To get the programme to work, you will need to define all the classes and methods described in this document. However, you are advised to do this in stages. Attempt the code in Section 3 before going on to Section 4. Implement one class at a time, and compile often, correcting compiler errors as you go. You should first compile individual classes to ensure they are self-consistent before trying to compile higher level classes (those that use other classes you have written).

For some methods, you have been provided with signatures either in the code or in this document. Where this is the case, you should write methods that match these signatures. This means:

  • Do not change the return type.
  • Do not change the visibility, e.g. public.
  • Do not change the number or type of input arguments.
  • Do not change whether a method is static or not.

In other cases, you will need to make a descision on what the best signature is for your method, e.g. the equals methods, or the constructor for UnitaryOrder. You may also write your own additional methods in any way you see fit. In some cases, it may be easier to solve the problem if you define helper methods, and you will be given credit if these are used appropriately.

You may also add attributes to any of the classes. In particular, you will have to add attributes to the PreboxedProduct, PackagedProduct and UnitaryOrder classes. You can add any additional attributes you deem appropriate.

There is more than one way to solve this problem, and where you meet the specification you will be given credit up to a maximum of 70%: 40% for the product-list classes, and 30% for the basket classes. Additional marks will be given for coding style and comments, up to a maximum of 30%. This includes, but is not limited to:

  • appropriate properties of attributes, e.g. public, private, protected, static and final
  • appropriate use of control flow, e.g. loops, if/switch statements and recursion
  • appropriate variables with good names
  • code reuse and minimising duplication of code
  • appropriate helper methods & additional classes
  • appropriate use and handling of exceptions
  • meaningful and appropriate comments
  • consistent formatting of code.
  • good package structure

When you are ready

When you are ready, upload a zip file of your code. This should contain all your code in a single zip file, and should preserve the folder structure that matches your package structure. Upload this to the submission webpage of moodle.

An Online Food Store's Product List

For this assessment, you must write code to support an online dry-food delivery service. The store has three different kinds of products, including loose-products (those sold by weight), preboxed- products (those already in boxes for delivery), and packaged-products (those in packages, that must be packed into boxes for delivery). When your code is fully implemented, the main class FoodStoreProg will run a simple interactive interface for a user: to see products available to them at your online-store; to select one or more products, by weight or quantity, and add them to their basket; and to see a running subtotal, postage price, and total price of their basket. Some of the code in FoodStoreProg has been commented out, to help you to solve part of the problem, before moving on to the other part. Initially, FoodStoreProg will only print a product-list to screen.

You should begin by completing the implementation of ProductList, Product and the subclasses of Product, the requirements are described in more detail in Section 3. After which, you should at- tempt to implement Basket, BasketItem and the implementing classes of BasketItem, the require- ments are described in more detail in Section 4. You have also been given a class PriceFormatter which gives you a simple way of converting int prices into Strings. (You do not need to edit this class.) Until you complete Section 3, you do not need to edit FoodStoreProg. When you get to Section 4, you should uncomment the remaining code in FoodStoreProg.

Postage

One of the key challenges in this coursework is calculating appropriate postage cost for a customers order. This section outline the rules that you should follow to achieve this. Throughout the coursework description, the text will refer you back to this section when it is relevant.

The online store follows the following rules when posting out products to customers:

  • The online store uses Royal Mails parcel service to fulfil its deliveries.
  • Deliveries are sent out by Royal Mail, either as small parcels or as medium parcel (we call these non-small parcels).
  • The store only delivers to the UK, and the postage costs for parcels of various weights are shown in Table 1.
  • Different products are always sent out in separate parcels.
  • Loose-products are always sent in small parcels, and as many full weight (2kg) parcels as possible are used. (You can assume 2kg of any loose product will fit in a small parcel.)
  • Preboxed-products can either be in small or non-small parcels. If in a small parcel, then the weight will always be under 2kg. If in a non-small parcel, then the weight will be under 20kg.
parcel max weight postage cost
small 2kg £3.95
non-small 2kg £6.05
non-small 5kg £14.85
non-small 10kg £21.35
non-small 20kg £29.65
Table 1: Royal Mail's UK parcel rates
  • Packaged-products are packed into either small or non-small parcels and:
    • For each packaged product, there is a known maximum quantity that will fit into a small parcel, and a (larger) maximum quantity that will fit into a non-small parcel.
    • If a packaged product order can be fit into a single small parcel, then it will be.
    • When a customer orders a larger quantity of a packaged product, as many full, non-small parcels will be sent as possible.
    • When it is no longer possible to fill a non-small parcel: the remainder will be sent in a single small parcel if possible; otherwise, a partially full, non-small parcel will be used.
  • For instance, one packaged-product is the Dried mango pack. Each pack weighs 0.13kg; a maximum of 7 packs can fit into a small-parcel; and a maximum of 100 packs can fit into a non-small parcel. If a customer orders:
    • 7 or fewer packs will be packed into a single small parcel
    • 8 100 packs will be packed into a single non-small parcel
    • 101 107 packs one full non-small parcel and a small parcel will be used.
    • 108 200 packs two non-small parcels will be used (at least one will be full).
    • ...

Creating the Product-List

A product-list can contain different kinds of products, including loose-products, preboxed-products, and packaged-products. To capture this, you should complete the LooseProduct and ProductList classes, as well as writing two additional classes PreboxedProduct and PackagedProduct.

Look at the UML class diagram in Figure 1. This shows the classes relevant to this part of the coursework. The green class has already been implemented for you, the yellow classes have been partly implemented but require some additional implementation from you, and the orange classes should be fully implemented by you. In particular, you will need to implement PreboxedProduct and PackagedProduct classes from scratch.

The class LooseProduct has been partly implemented for you, and extends the Product abstract class. This is a good place to start. You will then need to write PreboxedProduct and PackagedProduct from scratch. You can use the existing content of LooseProduct to help with this. However, you need to decide whether PreboxedProduct and PackagedProduct are direct subclasses or whether you should structure the class hierarchy differently. When these three classes are implemented, you should implement the getDefaultProductList static method in ProductList. This will populate a new ProductList with examples of the three kinds of products.

Figure 1: A UML class diagram of the ProductList class and its related classes and interfaces. see image.

Once you have implemented the classes in the section, you should be able to compile and run the code, and it will create an example product-list then print it to the screen. The roles of the different classes in Figure 1, and the changes you have to make, are described in more detail below.

The Product class

Product is an abstract class that represents items that can appear on the product-list. You do not have to make any changes to this class. The attributes have the following meanings:

  • NAME represents the product name (or a very short description)
  • MAXLENGTHNAME maximum length of the product name
  • SMALLPARCELPOSTAGE2KG postage cost of small parcels under 2kg in weight
  • PARCELPOSTAGE2KG postage cost of standard (non-small) parcels under 2kg in weight
  • PARCELPOSTAGE5KG postage cost of standard (non-small) parcels under 5kg in weight
  • PARCELPOSTAGE10KG postage cost of standard (non-small) parcels under 10kg in weight
  • PARCELPOSTAGE20KG postage cost of standard (non-small) parcels under 20kg in weight

Key methods in this class are:

  • A constructor that takes 1 argument the name of the product.
  • toProductListEntry an abstract method. Concrete subclasses of Product should imple- ment toProductListEntry so that it returns a line of text showing the product name and various other details for the item (this is described in more detail for each extending class).

The constructor is already implemented. Additionally, a standard getter method, and the method getPaddedName have also been implemented for you. getPaddedName produces a fixed length string (24 characters) containing the Products name, and is to help you write the toProductListEntry method. While there is no need to edit this class, you may find that it is a good place to define helper methods for other classes. This is left to your judgement.

The LooseProduct class

LooseProduct is a direct concrete subclass of Product that represents loose (unpackaged) products available at your store. Customers order these by weight, and for simplicity, we allow any positive weight to be ordered. As well as inheriting a name, a LooseProduct records the price per kilo (in the attribute PRICEPERKILO). Some details of the key methods are as follows:

  • A constructor that takes arguments: name and pricePerKilo (with the expected meanings).
  • getPricePerKilo a simple getter method for the PRICEPERKILO attribute.
  • toProductListEntry This overrides the corresponding abstract method in Product. It takes an int input argument id, and returns a line of text showing (in the following order): the product id, the name, the string "(per kg)", and the price per kilo. For example:
LooseProduct loose1 = new LooseProduct("Star Anise", 1990);
LooseProduct loose2 = new LooseProduct("Methi Seeds", 2490);
System.out.println(loose1.toProductListEntry(6));
System.out.println(loose2.toProductListEntry(17));

should produce output similar to:

006: Star Anise (per kg) 19.90
017: Methi Seeds (per kg) 24.90
  • getPrice This takes a double weight as input, and returns the price, in pence, of the given weight of the loose-product.
  • getPostage This takes a double weight as input, and returns the postage price, in pence, of the given weight of the loose-product. Refer to Section 2.1 for a description of how this is to be calculated.
  • equals You should implement a standard equals method to allow any LooseProduct to be compared to any other object. This should return true if and only if the other object is a LooseProduct and has identical attribute values. You may choose to implement an additional method to adhere to good coding style.

Look at the code or Figure 1 for more details.

The PreboxedProduct class

You will need to create this class and write all the specified methods. You may add any fields or additional methods you require. PreboxedProduct is a concrete subclass of Product that represents preboxed products (those already in boxes suitable as parcels). Customers order these in terms of units (which must be whole numbers). As well as inheriting a name, a PreboxedProduct must record: the unit-price, the unit-weight, and whether it is sent as a small-parcel or not. The details of the required methods are as follows:

  • A constructor that takes arguments: name, unitPrice, unitWeight, and inSmallParcel with the expected meanings. (See the UML diagram for the type information.)
  • Simple getter methods for any attributes.
  • toProductListEntry This overrides the corresponding abstract method in Product. It takes an int input argument id, and returns a line of text showing (in the following order): the product id, the name, the weight in brackets and the unit price. For example, the code:
PreboxedProduct prebox1 = new PreboxedProduct("Red Camargue Rice", 1400, 2.0, true);
PreboxedProduct prebox2 = new PreboxedProduct("Kettle Barbeque", 3500, 5.0, false);
System.out.println(prebox1.toProductListEntry(1));
System.out.println(prebox2.toProductListEntry(22));

should produce output similar to:

001: Red Camargue Rice (2.00kg) 14.00
022: Kettle Barbeque (5.00kg) 35.00
  • getPrice This takes an int units as input, and returns the price, in pence, of the given number of units of the preboxed-product. Note that this method has a different signa- ture to LooseProduct.getPrice (as it takes an int not a double).
  • getPostage This takes a int units as input, and returns the postage price, in pence, of the given number of units of the preboxed-product. Refer to Section 2.1 for a description of how this is to be calculated. Note that this method has a different signature to LooseProduct.getPostage (as it takes an int not a double).
  • equals You should implement a standard equals method to allow any PreboxedProduct to be compared to any other object. This should return true if and only if the other object is a PreboxedProduct and has identical attribute values. You may choose to implement an additional method to adhere to good coding style.

Look at the code or Figure 1 for more details.

The PackagedProduct class

You will need to create this class and write all the specified methods. You may add any fields or additional methods you require. PackagedProduct is a concrete subclass of Product that represents packaged products (those needing to be packaged into parcels for delivery). Customers order these in terms of units (which must be whole numbers). As well as inheriting a name, a PackagedProduct must record: the unit-price, the unit-weight, and whether it is sent as a small-parcel or not. The details of the required methods are as follows:

  • A constructor that takes arguments: name, unitPrice, unitWeight, maxPerSmlParcel and maxPerParcel (for non-small parcels) with the expected meanings. (See the UML diagram for the type information.)
  • Simple getter methods for any attributes.
  • toProductListEntry This has the same requirements PreboxedProduct.toProductListEntry, but applied to a PackagedProduct. For example:
PackagedProduct packaged1 = new PackagedProduct("Dried Mangosteen Pack", 269, 0.13, 7,
100);
PackagedProduct packaged2 = new PackagedProduct("Dried Durian Pack", 550, 0.26, 3, 50);
System.out.println(packaged1.toProductListEntry(9));
System.out.println(packaged2.toProductListEntry(10));

should produce output similar to:

009: Dried Mangosteen Pack (0.13kg) 2.69
010: Dried Durian Pack (0.26kg) 5.50
  • getPrice and getPostage These have the same requirements as PreboxedProduct.getPrice and PreboxedProduct.getPostage respectively, but applied to a PackagedProduct.
  • equals You should implement a standard equals method to allow any PackagedProduct to be compared to any other object. This should return true if and only if the other object is a PackagedProduct and has identical attribute values. You may choose to implement an additional method to adhere to good coding style.

Look at the code or Figure 1 for more details.

The ProductList class

ProductList is a simple class for holding a collection of Products, displaying them to screen, and selecting them based on their ids. You will need to edit the createDefaultProductList to create a number of loose, preboxed and packaged product descriptions for your online store. You only need to edit one method in this class. You may add any fields or additional methods you require.

createExampleProductList is a static method that creates a new ProductList object, and pop- ulates it with PreboxedProduct, PackagedProduct and LooseProduct objects. You should choose a name for your online store, and add at least 4 packaged products, 3 preboxed products and 2 loose products to the list (remember to include a variety). There are some examples of preboxed products, packaged products and loose products to guide you; please replace these with your own descriptions.

A Customers Basket

Do not attempt this part until you have attempted to implement the classes required by Section 3. You should now implement the classes that will allow customers to order items from the product-list, and to keep track of these orders. Begin by looking at Figure 2. The interface in green has been provided for you, and does not need any changes. The classes in yellow will require some implementation from you. The class in orange must be written from scratch. To test your changes in this section you should uncomment the remaining code in FoodStoreProg.

Figure 2: A UML class diagram of the Basket class and its related classes and interfaces. see image.

The BasketItem interface

This interface has been written for you and you should not make any changes to it.

Any class that implements the BasketItem interface represents an entry in a customers basket and corresponds to an amount of a given Product. As described below, this can be WeightOrder, which represents an order for some weight of a LooseProduct. Alternatively, a basket-item can be for a UnitaryOrder which represents an order for a number of units of either a PreboxedProduct or a PackagedProduct. WeightOrder has been partly written for you and is a good place to start. You will need to implement UnitaryOrder from scratch.

Key methods that implementing classes will need to define are:

  • orderPrice: returns the price in pence of the order.
  • postagePrice: returns the postage price in pence of the order.
  • matchesProduct: takes any Product as input, and returns true if this matches the basket- items Product, and false otherwise.
  • amendOrder: takes a String quantityStr corresponding to a new amount for the order. quantityStr must represent real value for a WeightOrder, or an integer value for a UnitaryOrder.
  • toString: returns a String with the order-price followed by a description of the order. The order-entry price should be that calculated by orderPrice method. The postage-price is not displayed here.

Hint: You should try to make use of the methods you have already defined in Section 3 when writing the implementing classes. You may also want to make use of the library methods Integer.parseInt or Double.parseDouble when implementing amendOrder.

The WeightOrder class

An object of type WeightOrder represents a customers desire to purchase some weight of a par- ticular LooseProduct. This class should implement the BasketItem interface. The class has been partly implemented for you. It includes two attributes: PRODUCT the LooseProduct being ordered; and weight the ordered weight in kilogrammes.

The UnitaryOrder class

You will need to create this class and write all the specified methods. You may add any fields or additional methods you require.

An object of type UnitaryOrder represents a customers desire to purchase one or more units of a particular PreboxedProduct or PackagedProduct. This class should implement the BasketItem interface, and should store the product and number of units ordered.

The Basket class

Basket is a simple class for holding a customers basket in terms of a collection of BasketItems. It should display this basket to screen, calculate the total price and do so taking account of any discounts. Key methods that you will need to implement in this class are:

  • inBasket: takes a Product as input. Method returns true if a basket-item matches this product, and false otherwise.
  • addNewOrder: adds a BasketItem to the Basket. The input argument product represents the Product desired. If product is a LooseProduct then quantityStr represents the weight desired. If product is a PreboxedProduct or PackagedProduct then quantityStr represents the number of units desired.
  • Hint: To check whether the type of a Product you will find the instanceof keyword helpful. You may also need to downcast.
  • amendOrder: Changes the order quantity for an existing basket-item. The input arguments have the same meaning as in addNewOrder.
  • calculateSubtotal: takes no arguments and returns the total-price before postage of the current order (in pence).
  • Hint: You may want to make use of each basket items orderPrice method.
  • calculatePostage: takes no arguments and returns the total-postage price of the current order (in pence), taking account of any discounts applied.
  • Hint: You may want to make use of each basket items postagePrice method.

A constructor, calculateTotal and the toString method have been implemented for you.

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