Java中arraylist中的arraylist

Question

我必须创建一个 Shops 对象的数组列表，其中包含名称、描述和另一个产品对象的数组列表。 addProduct 方法留空，因为这是我面临的问题。我需要在使用 Shops 对象创建的商店数组列表中选择一个特定的商店名称，然后在产品数组列表中添加一个或多个产品。我不明白我怎么能做到这一点。如果你们能帮助我。

这是我目前的代码：

//class of shops but I removed the getters and setters to keep the code short
public class Shops {
    private  String name;
    private String desc;
    private ArrayList<Products> product;

    public Shops(String name, String desc, ArrayList<Products> product) {
        this.name = name;
        this.desc = desc;
        this.product = product;
    }

//another class called Shop assistant which adds products to a specific shop

 public class ShopAssistant {

   ArrayList<Shops> shop = new ArrayList<>();

public void addShops(Shops shop) {
    shop.add(shop);
}
public void addProduct(Products product ) {
    //add products to product arraylist which should be linked to shop arraylist
}

Answer 1

您必须知道在哪里添加产品。您必须将其添加到 ArrayList 内的 Shop 对象，而不是 ArrayList。您可以通过它在 ArrayList 中的索引来获取商店，因此您可能需要另一个 int 参数。

Answer 2

您首先需要将 'addProduct' 方法放在 'Shop' 类中，以便将产品添加到商店的数组列表中。

然后，您可以在“ShopAssistant”类中创建诸如“addProductToShop”之类的方法，该方法获取商店和产品，并将产品添加到商店，例如使用 for 循环查找商店，并使用 'Shop' 类中的 'addProduct' 方法添加产品。

我还建议将“shop”重命名为“shops”，将“product”重命名为“products”，以便更清楚地了解它们的含义。

Answer 3

public class Shop {
    private String name; 
    private String description;
    private ArrayList<Products> products;

    public Shop(String name, String description, ArrayList<Products>products){
        this.name = name; 
        this.description = description;
        this.products = products;
    }

    //This is the main issue that you were missing. 
    //You need to have addProducts in both the shop and assistant. 
    public void addProducts(ArrayList<Products>newProducts){
        newProducts.forEach((product) -> {
            this.products.add(product);
        });
    }
}

public class ShopAssistant {
    ArrayList<Shop> shops = new ArrayList<>();
    public void addShop(Shop newShop){
        shops.add(newShop);
    }

    //Call AddProducts for each shop in the list of shops that need products updated.
    public void addProducts(ArrayList<Products>newProducts, ArrayList<Shop>shopsToAddTo){
        shopsToAddTo.forEach((shop) -> {
            shop.addProducts(newProducts);
        });
    }
}