Refining Your OO Design

P2: Refining Your OO Design

(41 marks)

Focus: polymorphism, abstract classes, interfaces

In this part, you will refine the design you created in P1 of the project. You will add more code and change some of the existing code. Start by downloading the starter_code that comes with this assignment then do as required below.

(A) the Animal class:

[6 marks]

o   [+1] Change Animal to an abstract class.

     [+2] Explain in a comment in your program why it makes sense for this class to be abstract.

o   [+1] Change sound() to an abstract method.

     [+2] Explain in a comment why it makes sense for this method to be abstract. Why don’t we just remove it from Animal and keep it in the subclasses?

(B) the Farm class:

[34 marks]

o   [+1] change your code so that the animals array will have enough space for a 100 animals.

(No need to add a 100 animals in the Farm’s constructor – see the next two points).

o   [+4] Add a method boolean add(Animal anim) that adds an animal to the next empty spot in the animals array. For example, when you first create animals, it will have a 100 empty spots (i.e. all null). The code below adds a new chicken at index 0 and a cow at index 1.

The remaining spots will remain empty (i.e. equal to null).

myFarm.add(new Chicken());

myFarm.add(new Cow());

The add method should return true when the given animal is added successfully, and false when the farm is full (i.e. no empty spots in animals array).

o   [+1] modify the Farm’s constructor to use the above add method in order to add a chicken, a cow, and two llamas. The animals array should now have exactly 4 animals and 96 empty spots.

o   [+3] modify the getAnimals method so that it returns an array with existing animals only (i.e. don't return the full animals array if it has empty spots). For example, if you have only 4 animals in your farm, getAnimals will return a new array of the size 4 with these 4 animals.

o   [+4] Add a method void animSort() that sorts the animals in the animals array based on their energy. You must use the Arrays.sort method in your implementation. For example, suppose that

animals = [Cow1, Chicken1, Llama1, null, null, …, null]

and assume that the order based on the energy is Llama1 < Chicken1 < Cow1. Then, animSort would change animals to:

animals = [Llama1, Chicken1, Cow1, null, null, …, null]

Note that Arrays.sort cannot sort null values.

     [+4] Implement any changes outside the Farm class in order for animSort() to work properly. 

o   [+2] Add a method boolean addClone(Animal anim) that clones the given animal, anim, and adds it to the animals array. For example, if animals has 4 animals and we call myFarm.addClone(animals[2]), a clone of animals[2] would be created and added to animals at the next available spot. The method addClone returns true if the animal is added successfully to animals and false if the farm is full.

     [+4] Implement any changes outside the Farm class in order for addClone to work properly.

o   [+3] Add a method printAnimals that will print the list of animals currently living in the farm. For example, if myFarm has only two animals, then myFarm.printAnimals() may print this output:

Chicken1: alive at (0.0,0.0) Energy=28.9

Cow1 : alive at (0.0,0.0) Energy=87.5

o   [+4] Add a method int getNumChicken()that returns the number of chicken in the farm.

     [+2] Add two more methods, getNumCows()and getNumLlamas() that return the number of cows and llamas on the farm. (hint: use instanceof).

o   [+2] Add a method void printSummary() that prints the total number of animals, the number of each animal type, and the amount of available food (see sample output in part C below).

(C) update the FarmTest class with the code given below.

[1 mark]

public class FarmTest {

public static void main(String[] args) throws CloneNotSupportedException {

Farm myFarm = new Farm();

for(Animal a: myFarm.getAnimals())

a.setEnergy(Math.random()*100);

System.out.println("\nInitial list of animals:\n-------------------------");

myFarm.printAnimals();

System.out.println("\nAdding a clone of the second animal\n-----------------------------------");

myFarm.addClone(myFarm.getAnimals()[1]);

myFarm.printAnimals();

System.out.println("\nAfter SORTING:\n--------------");

myFarm.animSort();

myFarm.printAnimals();

System.out.println("\nFarm summary:\n--------------");

myFarm.printSummary();

}

}

Above code should print an output similar to the one below. Note that this output may be slightly different based on several factors such as your animals’ energy and the available food in the farm.

Chicken1 says: I'm hungry

Initial list of animals:

-------------------------

Chicken1: alive at (0.0,0.0) Energy=44.5

Cow1 : alive at (0.0,0.0) Energy=98.2

Llama1 : alive at (0.0,0.0) Energy=72.4

Llama2 : alive at (0.0,0.0) Energy=94.3

Adding a clone of the second animal

-----------------------------------

Chicken1: alive at (0.0,0.0) Energy=44.5

Cow1 : alive at (0.0,0.0) Energy=98.2

Llama1 : alive at (0.0,0.0) Energy=72.4

Llama2 : alive at (0.0,0.0) Energy=94.3

Cow1 : alive at (0.0,0.0) Energy=98.2

After SORTING:

--------------

Chicken1: alive at (0.0,0.0) Energy=44.5

Llama1 : alive at (0.0,0.0) Energy=72.4

Llama2 : alive at (0.0,0.0) Energy=94.3

Cow1 : alive at (0.0,0.0) Energy=98.2

Cow1 : alive at (0.0,0.0) Energy=98.2

Farm summary:

--------------

The farm has:

- 5 animals (1 Chicken, 2 Cows, and 2 Llamas)

- 1000 units of available food

Submission Instructions

For this part of the project, you need to do the following:

1-   Create a Java project of with any name of your choice.

2-   Create package with the name P2 and write your code within this package.

3-   Zip the ‘src’ folder in the package P2 and name the zipped file as: YourStudentID_P2. e.g., “1234567_P2”.

4-   Submit the zipped file to Canvas.

Note that you can resubmit an assignment one more time, but the new submission overwrites the old submission and receives a new timestamp.