Java 菜单在输入后显示两次

Question

嘿伙计们，在过去的几个小时里，我一直在为课堂上研究这个程序，但似乎无法解决最后两个问题。它基本上是一个略微修改的CashRegister类，通过菜单具有基本功能。我遇到的问题是：

1(用户第一次选择菜单后，每次菜单都会在控制台中显示两次，我似乎找不到解决此问题的方法。

2(此外，每当我选择显示收银机的内容时，无论输入如何，第一行始终输出为0.00。

这是我的收银机课程，然后是我的测试人员：

import java.util.ArrayList;

/** * */

/** @author科尔 * */公共类收银机 {

   private double dailyTotal;
   private double totalPrice;
   ArrayList<Double> items;
   /**
      Constructs a cash register with cleared item count and total.
   */
   public CashRegister()
   {
      items = new ArrayList<Double>();
      dailyTotal = 0;
      totalPrice= 0;
   }
   /**
      Adds an item to this cash register.
      @param price the price of this item
   */
   public void addItem(double price)
   {
     items.add(price);
     dailyTotal = dailyTotal + price;
   }
   /**
      Gets the price of all items in the current sale.
      @return the total amount
   */
   public double getTotal()
   {
       for(int x=0; x<items.size(); x++){
          totalPrice = totalPrice + items.get(x);
      }

       return totalPrice;
   }
   /**
      Gets the number of items in the current sale.
      @return the item count
   */
   public int getCount()
   {
      return items.size(); 
   }
   /**
      Clears the item count and the total.
   */
   public void clear()
   {
      items.clear();
      totalPrice = 0;
   }
   public void display(){
       for(int x=0; x<items.size(); x++){
           System.out.printf("%10.2f%n", items.get(x));
       }
       System.out.println("------------------------------");
   }
   public double getDailyTotal(){
       dailyTotal = dailyTotal + totalPrice;
       return dailyTotal;

   }

}

import java.util.ArrayList;

import java.util.Scanner;

/** * */

/** @author科尔 * */公共类 Prog2 {

/**
 * @param args
 */
public static final String MENU = "******************************************n" +
              "* Enter "n" to start a new Cash Register.          *n" +
              "* Enter "a" to add an item to the current Cash Register.    *n" +
              "* Enter "d" to display the total of the current Cash Register.    *n" +
              "* Enter "e" to exit the program.   *n" +
              "******************************************";
    public static final String NEW_CUSTOMER = "n";
    public static final String ADD_ITEM = "a";
    public static final String DISPLAY = "d";
    public static final String EXIT = "e";

public static void main(String[] args) {
    // TODO Auto-generated method stub
    CashRegister register = new CashRegister();
    Scanner keyboard = new Scanner(System.in);
    String input;
    double userInput = 0;
    do {                                                
        input = printMenu(keyboard);                    

        if(input.equals(NEW_CUSTOMER)){
            register.getDailyTotal();
            register.clear();
        }
        else if(input.equals(ADD_ITEM)){
            System.out.println("Please enter the price of the item: ");
            register.addItem(userInput);
            userInput = keyboard.nextDouble();
        }
        else if(input.equalsIgnoreCase(DISPLAY)){
            register.display();
            System.out.println("Total: " + register.getTotal());
            System.out.println("Item Count: " +register.getCount());
        }

        else if(input.equalsIgnoreCase(EXIT)){
            System.out.printf("Daily Sales Total: " + "%.2f%n",register.getDailyTotal());
            System.out.println("Program Ended...");
            break;
            }
    }while(input != EXIT);
}
public static String printMenu(Scanner input){      //this method displays the menu for the user
    String response = "no reponse yet";
    System.out.println(MENU);
    response = input.nextLine();
    return response;        //response returned based on the users input
}

}

Answer 1

在添加项目之前，您需要从用户那里获得输入，这就是您为第一个项目获得 0 的原因。由于 userInput 的值在开始时设置为 0，并且语句已切换，因此您将始终初始化创建一个值为 0.0 的项目，所有其他值将比实际输入晚一步。

else if(input.equals(ADD_ITEM)){
     System.out.println("Please enter the price of the item: ");
     userInput = keyboard.nextDouble();
     register.addItem(userInput);    
}