import java.util.ArrayList; public class StockManager { // A list of the products. private ArrayList<Product> stock; /** * Initialise the stock manager. */ public StockManager() { stock = new ArrayList<>(); } /** * Add a product to the list. * @param item The item to be added. */ public void addProduct(Product item) { stock.add(item); } /** * Receive a delivery of a particular product. * Increase the quantity of the product by the given amount. * @param id The ID of the product. * @param amount The amount to increase the quantity by. */ public void delivery(int id, int amount) { } /** * Try to find a product in the stock with the given id. * @return The identified product, or null if there is none * with a matching ID. */ public Product findProduct(int id) { return null; } /** * Locate a product with the given ID, and return how * many of this item are in stock. If the ID does not * match any product, return zero. * @param id The ID of the product. * @return The quantity of the given product in stock. */ public int numberInStock(int id) { return 0; } /** * Print details of all the products. */ public void printProductDetails() { } }