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Lab Assignment #2: Inheritance and polymorphism

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ENSF 607
Lab Assignment #2: Inheritance and polymorphism
The objectives of this lab are to:
1) understand the concept of class relationships, particularly inheritance.
2) get familiar with more detailsin a UML diagram, including syntax for attributes
and operations.
3) understand the concept of polymorphism.
4) implement classes in Java with inheritance, association, aggregation, and
composition relationships among them.
Exercise – 1: Drawing a Class Diagram (10 Marks)
Read This First – Generalization/specialization: During lectures, we learned that a relationship
among classes can be mainly classified as association, composition, aggregation, and inheritance,
and the focus of our previous lab was on the first three relationships. This lab focuses on
inheritance.
What is Inheritance?
Inheritance is an important type of relationship between classes which is also referred to as a
generalization/specialization relationship, or a “kind-of” relationship. An example for this type of
relationship is the relationship between class Animal and class Cat. Where, Cat is a “kind of”
animal. Thistype of relationship allows a classto be derived from an existing class. In other words,
the derived class inherits all the properties (data fields), and behaviors (methods of its base class).
UML uses the following notation (a line with a big triangular arrowhead, pointing from sub-class
(child) to the super-class (parent), to demonstrate this type of relationship.
What to Do: First, download 8 java files (Colour.java, Point.java, Text.java,
Shape.java, Rectangle.java, Circle.java, Prism.java, and
Geometry.java) from D2L. Then, read the content of these files and try to reverse-engineer
a class diagram that shows the relationship among these classes. You are expected to draw a
Post Lab (40 marks) + 5 Possible Bonus marks
Page    4 of 11
detailed class diagram that not only shows the relationships among the classes (including
multiplicities, etc.), but also the following two sets of information is required:
1. Attributes of each class.
2. Major operations in each class (constructor, getter, setter, and toString methods are not
required)
Note: abstract methods are shown in italic in UML.
What to hand in: Submit a PDF file that contains a detailed class diagram.
Page    5 of 11
Shape name: R1
Origin: X_coordinate: 3.0
Y-coordinate: 4.0
Black point
Width: 6.0
Length: 5.0
Shape name: C1
Origin: X_coordinate: 13.0
Y-coordinate: 14.0
Green point
Radius: 15.0
Shape name: R2
Origin: X_coordinate: 23.0
Y-coordinate: 24.0
Black point
Width: 26.0
Length: 25.0
Shape name: C2
Origin: X_coordinate: 33.0
Y-coordinate: 34.0
Yellow point
Radius: 35.0
Shape name: P1
Origin: X_coordinate: 43.0
Y-coordinate: 44.0
White point
Width: 46.0
Length: 45.0
height: 47.0
Shape name: P2
Origin: X_coordinate: 53.0
Y-coordinate: 54.0
Gray point
Width: 56.0
Length: 55.0
height: 57.0
Exercise – 2: Shapes (10 Marks)
What to Do: First compile the java file you downloaded for exercise 1, and run the program. Your
program should produce the following output.
Then, uncomment the last few lines of code in the Geometry.java file, under the line, which
is labeled as “SECTION 2”. If you try to compile the program now it gives you a few compilation
errors because methods: add, showAll, and calculator are missing. Your task in this
exercise is to write the definition of the missing methods as follows:
Page    6 of 11
• Method add: that adds objects of classessuch as Rectangle, Circle and Prisms
to a TreeSet list, declared in class Geometry.
• Method showAll: that displays on the screen the information about those objects that
are stored in the TreeSet list.
• Method calculator: that calculates and displays the area, perimeter, and
volume of each object on the screen.
Hint: as we discussed in lectures, to make TreeSet list working, you also need to
implement Comparable interface.
If you add the definition of the above methods your program is expected to display the
following outputs in addition to the previous outputs:
Adding Rectangle, Circle, and Prism objects to the list…
Showing information about objects added to the list:
Shape name: C1
Origin: X_coordinate: 13.0
Y-coordinate: 14.0
Green point
Radius: 15.0
Shape name: C2
Origin: X_coordinate: 33.0
Y-coordinate: 34.0
Yellow point
Radius: 35.0
Shape name: P1
Origin: X_coordinate: 43.0
Y-coordinate: 44.0
White point
Width: 46.0
Length: 45.0
height: 47.0
Shape name: P2
Origin: X_coordinate: 53.0
Y-coordinate: 54.0
Gray point
Width: 56.0
Length: 55.0
height: 57.0
Shape name: R1
Origin: X_coordinate: 3.0
Y-coordinate: 4.0
Black point
Width: 6.0
Length: 5.0
Shape name: R2
Origin: X_coordinate: 23.0
Page    7 of 11
What to hand in: Submit all the .java files in your project.
Y-coordinate: 24.0
Black point
Width: 26.0
Length: 25.0
Showing area, perimeter, and volume of objects in the list:
The area, perimeter, and volume of C1 are: 706.86, 94.25, 0.00.
The area, perimeter, and volume of C2 are: 3848.45, 219.91, 0.00.
The area, perimeter, and volume of P1 are: 12694.00, 182.00, 97290.00.
The area, perimeter, and volume of P2 are: 18814.00, 222.00, 175560.00.
The area, perimeter, and volume of R1 are: 30.00, 22.00, 0.00.
The area, perimeter, and volume of R2 are: 650.00, 102.00, 0.00.
Page    8 of 11
Exercise 3: Tic-Tac-Toe Game with the Inheritance (20 marks + 5 Bonus marks)
In this exercise, you are supposed to add a few classes to your Tic-Tac-Toe Game that developed
for assignment 1. To help you understand how to implement these classes the following class
diagram, a sample run of the program, and a brief note about the responsibilities of each class
are provided. Also, to reduce your workload the definition of class RandomGenerator and a
modified version of class Game is available to download from D2L. You can make any changes to
the code in these two files, or use a different way to solve this problem.
A Brief Description on Class HumanPlayer: HumanPlayer is a sub-class of class Player. It
is a concrete class and it has to define the abstract methods inherited from class Player. As the
following sample run shows in this new version of the game the players should have the option
of selecting the type of the players. In this example, Mike and Judy, the two players selected the
first option (i.e. human player). Which in fact is identical to what the game was doing in lab 1.
Page    9 of 11
Please enter the name of the ‘X’ player: Mike
What type of player is Mike?
1: human
2: Random Player
3: Blocking Player
4: Smart Player
Please enter a number in the range 1-4: 1
Please enter the name of the ‘O’ player: Mike’s Computer
What type of player is Mike’s Computer?
1: human
2: Random Player
3: Blocking Player
4: Smart Player
Please enter a number in the range 1-4: 2
Referee started the game…
|col 0|col 1|col 2
+ + + +
| | | |
row 0 | | | |
| | | |
+ + + +
A Brief Description on Class RandomPlayer: RandomPlayer is also a kind of Player. In
fact, this is a computer-player that uses a random generator and picks a vacant spot on the board,
randomly. The following example shows part of the game between a human (Mike) and his
computer. As you can see in the sample run, Mike’s Computer plays randomly and places an Omark in a randomly selected empty place immediately after Mike moves, and without any
interaction for entering the row or the column number.
Please enter the name of the ‘X’ player: Mike
What type of player is Mike?
1: human
2: Random Player
3: Blocking Player
4: Smart Player
Please enter a number in the range 1-4: 1
Please enter the name of the ‘O’ player: Judy
What type of player is Judy?
1: human
2: Random Player
3: Blocking Player
4: Smart Player
Please enter a number in the range 1-4: 1


<<< game is continued similar to lab 2>>>
Page    10 of 11
Hint: You need to override the definition of method makeMove. Feel free to come up with your
own algorithm, but here is a suggestion:
Call the method discrete from class RandomGenerator twice to return random
values between 0 and 2 (if you have 3*3 board) for i and j, if the board[i][j] is
available (i.e. empty), then mark it. If the cell is not available, repeat the procedure, until
you find an empty spot.
Once your method makeMove is completely defined, test it by compiling and running your
program a few times. Do not move to the next step until definition of the methods in this class is
complete and error free.
|
row 1 |
|
+
|
row 2 |
|
+
|
|
|
+
|
|
|
+
|
|
|
+
|
|
|
+
|
|
|
+
|
|
|
+
Mike, what row should your next X be placed in? 1
Mike, what column should your next X be placed in? 1
|col 0|col 1|col 2
+ + + +
| | | |
row 0 | | | |
| | | |
+ + + +
| | | |
row 1 | | X | |
| | | |
+ + + +
| | | |
row 2 | | | |
| | | |
+ + + +
|col 0|col 1|col 2
+ + + +
| | | |
row 0 | | | |
| | | |
+ + + +
| | | |
row 1 | | X | |
| | | |
+ + + +
| | | |
row 2 | | | O |
| | | |
+ + + +
Mike, what row should your next X be placed in? 1
Mike, what column should your next X be placed in? 0

<<< game is continued >>>
Page    11 of 11
A Brief Description on Class BlockingPlayer: A BlockingPlayer is kind of RandomPlayer
that first looks at the board for a move that would block its opponent from winning on the next
move. If it can’t find any such move, it picks a vacant spot at random. Therefore, before making
any move, this class needs to call a method called testForBlocking. This method should
return true if there is a situation that needs to be blocked. In other words, the process is to
traverse through the board, and call testForBlocking method for each spot (ith row and jth
column). If the function returns true for any of the i
th row and j
th column, put a mark in that spot,
otherwise select an empty random spot (same as RandomPlayer).
Optional(Bonus) – Implementation of class SmartPlayer is optional.
A Brief Description on Class SmartPlayer: A SmartPlayer is a kind of BlockingPlayer,
but slightly smarter and takes the following steps to move:
1. First looks at board, if it can find a move to win immediately, it makes that move.
2. Otherwise, it looks for a way to block its opponent’s from winning on the next move.
3. Otherwise, it picks a vacant square at random.
What to hand in: Submit all your source file (.java files). You do not need to submit any
javadoc HTML files for this exercise.

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