简单模拟购物车

public class Goods {
    int id;
    String name;
    double price;
    int buyNumber;
}


public class ShopCar {
    public static void main(String[] args) {

        Goods[] shopCar = new Goods[100];

        while (true) {
            System.out.println("请输入以下命令进行操作");
            System.out.println("添加商品到购物车：add");
            System.out.println("查询购物车商品：query");
            System.out.println("修改商品购买数量：update");
            System.out.println("结算购买商品的金额：pay");

            Scanner sc = new Scanner(System.in);
            System.out.println("请输入命令");
            String command = sc.next();

            switch (command){
                case "add":
                    addGoods(shopCar, sc);
                    break;
                case "query":
                    queryGoods(shopCar);
                    break;
                case "update":
                    updateGoods(shopCar, sc);
                    break;
                case "pay":
                    payGoods(shopCar);
                    break;
                default:
                    System.out.println("命令错误请从新输入");
            }
        }
    }

    private static void payGoods(Goods[] shopCar) {
        //  先查出购买的索引商品
        queryGoods(shopCar);
        //  结算，定义一个总金额
        double money = 0.0;
        //  便利所有商品求和
        for (int i = 0; i < shopCar.length; i++) {
            Goods g = shopCar[i];
            if (g != null){
                money += (g.price * g.buyNumber);
            }else {
                System.out.println("没有想要购买的商品");
                break;
            }
        }
        System.out.println("商品总金额：" + money);
    }

    private static void updateGoods(Goods[] shopCar, Scanner sc) {
        //  修改商品信息
        while (true) {
            System.out.println("请输入需要修改的商品id：");
            int id = sc.nextInt();
            Goods g = getGoodsId(shopCar, id);
            if (g == null){
                System.out.println("该商品不存在请确认后在此输入");
            }else {
                //  商品存在进行修改
                System.out.println("请输入：" + g.name + "商品购买数量");
                int goodsNumber = sc.nextInt();
                System.out.println("请输入：" + g.name + "商品价格");
                double goodsPrice = sc.nextDouble();
                g.buyNumber = goodsNumber;
                g.price = goodsPrice;
                System.out.println("商品修改完成");
                queryGoods(shopCar);
                break;
            }
        }
    }
    private static Goods getGoodsId(Goods[] shopCar, int id) {
        //  获取商品id进行传输
        for (int i = 0; i < shopCar.length; i++) {
            Goods g = shopCar[i];
            if (g != null){
                if (g.id == id){
                    return g;
                }
            }else {
                return null;
            }
        }
        return null;
    }

    private static void queryGoods(Goods[] shopCar) {

        System.out.println("=========查询购物车=========");
        System.out.println("商品编号\t\t商品名称\t\t商品数量\t\t商品价格");

        for (int i = 0; i < shopCar.length; i++) {
            Goods g = shopCar[i];
            if (g != null){
                System.out.println(g.id + "\t\t\t" + g.name + "\t\t\t" + g.buyNumber + "\t\t\t" + g.price);
            }
        }
    }

    private static void addGoods(Goods[] shopCar, Scanner sc) {
        //  录入购买信息
        System.out.println("请输入购买商品编号（不重复）：");
        int id = sc.nextInt();
        System.out.println("请输入购买商品的名称：");
        String name = sc.next();
        System.out.println("请输入购买商品的数量：");
        int buyNumber = sc.nextInt();
        System.out.println("请输入购买商品的价格：");
        double price = sc.nextDouble();

        //  购买商品信息封装成对象
        Goods g = new Goods();
        g.id = id;
        g.name = name;
        g.buyNumber = buyNumber;
        g.price = price;

        //  将对象添加到购物车数组中
        for (int i = 0; i < shopCar.length; i++) {
            if (shopCar[i] == null){
                //  说明没有元素，将数据添加进去
                shopCar[i] = g;
                break;
            }
        }
        System.out.println("商品：" + g.name + "\t 添加购物车成功！");
    }
}