Question

我目前正在完成一个简单的票务系统的作业，但对于如何正确计算循环我感到困惑。

基本上，该程序将计算在本地电影院购买门票的总费用，但是，当用户输入特定的TicketType和数量时，循环将重置，用户将输入第二个TicketType和数量，并且此过程将重复多次，直到用户切下循环为止，并显示所有循环的总计算成本。

我在这里和亲自获得了代码方面的帮助，而对于为什么此循环未正确循环，我感到很困惑！单个循环计算完美，但是第二个循环失败。

我目前正在尝试使用枚举类，该类已协助解决票务计算中的其他问题。

package ticketingsystem

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;


public class ticketingsystem {

    /**
     *
     * @param args
     * @throws IOException
     */
    public static void main(String[] args) throws IOException {

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    String order, again;
    int quantity = 0;
    double totalPrice;
        totalPrice = 0;
    TicketType ticketType;

    System.out.println("  ");

    System.out.println("Welcome to the cinemas!");

    System.out.println(" ");
    System.out.println("MAIN MENU");
    System.out.println(" ");
    System.out.println("The cinema has the following options");
    System.out.println(" ");
    System.out.println("1 = Child (4-5 yrs)");
    System.out.println("2 = Adult (18+ yrs)");
    System.out.println("3 = Senior (60+ yrs)");

    do {
      System.out.println(" ");
      System.out.print("Enter your option: ");
      order = br.readLine();

      switch (order.toLowerCase()) {
        case "1":
          ticketType = TicketType.child;
          break;

        case "3":
          ticketType = TicketType.senior;
          break;

        default:
          ticketType = TicketType.adult;
          break;
      }

      System.out.print("Enter the number of tickets: ");
      quantity = Integer.parseInt(br.readLine());

      totalPrice += ticketType.getPrice() * quantity;
      System.out.printf("You are purchasing %s tickets at %.2f \n", ticketType, ticketType.getPrice());

      System.out.print("Do you wish to continue?  (Y/N) : ");
      again = br.readLine(); 
    }
    while (again.equalsIgnoreCase("y"));

    System.out.println(" ");
    System.out.printf("Total Price           : $%.2f \n", totalPrice);
  }
}

我也将门票价格链接到枚举类，详细信息如下：

package ticketingsystem;

/**
 *
 * @author 
 */
enum TicketType {
    child(18), adult(36), senior(32.5);

    TicketType(double price) {
        this.price = price;
    }

    private double price;

    public double getPrice() {
        return price;
    }
}

期望的输出是要重复无数次的循环，同时保留先前计算出的数字，只要用户需要就可以。

没有错误消息，但是在第二个循环中输入票证类型和数量后，系统没有输出。

Answer 1

FWIW，我也刚刚尝试了您最初发布的问题中的代码。

您问题中的代码唯一的错误是在public class ticketingsystem主类的package语句中缺少分号。

这是一个错误，这意味着编译时它会失败并且仅运行代码的先前版本。这可能就是为什么您没有获得预期的结果（您正在运行旧版本）的原因。

这是我使用您确切的代码的会话记录（在主类的package语句上加上分号）：

Welcome to the cinemas!

MAIN MENU

The cinema has the following options

1 = Child (4-5 yrs)
2 = Adult (18+ yrs)
3 = Senior (60+ yrs)

Enter your option: 1
Enter the number of tickets: 2
You are purchasing child tickets at 18.00 
Do you wish to continue?  (Y/N) : y

Enter your option: 2
Enter the number of tickets: 3
You are purchasing adult tickets at 36.00 
Do you wish to continue?  (Y/N) : n

Total Price           : $144.00

昂贵的电影院！

FWIW，正如R. Katnaan所说，您必须遵循语法规则。但是，枚举元素名称的大写字母不是该语言的规则。这是一个高度提倡的约定（编码标准）。我同意您应该对您的枚举元素使用大写字母，但这并不是您遇到问题时破坏代码的地方...

如果遵循该编码约定，则还应该将Capital CamelCase用于类（接口和枚举名称）及其他。例如，使用public class TicketingSystem而不是public class ticketingsystem。以下是一些有关命名约定的指南。请记住，这些是指南，而不是编译器强制执行的规则：

这些约定很重要，因为它们为您的代码读者提供了一些有关它们可能正在寻找的线索。例如，如果我看到x = SOME_VALUE;，我将假定x被分配一个常量，而不是x = someValue;，我将假定x被分配了另一个变量的值。等等...

Answer 2

运行它时，我似乎没有在您的代码中发现任何问题。当我运行您的代码时，请参见下面的输出，它计算得很好：

Welcome to the cinemas!

MAIN MENU

The cinema has the following options

1 = Child (4-5 yrs)
2 = Adult (18+ yrs)
3 = Senior (60+ yrs)

Enter your option: 2
Enter the number of tickets: 2
You are purchasing adult tickets at 36.00 
Do you wish to continue?  (Y/N) : Y

Enter your option: 3
Enter the number of tickets: 1
You are purchasing senior tickets at 32.50 
Do you wish to continue?  (Y/N) : Y

Enter your option: 1
Enter the number of tickets: 1
You are purchasing child tickets at 18.00 
Do you wish to continue?  (Y/N) : N

Total Price           : $122.50

Answer 3

当我尝试使用以下代码时，一切正常。

package mm.com.java.so.test;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class TicketingSystem {

    enum TicketType {

        CHILD(18), ADULT(36), SENIOR(32.5);

        TicketType(double price) {
            this.price = price;
        }

        private double price;

        public double getPrice() {
            return price;
        }
    }

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

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        String type, again;
        int quantity = 0;
        double totalPrice = 0;
        TicketType ticketType;

        System.out.println("Welcome to the cinemas!\n");

        System.out.println("MAIN MENU\n");
        System.out.println("The cinema has the following options\n");
        System.out.println("1 = Child (4-5 yrs)");
        System.out.println("2 = Adult (18+ yrs)");
        System.out.println("3 = Senior (60+ yrs)");

        do {

            System.out.print("\nEnter your option: ");

            type = br.readLine();

            switch (type) {
                case "1":
                    ticketType = TicketType.CHILD;
                    break;

                case "2":
                    ticketType = TicketType.ADULT;
                    break;

                default:
                    ticketType = TicketType.SENIOR;
                    break;
            }

            System.out.print("Enter the number of tickets: ");

            quantity = Integer.parseInt(br.readLine());

            totalPrice += ticketType.getPrice() * quantity;

            System.out.printf("--> You are purchasing %s - %s Ticket(s) at $%s\n", quantity, ticketType, ticketType.getPrice());

            System.out.print("\nDo you wish to continue?  (Y/N) : ");

            again = br.readLine();

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

        System.out.printf("\n==> Total Price : $%s \n", totalPrice);
    }
}

您可以在这里查看我的测试结果。

Welcome to the cinemas!

MAIN MENU

The cinema has the following options

1 = Child (4-5 yrs)
2 = Adult (18+ yrs)
3 = Senior (60+ yrs)

Enter your option: 1
Enter the number of tickets: 1
--> You are purchasing 1 - CHILD Ticket(s) at $18.0

Do you wish to continue?  (Y/N) : y

Enter your option: 2
Enter the number of tickets: 2
--> You are purchasing 2 - ADULT Ticket(s) at $36.0

Do you wish to continue?  (Y/N) : y

Enter your option: 3
Enter the number of tickets: 3
--> You are purchasing 3 - SENIOR Ticket(s) at $32.5

Do you wish to continue?  (Y/N) : n

==> Total Price : $187.5

注意::如果您是JAVA开发人员，则在编写代码时（例如类名）必须遵循JAVA规则和规定。我格式化了您的代码。请仔细检查。

此代码在我的PC上正常运行。

无法正确计算循环

3 个答案: