These are the specifications for labs for each of the design patterns we are covering.

Each part builds upon the previous part to demonstrate how design patterns can work together

To ensure that your implementation meets the desired requirements, remember to write tests for each behavior you are implementing. Following the principles of Test Driven Development will help to ensure a functioning end product at the end of these labs.

Implement the Factory Method pattern in the hierarchy for CupDispenser to mirror that of the DrinkDispenser. You should implement subclasses CoffeeCupDispenser, BeerGlassDispenser, and SodaCupDispenser. You may also want to implement the classes CoffeeCup, BeerGlass and SodaCup.

Follow the Abstract Factory pattern to complete the hierarchy for the DispensingSystem. Include at least two concrete dispensing systems of your choice and fill in any missing components needed. (Eg: if you want to make a BeerDispensingSystem you will need to create the Beer and BeerDispenser classes, which we did not make yet)

The various dispensers we created in the previous lab don't have any internal state, so it may not make sense to create new ones every time we request a dispenser. Turn the various subclasses of DrinkDispenser and CupDispenser into singletons so that only one instance of each is created when requesting them from the various Dispensing Systems.

• Here is a brief article discussing Java singletons in greater depth

When you go to a restaurant (or diner or coffee shop) you don't usually expect to have to construct your drink yourself -- you just order it, and shortly afterward the server returns with your drink. Implement the Facade pattern in the form of a class called DrinkServer that that handles the process of serving you a drink, and all you have to know is how to orderCoffee(), orderSoda() or orderBeer()

Let's keep track of how much of each beverage each server sells. We can do this using the observer pattern and the built in Observable class and Observer interface in Java. Refactor your DrinkServer to extend the Observable class and notify its observers each time a drink is served. The notification should include a description of what drink was served.