java - 通过读取文件创建对象，该对象也具有动态数组作为其字段

Question

我有一个包含购买信息的文本文件，其结构如下

客户名称 tab 成员(member)类型 tab 购物日期 tab 产品名称 tab 数量 换行

客户可以一次购买多个不同的对象，因此 ProductName 和 Quantity 可以像这样出现多次

Mary    gold    26.01.2020  Sweater 1   Jeans   2
Eve silver  20.02.2020  Sweater 2   Jeans   1
Steve   bronze  19.01.2020  Jeans   2   Sweater 3

我目前正在尝试从这些数据创建客户对象，这是我的实现

import java.io.File;
import java.io.FileNotFoundException;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) throws FileNotFoundException, ParseException {
        Scanner shoppingList = new Scanner(new File("shoppingList.txt");
        shoppingList.useDelimiter("[\t\n]");

        Customer[] customers = new Customer[0];
        while (shoppingList.hasNext()) {
            String customerName = shoppingList.next();
            String customerMembershipType = shoppingList.next();
            String purchaseDate = shoppingList.next();

            SimpleDateFormat formatter = new SimpleDateFormat("dd.MM.yyyy");
            Date date = formatter.parse(purchaseDate);

            String[] productNameList = new String[0];
            int[] quantityList = new int[0];
            while (shoppingList.hasNext()) {
               //this is where i stuck 
            }
            Customer[] newCustomer = new Customer(customerName, customerMembershipType, purchaseDate, productNameList, quantityList);
            customers = addCustomer(customers, newCustomer);
        }
    }

        private static Customer[] addCustomer(Customer[] customers, Customer customerToAdd) {
        Customer[] newCustomers = new Customer[customers.length + 1];
        System.arraycopy(customers, 0, newCustomers, 0, customers.length);
        newCustomers[newCustomers.length - 1] = customerToAdd;
        return  newCustomers;
    }

    static class Customer {
        protected String customerName;
        protected String customerMembershipType;
        protected Date purchaseDate;
        protected String[] productNameList;
        protected int[] quantityList;

        public Customer(String customerName, String customerMembershipType, Date purchaseDate, String[] productNameList, int[] quantityList) {
            this.customerName = customerName;
            this.customerMembershipType = customerMembershipType;
            this.purchaseDate = purchaseDate;
            this.productNameList = productNameList;
            this.quantityList = quantityList;  
    }
}

基本上，我想创建可以保存产品名称列表及其数量列表的 Customer 对象，但由于数组是不可变的，并且客户可以购买无限数量的产品类型，如果不使用 arrayLists，我无法找到解决方案，但是我无法在这个作业。此时我能做什么？

Answer 1

我建议您不要尝试读取客户行并解析这些行，而是单独进行操作，即将行作为行读取，每个客户一行，然后根据您的逻辑解析行。

如下所示(请注意，我更改了客户表示，并且客户现在是列表而不是数组):

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.*;

public class Main {
    public static void main(String[] args) throws IOException, ParseException {
        BufferedReader reader = new BufferedReader(new FileReader(new File("shoppingList.txt")));

        List<Customer> customers = new ArrayList<>();
        for (String line = reader.readLine(); line != null; line = reader.readLine()) {
            Scanner shoppingList = new Scanner(line);
            String customerName = shoppingList.next();
            String customerMembershipType = shoppingList.next();
            String purchaseDate = shoppingList.next();

            SimpleDateFormat formatter = new SimpleDateFormat("dd.MM.yyyy");
            Date date = formatter.parse(purchaseDate);

            Customer customer = new Customer(customerName, customerMembershipType, date);

            while (shoppingList.hasNext()) {
                customer.addProduct(shoppingList.next(), shoppingList.nextInt());
            }
        }
    }

    static class Customer {
        protected String customerName;
        protected String customerMembershipType;
        protected Date purchaseDate;
        protected Map<String, Integer> products = new HashMap<>();

        public Customer(String customerName, String customerMembershipType, Date purchaseDate) {
            this.customerName = customerName;
            this.customerMembershipType = customerMembershipType;
            this.purchaseDate = purchaseDate;
        }

        public void addProduct(String name, int qty) {
            products.put(name, qty);
        }
    }
}