用java写一个购物系统

购物系统可以分为以下几个部分：

1、商品类（Product）

2、购物车类（ShoppingCart）

3、用户类（User）

4、主程序（Main）

我们创建一个商品类（Product）：

public class Product {
    private int id;
    private String name;
    private double price;
    public Product(int id, String name, double price) {
        this.id = id;
        this.name = name;
        this.price = price;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public double getPrice() {
        return price;
    }
    public void setPrice(double price) {
        this.price = price;
    }
    @Override
    public String toString() {
        return "Product{" +
                "id=" + id +
                ", name='" + name + ''' +
                ", price=" + price +
                '}';
    }
}

接下来，我们创建一个购物车类（ShoppingCart）：

import java.util.ArrayList;
import java.util.List;
public class ShoppingCart {
    private List<Product> products;
    public ShoppingCart() {
        products = new ArrayList<>();
    }
    public void addProduct(Product product) {
        products.add(product);
    }
    public void removeProduct(Product product) {
        products.remove(product);
    }
    public double getTotalPrice() {
        double totalPrice = 0;
        for (Product product : products) {
            totalPrice += product.getPrice();
        }
        return totalPrice;
    }
    public void showCart() {
        System.out.println("购物车中的商品：");
        for (Product product : products) {
            System.out.println(product);
        }
        System.out.println("总价：" + getTotalPrice());
    }
}

我们创建一个用户类（User）：

public class User {
    private String username;
    private String password;
    private ShoppingCart shoppingCart;
    public User(String username, String password) {
        this.username = username;
        this.password = password;
        shoppingCart = new ShoppingCart();
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public ShoppingCart getShoppingCart() {
        return shoppingCart;
    }
}

我们创建一个主程序（Main）：

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        User user = new User("张三", "123456");
        Scanner scanner = new Scanner(System.in);
        boolean exit = false;
        while (!exit) {
            System.out.println("请选择操作：1.添加商品 2.删除商品 3.查看购物车 4.退出");
            int operation = scanner.nextInt();
            switch (operation) {
                case 1:
                    System.out.println("请输入商品ID：");
                    int productId = scanner.nextInt();
                    System.out.println("请输入商品名称：");
                    String productName = scanner.next();
                    System.out.println("请输入商品价格：");
                    double productPrice = scanner.nextDouble();
                    Product product = new Product(productId, productName, productPrice);
                    user.getShoppingCart().addProduct(product);
                    break;
                case 2:
                    System.out.println("请输入要删除的商品ID：");
                    int deleteProductId = scanner.nextInt();
                    Product deleteProduct = null;
                    for (Product p : user.getShoppingCart().getProducts()) {
                        if (p.getId() == deleteProductId) {
                            deleteProduct = p;
                            break;
                        }
                    }
                    if (deleteProduct != null) {
                        user.getShoppingCart().removeProduct(deleteProduct);
                    } else {
                        System.out.println("商品不存在！");
                    }
                    break;
                case 3:
                    user.getShoppingCart().showCart();
                    break;
                case 4:
                    exit = true;
                    break;
                default:
                    System.out.println("无效的操作，请重新选择！");
            }
        }
        scanner.close();
    }
}

这个简单的购物系统可以实现商品的添加、删除和查看购物车功能，你可以根据需要进一步完善和优化这个系统。