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I have to create an arraylist of Shops objects which have a name, description and another arraylist of products objects. The addProduct method is left blank because this is where I face a problem. I need to select a specific shop name in the shop arraylist created with Shops objects and then add one or more products in the arraylist of products. I don't understand how I can manage to do that. If you guys could help me.

This is the code I have so far:

//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
}
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    I would consider this a bad design. The Shop ought to provide an API for maintaining its List of Products. Commented Oct 9, 2018 at 14:54

3 Answers 3

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You have to know where to add the product. You have to add it to a Shop object inside the ArrayList, not to the ArrayList. You can get a shop by its index in the ArrayList, so you probably need another int parameter.

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Comments

1

You first need the 'addProduct' method to be in the 'Shop' class, to add a product to the shop's arraylist.

Then, you can create a method such as 'addProductToShop' in the 'ShopAssistant' class that takes a shop and a product, and adds the product to the shop e.g. use a for-loop to find the shop, and add the product using the 'addProduct' method from the 'Shop' class.

I would also advise renaming 'shop' to 'shops' and 'product' to 'products' to make it more clear what they hold.

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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);
        });
    }
}
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4 Comments

Something like this should work. Didn't have time to test it though so don't get upset if there are some bugs. You will just need to generate the list of shops that need to have the product added. You could do this by setting up an ArrayList of Shops in your main class and then loop through and find shops by name or description etc.
The thing is that I am not sure how to add a products arraylist of specific products to an arraylist of shops with a specific name. I have to take a string name from the user for the Shop name and then compare it to an existing shop name and then add the products. This is where I am stuck. Because I do not know how to compare a given name with the existing Shop names and add the specific products only to that shop of the arraylist.
Are you just taking in data from the console or are you reading from a file? Either way once you have the list of names of shops you can loop through your ArrayList of shops and check if the names match. Otherwise if you are not required to use array lists you could use a key value map to store your shops in and then just get the shops by name and add the products.
Do you have an example of the format that you are reading your data from?

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