Java实现购物车功能_面向对象思维下的购物系统建模

public class Product {
    private final String id;
    private final String name;
    private final double price;
<pre class='brush:java;toolbar:false;'>public Product(String id, String name, double price) {
    this.id = id;
    this.name = name;
    this.price = price;
}

// getter方法
public String getId() { return id; }
public String getName() { return name; }
public double getPrice() { return price; }

@Override
public boolean equals(Object o) {
    if (this == o) return true;
    if (!(o instanceof Product)) return false;
    Product product = (Product) o;
    return id.equals(product.id);
}

@Override
public int hashCode() {
    return id.hashCode();
}

public class CartItem {
    private Product product;
    private int quantity;
<pre class='brush:java;toolbar:false;'>public CartItem(Product product, int quantity) {
    this.product = product;
    this.quantity = quantity;
}

public void setQuantity(int quantity) {
    if (quantity > 0) {
        this.quantity = quantity;
    }
}

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

public Product getProduct() {
    return product;
}

public int getQuantity() {
    return quantity;
}

import java.util.*;
<p>public class ShoppingCart {
private Map<String, CartItem> items;</p><pre class='brush:java;toolbar:false;'>public ShoppingCart() {
    this.items = new HashMap<>();
}

public void addProduct(Product product, int quantity) {
    if (quantity <= 0) return;

    if (items.containsKey(product.getId())) {
        CartItem item = items.get(product.getId());
        item.setQuantity(item.getQuantity() + quantity);
    } else {
        items.put(product.getId(), new CartItem(product, quantity));
    }
}

public void removeProduct(String productId) {
    items.remove(productId);
}

public void updateQuantity(String productId, int quantity) {
    CartItem item = items.get(productId);
    if (item != null) {
        if (quantity <= 0) {
            items.remove(productId);
        } else {
            item.setQuantity(quantity);
        }
    }
}

public double getTotalPrice() {
    return items.values().stream()
               .mapToDouble(CartItem::getSubtotal)
               .sum();
}

public void showItems() {
    for (CartItem item : items.values()) {
        System.out.printf("商品: %s, 单价: %.2f, 数量: %d, 小计: %.2f%n",
                item.getProduct().getName(),
                item.getProduct().getPrice(),
                item.getQuantity(),
                item.getSubtotal());
    }
    System.out.printf("总计: %.2f元%n", getTotalPrice());
}

public int getItemCount() {
    return items.size();
}

public boolean isEmpty() {
    return items.isEmpty();
}

public class Main {
    public static void main(String[] args) {
        Product p1 = new Product("P001", "iPhone", 6999.0);
        Product p2 = new Product("P002", "AirPods", 1299.0);
<pre class='brush:java;toolbar:false;'>    ShoppingCart cart = new ShoppingCart();
    cart.addProduct(p1, 1);
    cart.addProduct(p2, 2);
    cart.addProduct(p1, 1); // 合并

    cart.showItems();
    // 输出：
    // 商品: iPhone, 单价: 6999.00, 数量: 2, 小计: 13998.00
    // 商品: AirPods, 单价: 1299.00, 数量: 2, 小计: 2598.00
    // 总计: 16596.00元
}