java - 跟踪价格和总成本

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我正在尝试跟踪每个项目的成本，并将其添加到所有项目的总成本中。当我运行程序时，最后一个项目成本和总成本将应用于每个项目。我觉得我应该有另一个循环更动态地放置每个项目的成本和总成本。

驱动程序类别:

    public class GroceryListTester
{
   public static void main(String[] args)
   {
       GroceryList get = new GroceryList();
       get.start();
   }
}

CheckMail 类:

import chn.util.*;
import java.util.*;

public class GroceryList
{
        //Instance variables
        private int myNumItems;
        private double myItemCost;
        private double myTotalCost;
        Scanner keyboard = new Scanner(System.in);

        //Constructor
        public GroceryList()
        {
            myNumItems = 0;
            myTotalCost = 0;
        }
        //Methods
        public void start()
        {
            System.out.print('\u000C');
            getMyNumItems();
            getMyItemPrices();
            output();
        }
        public int getMyNumItems()
        {
            System.out.print("How many items would you like to purchase? => ");
            myNumItems = keyboard.nextInt();

            return myNumItems;
        }
        public double getMyItemPrices()
        {
            int n = 0; //Disp item number

            while(n  < myNumItems)
            {
                System.out.print("Please enter price of item #" +(n+1) +": ");
                myItemCost = keyboard.nextDouble();
                myTotalCost = myTotalCost + myItemCost;
                ++n;
            }

            return myTotalCost;
        }
        public void output()
        {
            for(int n = 0; n < myNumItems; ++n)
            {
                System.out.println();
                System.out.printf("%8s %8s %8s", "Item #" +(n + 1) , "Cost: $" +myItemCost, "Total: $" +myTotalCost);

            }
        }
}

输出:

How many items would you like to purchase? => 3
Please enter price of item #1: 1.25
Please enter price of item #2: 1.75
Please enter price of item #3: 1.50

 Item #1 Cost: $1.5 Total: $4.5
 Item #2 Cost: $1.5 Total: $4.5
 Item #3 Cost: $1.5 Total: $4.5

Answer 1

问题是您没有存储除最后一项以外的任何商品价格的任何引用。这需要一个 ArrayList 来跟踪已订购的每个项目。

如果您没有使用 int myItemCost，而是使用了 ArrayList< int> myItemCosts，并且每次添加新商品时都将规定的价格添加到该列表中，则可以在最后打印每个商品。

这是一个例子:

ArrayList<int> myItemCosts = new ArrayList<int>();
public double getMyItemPrices()
{
    int n = 0;

    while (n < myNumItems)
    {
        System.out.print("Please enter price of item #" + (n+1) + ": ");
        myItemCosts.add(keyboard.nextDouble());
        myTotalCost += myItemCost;
    }
}

然后output()可以像这样构造:

public void output()
{
    for(int n = 0; n < myNumItems; ++n)
    {
        System.out.println();
        System.out.printf("%8s %8s %8s", "Item #" + (n + 1) , "Cost: $" + myItemCosts[n], "Total: $" + myTotalCost);
    }
 }

如果您决定需要向任何给定的杂货项目添加更多功能，例如 SKU、数量、折扣等，您应该创建自己的对象来封装这些属性:

class SampleGroceryItem
{
    public SampleGroceryItem(double price, int quantity, string sku, double discount)
    {
        this.Price = price;
        this.Quantity = quantity;
        this.Sku = sku;
        this.Discount = discount;
    }

    public double Price;
    public int Quantity;
    public string Sku;
    public double Discount;
}

然后每次用户输入所有必要信息时实例化一个新的 SampleGroceryItem，并将该对象添加到列表中。