Object Oriented Design and Programming Assignment 2

CSIT121
Object Oriented Design and Programming
Assignment 2
File name: YourName _ClassListNo_A2.java
Objectives:
Practice java programming with inheritance and polymorphism.
Task (6 marks)
Implement the Shape hierarchy shown in Fig. 1 (Class name in italic
indicates an abstract class).

- Basically each TwoDimensionalShape has an area method
computes and returns the area of the two-dimensional shape. Try to
have a private computeArea method (do the computation), and area
method returns the computed area; though this method was not shown
in the UML diagram.
Rectangle
Resizable
Trapezoid 
2
- Each ThreeDimensionalShape other than the area method we
also have a volume method; computes and returns, respectively, the
surface area and the volume of the three-dimensional shape. Likewise
have two private computeArea and computeVolume methods in
the design though these two methods were not shown in the UML
diagram.
- Try to surf the internet to look for some formulas, for example, to
compute the areas, the surface areas and the volumes … I did that too

- The following UML diagram show briefly the overall design:
Let us break the design into 2 parts: 2D and 3D.
A more detailed UML diagram is shown as follow: (Note that the #’s before
the instance variables and the methods’ names mean “protected”)
3
Wow … so difficult to see; no worry, I will break it down bit by bit and
explain what you have to do …
Let us explore the above UML diagram at the highest hierarchy; you can see
that Shape is an interface class. Two abstract classes TwoD and ThreeD
implement the Shape interface; ThreeD also implements Resizable
interface and we also have an enumeration data type to describe some of the
colors: 
4
Four possible shapes for TwoD: one value, for example the radius, is a circle
shape; two values, for example the length and the width, is a rectangle; three
values for example the three sides of a triangle (provided it can be formed),
five values for trapezoid (one additional value was the height, as we need
that to compute the area). In this class, you can see that we have four
constructors to describe the four shapes, a copy constructor, some accessor
and mutator methods and a toString method. Each 2D shape also has a
color. You can see we define an enumeration type to specify the color of the
shapes.
The following UML diagram shows the four concrete subclasses of TwoD: 
5

Some methods just override the super class methods (same
implementations)
Information defined in each of the subclasses should be obvious in
definitions, don’t forget the private method that I have just mentioned 
Now, let us look at the ThreeD class:

Three possible shapes for ThreeD: Just one value can determine the shapes
of a sphere, a cube and or a tetrahedron. In this class, we only also have
constructors, copy constructor, accessor methods, mutator methods and a
toString method. For a 3D object, we can compute and return the volume
too. Therefore we have one abstract method in this abstract class ThreeD.
ThreeD class also implements Resizable interface class. In this
Resizable interface, other than the method resize, to reduce the size by
certain percentage; therefore in this class, we also have constant specifying
the percentage of the size to be reduced. 
6
 Let us now look at the UML diagram for the three subclasses of ThreeD
class:
Look for the surface area and volume formulas somewhere in internet to
compute and to return their values, also don’t forget the two private methods
I have just mentioned 
Note that all 3D objects need to resize by a certain percentage.
Let us now explore the main class, i.e. main method is defined in this class 
7
All shapes (2D or 3D) should be randomly generated and store them in an
ArrayList of Shape’s.
You can see a few private class methods are defined in this class
YourName_A2 (remember to replace by your own name):
- a method generates and returns a positive integer, not too large
- a method generates and returns a positive real number, not too large
- a method generates and returns a color.
- a method generates and returns a TwoD shape
- a method generates and returns a ThreeD shape
- a method to display the objects stored in the ArrayList. Note that in
the display method, you display the details of each shape object, i.e.
the toString method for each of the classes only display a “brief”
object info, display of area / volume / resizable should be done in this
method.
Convenient to your design, minor updates to methods or additional methods
are allowed.
In the main method, you repeatedly generate an integer k (0 or 1 or 2). If k
is 1 you construct a 2D object; if k is 2, you construct a 3D object and k is 0,
you end the task. The following shows one of the possible displays: 
8
Four objects were generated and stored in the array list and you displayed
the list. You can see Shape 2 and Shape 3 were 3D objects, their sizes, area,
volume were reduced by 10%.
Note that the list may be empty …
IMPORTANT
Put all your classes in a file called
YourName_ClassListNo_A2.java and make sure that this
file can be compiled and can be executed. Upload ONLY this file
to Moodle. ALL ZIP FILE SUBMISSION WILL BE
REJECTED.
No re-submission will be allowed after grading. 
9
In the above file, remember to put down your name and also the
following declaration (some similar contents):
// Tell me if it is your own work, and whether you
// have passed your program to your friends etc etc etc
// and willing to accept whatever penalty given to you.
- Wrong file name -0.5 mark
- No declaration, no name etc -0.5 mark
- Failing to demo -1 mark
- Programs indentations and alignment of
statements -0.5 mark
- Late penalty: -0.1 mark per hour.