如何实现购物车数量提醒功能的Java开关买菜系统

public class ShoppingCart {
    private String itemName;
    private double price;
    private int quantity;
    
    // 构造函数
    public ShoppingCart(String itemName, double price, int quantity) {
        this.itemName = itemName;
        this.price = price;
        this.quantity = quantity;
    }
    
    // 获取购物车中的商品数量
    public int getQuantity() {
        return quantity;
    }
    
    // 显示购物车中的商品信息
    public void displayItemInfo() {
        System.out.println("商品名称：" + itemName);
        System.out.println("商品价格：" + price);
        System.out.println("商品数量：" + quantity);
    }
}

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

public class Main {
    public static void main(String[] args) {
        ArrayList<ShoppingCart> shoppingCartList = new ArrayList<>();
        Scanner scanner = new Scanner(System.in);
        
        System.out.println("欢迎使用购物车系统！");
        
        while (true) {
            System.out.println("请选择操作：");
            System.out.println("1. 添加商品到购物车");
            System.out.println("2. 查看购物车中的商品数量");
            System.out.println("3. 退出系统");
            
            int choice = scanner.nextInt();
            
            if (choice == 1) {
                System.out.println("请输入商品名称：");
                String itemName = scanner.next();
                
                System.out.println("请输入商品价格：");
                double price = scanner.nextDouble();
                
                System.out.println("请输入商品数量：");
                int quantity = scanner.nextInt();
                
                ShoppingCart shoppingCart = new ShoppingCart(itemName, price, quantity);
                shoppingCartList.add(shoppingCart);
                
                System.out.println("已成功添加商品到购物车！");
            } else if (choice == 2) {
                int totalQuantity = 0;
                for (ShoppingCart cart : shoppingCartList) {
                    totalQuantity += cart.getQuantity();
                }
                
                System.out.println("购物车中的商品数量为：" + totalQuantity);
            } else if (choice == 3) {
                System.out.println("感谢使用购物车系统，再见！");
                break;
            } else {
                System.out.println("输入无效，请重新选择操作！");
            }
        }
        
        scanner.close();
    }
}