java - 使用 lambda 和流创建 buy_items 方法

Question

指令要求创建一个接受 Retail_item 对象作为参数的方法。每次调用purchaseItem方法时，作为参数传递的retail_item都应该添加到列表中。我已经有商店中的数据列表(列表)。我需要创建一个新列表，当用户从商店中选择一个选项时，它会创建一个新的购买项目列表。(这最终将在测试类中发生) 以下是我到目前为止所拥有的。我知道它不正确，但遇到很多麻烦。我对此很陌生。

public static void main(String[] args) {
        Cash_Register object = new Cash_Register(); 
            developerInfo();

            Retail_item[] items = {
                    new Retail_item(1000, "Pants", 10, 19.99),
                    new Retail_item(2000, "Jeans", 2, 25.95),
                    new Retail_item(3000, "Shirt", 12, 12.50),
                    new Retail_item(4000, "Dress", 3, 79.00),
                    new Retail_item(5000, "Socks", 50, 1.98),
                    new Retail_item(6000, "Sweater", 5, 49.99),
                    new Retail_item(7000, "Jacket", 1, 85.95),
                    new Retail_item(8000, "Suit", 2, 150.98),
                    new Retail_item(9000, "Swimsuit", 6, 44.50),
                    new Retail_item(9500, "Skirt", 4, 65.99)};

            List<Retail_item> list = Arrays.asList(items);
            object.displayMenu(list);
            object.purchaseItem(list); 


}
//display menu
    public void displayMenu(List<Retail_item> list) {
        System.out.println("Menu Items: ");
        System.out.println("");
        list.stream()
            .forEach(System.out::println);

    }
    //create a purchased item list for register
    public void purchaseItem(List<Retail_item> list) {
        List<List<Retail_item>> toList = Arrays.asList(list);

        toList.stream()
                .map(Retail_item-> new Cash_Register())
                .collect(Collectors.toList());              

    }

Answer 1

我不确定为什么你需要流。你的描述是这样的。

public void purchase_item( Retail_item item) {
        // the item list must exist somewhere, perhaps an instance field
        items.add(item);
}