按照教材[案例7-8]的实现思路，在本实验第2题的基础上设计一个图书购物车，存储用户购买图书的信息。能够打印出购物车中图书的信息，图书价格、小计和总的费用。用HashMap类模拟购物车。 实现 （1）新建图书类（Product），该步骤第2题已实现。 （2）新建BookShop类，该类实现对所购图书信息的封装。 （3）新建书库类BookStore，书库里存放了大量的图书，这里我们用ArrayList来存放，并初始化部分图书信息。 （4）新建顾客类Customer。每个顾客进入书库都可以获得一个购物车，这个购物车用HashMap来实现，图书的编号是它的键,捆扎后的BookShop是它的值。 （5）新建测试主类SY6_3_BuyCar。

好的，根据您的要求，我编写了以下代码示例：

Product类：

public class Product {
    private String id; // 图书编号
    private String name; // 图书名称
    private double price; // 图书价格

    public Product(String id, String name, double price) {
        this.id = id;
        this.name = name;
        this.price = price;
    }

    public String getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public double getPrice() {
        return price;
    }
}

BookShop类：

public class BookShop {
    private Product product; // 所购图书
    private int quantity; // 数量

    public BookShop(Product product, int quantity) {
        this.product = product;
        this.quantity = quantity;
    }

    public Product getProduct() {
        return product;
    }

    public int getQuantity() {
        return quantity;
    }

    public double getSubtotal() {
        return product.getPrice() * quantity;
    }

    @Override
    public String toString() {
        return String.format("%-10s%-20s%-10.2f%-10d%-10.2f", 
                product.getId(), product.getName(), product.getPrice(), quantity, getSubtotal());
    }
}

BookStore类：

import java.util.ArrayList;
import java.util.List;

public class BookStore {
    private List<Product> products;

    public BookStore() {
        products = new ArrayList<>();
        products.add(new Product("001", "Java编程思想", 79.0));
        products.add(new Product("002", "Java核心技术", 89.0));
        products.add(new Product("003", "Java并发编程实战", 69.0));
    }

    public Product findProduct(String id) {
        for (Product product : products) {
            if (product.getId().equals(id)) {
                return product;
            }
        }
        return null;
    }
}

Customer类：

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Customer {
    private String name; // 顾客姓名
    private Map<String, BookShop> shoppingCart; // 购物车
    private BookStore bookStore; // 书库

    public Customer(String name, BookStore bookStore) {
        this.name = name;
        this.shoppingCart = new HashMap<>();
        this.bookStore = bookStore;
    }

    public void addBookToCart() {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入要购买的图书编号：");
        String id = scanner.nextLine();
        Product product = bookStore.findProduct(id);
        if (product == null) {
            System.out.println("该图书不存在！");
        } else {
            System.out.print("请输入购买数量：");
            int quantity = scanner.nextInt();
            scanner.nextLine();
            BookShop bookShop = shoppingCart.get(id);
            if (bookShop != null) {
                bookShop = new BookShop(product, bookShop.getQuantity() + quantity);
            } else {
                bookShop = new BookShop(product, quantity);
            }
            shoppingCart.put(id, bookShop);
            System.out.println("已将图书添加到购物车！");
        }
    }

    public void removeBookFromCart() {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入要删除的图书编号：");
        String id = scanner.nextLine();
        BookShop bookShop = shoppingCart.get(id);
        if (bookShop == null) {
            System.out.println("购物车中不存在该图书！");
        } else {
            shoppingCart.remove(id);
            System.out.println("已将图书从购物车中删除！");
        }
    }

    public void printShoppingCart() {
        System.out.println("===========================================");
        System.out.println("顾客姓名：" + name);
        System.out.println("购物车中的图书：");
        System.out.println("===========================================");
        System.out.printf("%-10s%-20s%-10s%-10s%-10s\n", "编号", "名称", "价格", "数量", "小计");
        System.out.println("-------------------------------------------");
        double totalCost = 0.0;
        for (BookShop bookShop : shoppingCart.values()) {
            System.out.println(bookShop);
            totalCost += bookShop.getSubtotal();
        }
        System.out.println("-------------------------------------------");
        System.out.printf("%-40s%-10.2f\n", "总费用：", totalCost);
        System.out.println("===========================================");
    }
}

SY6_3_BuyCar类：

public class SY6_3_BuyCar {
    public static void main(String[] args) {
        BookStore bookStore = new BookStore();
        Customer customer = new Customer("张三", bookStore);

        Scanner scanner = new Scanner(System.in);
        while (true) {
            System.out.println("请选择操作：");
            System.out.println("1. 添加图书到购物车");
            System.out.println("2. 从购物车中删除图书");
            System.out.println("3. 查看购物车");
            System.out.println("4. 退出系统");
            System.out.print("请输入操作编号：");
            int choice = scanner.nextInt();
            scanner.nextLine();
            switch (choice) {
                case 1:
                    customer.addBookToCart();
                    break;
                case 2:
                    customer.removeBookFromCart();
                    break;
                case 3:
                    customer.printShoppingCart();
                    break;
                case 4:
                    System.out.println("已退出系统！");
                    return;
                default:
                    System.out.println("无效操作，请重新输入！");
            }
        }
    }
}

希望能对您有所帮助！