();

      //Get the conversion type (peso or yen)
      System.out.println("do you want to convert to Peso or Yen?");
      type = k.next().charAt(0); //get first character of whatever user types

      while((!input) && (attempt != 3))
      {
        switch(type)
        {
          case 'p':
          case 'P':
            input = true;
            //convert and print
            total = usd * PESO;
            System.out.printf("$%.2f = %.2f Peso\n", usd, total);
            break;
          case 'y':
          case 'Y':
            input = true;
            //convert and print
            total = usd * YEN;
            //System.out.printf("$" + usd + " = " + total + " Yen"); no formatting
            System.out.printf("$%.2f = %.2f Yen\n", usd, total);
            break;
          default:
            System.out.println("Sorry Invalid Currency type, please try again");
            System.out.println("do you want to convert to Peso or Yen?");
            type = k.next().charAt(0);
            //increment attempt
            attempt++;
            //close program after 3 failed attempts
            if(attempt == 3)
            {
              System.out.print("Too many failed attempts, goodbye!");
              System.exit(1);
            }
        }
        //if-else-if statement
        if ((usd >= 1000) && (type=='p' || type=='P'))
        {
          System.out.println("You're going to have a blast in Mexico");
        }
        else if ((usd > 5000) && (type=='y' || type=='Y'))
        {
          System.out.println("Have a great time in Japan!");
        }
        else if (usd < 10)
        {
          System.out.println("Haha you're broke!");
        }     
      }
      System.out.print("Would you like to re-run the program? (Y=yes, N=no)");
      decision = k.next().charAt(0);
    }while((decision == 'Y') || (decision == 'y'));

    FileWriter fw = new FileWriter("output.txt", true);
    PrintWriter pw = new PrintWriter(fw);     
    pw.println(total);
    pw.println(type);
    pw.close();

    k.close();
  }

}

Answer 1

在您的 if 尝试中，您可以添加验证，如果 if 与 'Y'、'y'、'P' 或 'p' 不同，则将继续退出程序。

 if(attempt == 3 && type != 'y' && type!='Y' && type!='p' && type!='P')
                        {
                            System.out.print("Too many failed attempts, goodbye!");
                            System.exit(1);
                        }