Iain Ritchie

Hi Campbell, that’s a really useful tip. I have started writing my own programme of my own design to put this information into practice. And Junilu thanks for the recommendations, I have made a start on the book by Corey Haines although I am still following along with the programming course so will delve deeper into it once I have finished that

Hi Campbell, thank you for the welcome and the input. I have started to find myself looking at things differently now and take more consideration into the objects and relationships between them and hoping this will better inform my code. I appreciate the input from everyone and Stephen thank you for the suggestions I will start reading up and studying more source code as I think it would help demystify the workings of larger programmes.

Hi Carey and Junilu, thank you for the feedback it has been very valuable to me. I think I need to focus more on stepping back and taking more consideration with how to plan how things will work together rather than jump straight into the code and try to figure things out as I go which is resulting in me treating each class on its own rather than as part of a whole.  

Hello, This is my first post on this website so I'm not sure if it's good practice for me to upload as large a post as I have done. Currently I am following along with an online course to learn programming for Java 17. At the end of each section there are challenges to practice our understanding of the topics covered, the one I have just finished was about Java Collections. What I am finding hard with it is to get feedback on the code that I have wrote.
This challenge was the first where there wasn't as much hand holding and the only thing that was given were the class requirements and their methods and fields to create an Inventory System,  and it was up to us to figure out what type of collection to implement and how each method would function.
I was hoping to get some feedback on best practices, I'm not imagining anyone to go through everything line by line but if someone could maybe have a look at the odd bit and point out how they would have done things differently? One of the things I was most interested in was that I made the Cart class an inner class of the Store class and I'm not sure if this is good practice or not as I am struggling to understand the benefits of inner classes and not sure if they are used much so wanted to experiment to find a use for them and this made sense as the when the cart is instantiated it automatically adds itself to the list of Carts belonging to the Store.

Store import java.time.LocalDate; import java.util.*; public class Store {    private String storeName;    Map<String, InventoryItem> inventoryItemMap = new HashMap<>();    Map<Integer, Cart> carts = new HashMap<>();    Map<Category, Set<InventoryItem>> aisleInventory = new EnumMap<>(Category.class);    public class Cart {        private static int allId = 1;        private int id;        private Map<Product, Integer> products;        private int date;        private Type type;        public Cart(int date, Type type) {            this.id = allId++;            this.date = date;            this.type = type;            this.products = new HashMap<>();            carts.put(id, this);        }        public void addItem(String productName, int quantity){            InventoryItem item = inventoryItemMap.get(productName.toUpperCase());            if(item != null){                if(item.reserveItem(quantity)){                    if (products.computeIfPresent(item.product, (k, v) -> (v + quantity)) == null) {                        products.put(item.product, quantity);                    }                }            }        }        public void removeItem(String productName, int quantity) {            InventoryItem item = inventoryItemMap.get(productName.toUpperCase());            if(item == null) {                System.out.println("There is no : " + productName);                return;            }            if(products.containsKey(item.product)) {                int amountInCart = products.get(item.product);                int amountToRelease = (amountInCart < quantity) ? amountInCart : quantity;                item.releaseItem(amountToRelease);                products.computeIfPresent(item.product, (k, v) -> v - amountToRelease);                products.entrySet().removeIf(e -> e.getValue() <= 0);            } else {                System.out.println("You don't have any " + item.product.getName() + " in your cart");            }        }        public void printSalesSlip() {            System.out.printf("Your cart ID:%s%03d%n", (type == Type.VIRTUAL) ? "V" : "P", id);            products.forEach((k, v) -> {                InventoryItem item = inventoryItemMap.get(k.getName().toUpperCase());                System.out.printf("SKU:%-10s %-20s Quantity:%-10d Unit price:£%-10.2f total:£%-5.2f%n", k.getSku(), k.getName(), v,item.salesPrice , (v * item.salesPrice));            });            System.out.println("-".repeat(40));        }        public void releaseAll(){            products.forEach((k,v) -> {                var item = inventoryItemMap.get(k.getName());                item.releaseItem(v);            });            products.clear();        }        public void checkout(){            List<Double> prices = new ArrayList<>();            printSalesSlip();            if(products.size() <= 0) {System.out.println("There is nothing in your basket"); return;}            products.forEach((k,v) -> {                InventoryItem item = inventoryItemMap.get(k.getName().toUpperCase());                prices.add(item.salesPrice * v);                item.sellItem(v);            });            Double total = prices.stream().mapToDouble(Double::doubleValue).sum();            System.out.printf("Your total comes to: £%.2f%n",total ); //            carts.remove(this.id);        }        @Override        public String toString() {            return "%s: %s-%03d".formatted(storeName, type.toString(), id);        }    }    public Store(String storeName) {        this.storeName = storeName;        for (InventoryItem p : ProductData.getInventoryData()){            inventoryItemMap.put(p.product.getName().toUpperCase(), p);        }    }    private void updateAisles() {        inventoryItemMap.forEach((k,v) -> {            if(aisleInventory.computeIfPresent(v.product.getCategory(), (a,b) -> {                b.add(v);                return b;            }) == null){                aisleInventory.put(v.product.getCategory(), new HashSet<>(List.of(v)));            }        });    }    public void listProductsByCategory() {        updateAisles();        aisleInventory.forEach((k, v) -> {            System.out.println(k);            System.out.printf("%-21s %-19s %s%n", "Item:", "Qty:", "Price:");            v.forEach(System.out::println);            System.out.println();        });    }    public void manageStoreCarts() {        carts.forEach((k,v) -> {            if(v.date < LocalDate.now().getDayOfYear()){                v.releaseAll();            }        });        carts.values().removeIf(e -> e.date < LocalDate.now().getDayOfYear());    }    public void checkOutCarts() {        if(carts.size() > 0) {            carts.forEach((k,v) -> v.checkout());        }        carts.clear();    } }

Product public class Product {    private String sku;    private String name;    private String manufacturer;    private Category category;    public Product(String sku, String name, String manufacturer, Category category) {        this.sku = sku;        this.name = name;        this.manufacturer = manufacturer;        this.category = category;    }    public String getSku() {        return sku;    }    @Override    public boolean equals(Object o) {        if (this == o) return true;        if (o == null || getClass() != o.getClass()) return false;        Product product = (Product) o;        return getSku().equals(product.getSku());    }    @Override    public int hashCode() {        return getSku().hashCode();    }    public String getName() {        return name;    }    public Category getCategory(){        return category;    }    @Override    public String toString() {        return "%-10s %-20s %s".formatted(sku,name,manufacturer);    } }

InventoryItem public class InventoryItem {    public Product product;    private int initialStock;    private int qtyTotal;    private int qtyReserved = 0;    private int qtyReorder = 0;    private int qtyLow;    public double salesPrice;    public InventoryItem(Product product, int qtyLow, int qtyTotal, double salesPrice) {        this.initialStock = qtyTotal;        this.product = product;        this.qtyTotal = qtyTotal;        this.qtyLow = qtyLow;        this.salesPrice = salesPrice;    }    public boolean reserveItem(int amount){        if(qtyTotal - amount >= 0) {            qtyTotal -= amount;            qtyReserved += amount;            if(checkStock()){                qtyReorder = initialStock - qtyTotal;                placeInventoryOrder();            }            return true;        }        return false;    }    public void releaseItem(int amount){        qtyReserved -= amount;        qtyTotal += amount;    }    public void sellItem(int amount){        qtyReserved -= amount;    }    public void placeInventoryOrder(){        System.out.println(qtyReorder + " to be ordered");    }    private boolean checkStock(){        return (qtyTotal <= qtyLow) ? true : false;    }    @Override    public String toString() {        return "%-20s  qty:%-15s price:£%.2f".formatted(product.getName(), qtyTotal,salesPrice);    } }

Main import java.time.LocalDate; public class Main {    public static void main(String[] args) {        Store store = new Store("Gubbins Galore");        Store.Cart cart = store.new Cart(LocalDate.now().getDayOfYear(), Type.VIRTUAL);        Store.Cart cart2 = store.new Cart(LocalDate.now().getDayOfYear(), Type.PHYSICAL);        cart.addItem("bagels", 4);        cart.addItem("Apples", 3);        cart.addItem("Frozen chips", 2);        store.checkOutCarts();    } }