Java:如何将用户输入分配给数组

Question

所以我正在制作一个java程序，它接受客户购买的东西，并使用数组和 HashMap 来计算CSE作业的成本(也用它来打印其他东西)。但现在我希望用户能够首先输入产品，然后输入数量，以便能够制作一个简单的、用户友好的“收银机”程序。基本上只是想要 system.out 对如何做到这一点有什么想法吗？

不确定包含多个 Scanner/system.in 代码行的循环是否有效，而且我真的不确定如何解决这个问题。

哦，如果有人问类似的问题，请告诉我!我找不到类似的东西，但我可能错了。

import java.util.HashMap;
import java.util.ArrayList;
public class preLab3 {

// PreLab Q1: Compute the price of buying a specific quantity of a single item

    public static double getPriceSingleItemType(HashMap<String, Double> priceList, String itemType, int quantity) {
        double itemPrice = priceList.get(itemType);
        return itemPrice * quantity;
    }


// PreLab Q2: Compute the price of a single order
    public static double getPrice(HashMap<String, Double> priceList, ArrayList<String> basket) {

        double totalCost = 0.0;
        for(String item: basket) {
            double itemPrice = priceList.get(item);
            totalCost = totalCost + itemPrice;
        }

        return totalCost;
    }


public static HashMap<String, Double> getPriceList() {
    HashMap<String, Double> priceList = new HashMap<String, Double>();

    priceList.put("eggs", 1.79); // per dozen
    priceList.put("butter", 3.19);
    priceList.put("cheese", 5.99);
    priceList.put("apple", 0.99); // per pound
    priceList.put("banana", 0.39); // per pound
    priceList.put("strawberries", 1.99);
    priceList.put("peppers", 0.99);
    priceList.put("tomato sauce", 0.5);
    priceList.put("chocolate chips", 2.29);

    return priceList;
}
public static void main(String[] args) {

    System.out.println(getPriceList());

// PreLab Q3: I want to buy 3 lbs of strawberries
    double price = getPriceSingleItemType(getPriceList(), "strawberries", 3);
    System.out.println(price);

    ArrayList<String> cart = new ArrayList<>();

    cart.add("strawberries");
    cart.add("strawberries");
    cart.add("strawberries");
    cart.add("chocolate chips");
    cart.add("banana");
    cart.add("banana");
    cart.add("apple");
    cart.add("eggs");
    cart.add("butter");

    double totalCost = getPrice(getPriceList(), cart);
    System.out.println("The customer must pay: " + totalCost + " USD");

    ArrayList<HashMap<String, Integer>> orders = new ArrayList<>();
    for(HashMap<String, Integer> maps : orders) {


    }
}

}

Answer 1

首先创建一个Scanner用于用户输入的对象，然后使用您已获得的示例代码，其中 cart.add(item) 添加用户输入 item，并循环每个项目以获取用户输入 quantity。总的来说是这样的:

// ... same code above   
ArrayList<String> cart = new ArrayList<>();

Scanner input = new Scanner(System.in);
String user_item = "";
int user_quantity = 0;
System.out.println("What items would you like to buy?");

// Loop to repeatedly get user input and add items to cart
// until user enters "q" for item to quit.
do {
    System.out.print("Item? (q to quit) ");
    user_item = input.nextLine();
    if (user_item.equals("q")){
        break;
    }
    System.out.print("How many " + user_item + "? ");
    user_quantity = input.nextInt();
    System.out.println(user_quantity + " " + user_item);
    for(int q = 0; q <= user_quantity; q++){
       cart.add(user_item);
    }
} while(!input.nextLine().equals("q"));
input.close();

// Remove these
// cart.add("strawberries");
// cart.add("strawberries");
// cart.add("strawberries");
// cart.add("chocolate chips");
// cart.add("banana");
// cart.add("banana");
// cart.add("apple");
// cart.add("eggs");
// cart.add("butter");

double totalCost = getPrice(getPriceList(), cart);
// ... same code below

运行示例:

{banana=0.39, eggs=1.79, apple=0.99, butter=3.19, peppers=0.99, chocolate chips=2.29, tomato sauce=0.5, strawberries=1.99, cheese=5.99}
What items would you like to buy?
Item? (q to quit) butter
How many butter? 1
1 butter
Item? (q to quit) eggs
How many eggs? 2
2 eggs
Item? (q to quit) q
The customer must pay: 11.75 USD

当然，您可能还想为无效的用户输入添加错误/异常处理。

希望这有帮助。