使用java写一个商城的程序

下面是一个简单的商城程序的示例代码：

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

class Product {
    private String name;
    private double price;

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

    public String getName() {
        return name;
    }

    public double getPrice() {
        return price;
    }
}

class ShoppingCart {
    private List<Product> items;

    public ShoppingCart() {
        items = new ArrayList<>();
    }

    public void addItem(Product product) {
        items.add(product);
    }

    public void removeItem(Product product) {
        items.remove(product);
    }

    public double calculateTotalPrice() {
        double total = 0;
        for (Product item : items) {
            total += item.getPrice();
        }
        return total;
    }
}

public class Shop {
    private List<Product> products;
    private ShoppingCart cart;

    public Shop() {
        products = new ArrayList<>();
        cart = new ShoppingCart();
    }

    public void addProduct(Product product) {
        products.add(product);
    }

    public void removeProduct(Product product) {
        products.remove(product);
    }

    public void displayProducts() {
        System.out.println("Available products:");
        for (int i = 0; i < products.size(); i++) {
            Product product = products.get(i);
            System.out.println((i + 1) + ". " + product.getName() + " - $" + product.getPrice());
        }
    }

    public void addToCart(int productIndex) {
        if (productIndex >= 1 && productIndex <= products.size()) {
            Product selectedProduct = products.get(productIndex - 1);
            cart.addItem(selectedProduct);
            System.out.println(selectedProduct.getName() + " added to cart.");
        } else {
            System.out.println("Invalid product index.");
        }
    }

    public void removeFromCart(int productIndex) {
        if (productIndex >= 1 && productIndex <= cart.getItems().size()) {
            Product selectedProduct = cart.getItems().get(productIndex - 1);
            cart.removeItem(selectedProduct);
            System.out.println(selectedProduct.getName() + " removed from cart.");
        } else {
            System.out.println("Invalid product index.");
        }
    }

    public void displayCart() {
        List<Product> items = cart.getItems();
        if (items.size() == 0) {
            System.out.println("Cart is empty.");
        } else {
            System.out.println("Cart:");
            for (int i = 0; i < items.size(); i++) {
                Product product = items.get(i);
                System.out.println((i + 1) + ". " + product.getName() + " - $" + product.getPrice());
            }
            System.out.println("Total: $" + cart.calculateTotalPrice());
        }
    }

    public static void main(String[] args) {
        Shop shop = new Shop();
        shop.addProduct(new Product("Product 1", 10.0));
        shop.addProduct(new Product("Product 2", 20.0));
        shop.addProduct(new Product("Product 3", 30.0));

        Scanner scanner = new Scanner(System.in);
        int choice;

        do {
            System.out.println("1. Display products");
            System.out.println("2. Add to cart");
            System.out.println("3. Remove from cart");
            System.out.println("4. Display cart");
            System.out.println("0. Exit");
            System.out.print("Enter your choice: ");
            choice = scanner.nextInt();

            switch (choice) {
                case 1:
                    shop.displayProducts();
                    break;
                case 2:
                    System.out.print("Enter the product index to add to cart: ");
                    int productIndex = scanner.nextInt();
                    shop.addToCart(productIndex);
                    break;
                case 3:
                    System.out.print("Enter the product index to remove from cart: ");
                    productIndex = scanner.nextInt();
                    shop.removeFromCart(productIndex);
                    break;
                case 4:
                    shop.displayCart();
                    break;
                case 0:
                    System.out.println("Exiting...");
                    break;
                default:
                    System.out.println("Invalid choice.");
            }
        } while (choice != 0);
    }
}

这个程序使用了面向对象的思想，定义了Product类和ShoppingCart类来表示商品和购物车，Shop类作为商店的主类。程序通过命令行菜单提供了显示商品、添加商品到购物车、从购物车中移除商品和显示购物车等功能。

在main方法中，我们创建了一个Shop实例，然后添加了一些商品。然后，程序会进入一个循环，根据用户的选择执行相应的操作，直到用户选择退出。

你可以根据自己的需求对代码进行修改和扩展