Description
Overview: You will write a program this week that is composed of two classes: (1) one named
Icosahedron that defines Icosahedron objects, and (2) the other, IcosahedronApp, which has a main
method that reads in data, creates an Icosahedron object, and then prints the object.
An Icosahedron has 20 equilateral triangle faces, 12 vertices, and 30 edges as depicted below. The
formulas are provided to assist you in computing return values for the respective methods in the
Icosahedron class described in this project.
Surface Area (A)
Volume (V)
Edge length (a)
Surface/Volume ratio (A/V)
• Icosahedron.java
Requirements: Create an Icosahedron class that stores the label, color, and edge (i.e., length of
an edge, which must be greater than zero). The Icosahedron class also includes methods to set
and get each of these fields, as well as methods to calculate the surface area, volume, and surface
to volume ratio of an Icosahedron object, and a method to provide a String value of an
Icosahedron object (i.e., a class instance).
Project: Icosahedron App Page 2 of 4
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Design: The Icosahedron class has fields, a constructor, and methods as outlined below.
(1) Fields (instance variables): label of type String, color of type String, and edge of type double.
Initialize the Strings to “” and the double to 0 in their respective declarations. These instance
variables should be private so that they are not directly accessible from outside of the
Icosahedron class, and these should be the only instance variables in the class.
(2) Constructor: Your Icosahedron class must contain a public constructor that accepts three
parameters (see types of above) representing the label, color, and edge. Instead of assigning
the parameters directly to the fields, the respective set method for each field (described
below) should be called. For example, instead of the statement label = labelIn; use
the statement setLabel(labelIn); Below are examples of how the constructor could
be used to create Icosahedron objects. Note that although String and numeric literals are used
for the actual parameters (or arguments) in these examples, variables of the required type
could have been used instead of the literals.
Icosahedron example1 = new Icosahedron(“Small”, “blue”, 0.01);
Icosahedron example2 = new Icosahedron(” Medium “, “orange”, 12.3);
Icosahedron example3 = new Icosahedron(“Large”, ” white “, 123.4);
(3) Methods: Usually a class provides methods to access and modify each of its instance
variables (known as get and set methods) along with any other required methods. The
methods for Icosahedron, which should each be public, are described below. See formulas in
Code and Test below.
o getLabel: Accepts no parameters and returns a String representing the label field.
o setLabel: Takes a String parameter and returns a boolean. If the string parameter is
not null, then the “trimmed” String is set to the label field and the method returns true.
Otherwise, the method returns false and the label is not set.
o getColor: Accepts no parameters and returns a String representing the color field.
o setColor: Takes a String parameter and returns a boolean. If the string parameter is
not null, then the “trimmed” String is set to the color field and the method returns true.
Otherwise, the method returns false and the label is not set.
o getEdge: Accepts no parameters and returns a double representing the edge field.
o setEdge: Accepts a double parameter and returns a boolean as follows. If the edge is
greater than zero, sets the edge field to the double passed in and returns true. Otherwise,
the method returns false and the edge is not set.
o surfaceArea: Accepts no parameters and returns the double value for the total
surface area calculated using the value for edge.
o volume: Accepts no parameters and returns the double value for the volume calculated
using the value for edge.
o surfaceToVolumeRatio: Accepts no parameters and returns the double value
calculated by dividing the total surface area by the volume.
Project: Icosahedron App Page 3 of 4
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o toString: Returns a String containing the information about the Icosahedron object
formatted as shown below, including decimal formatting (“#,##0.0#####”) for the
double values. Newline and tab escape sequences should be used to achieve the proper
layout. In addition to the field values (or corresponding “get” methods), the following
methods should be used to compute appropriate values in the toString method:
surfaceArea(), volume(), and surfaceToVolumeRatio(). Each line should have
no trailing spaces (e.g., there should be no spaces before a newline (\n) character). The
toString value for example1, example2, and example3 respectively are shown
below (the blank lines are not part of the toString values).
Icosahedron “Small” is “blue” with 30 edges of length 0.01 units.
surface area = 0.000866 square units
volume = 0.000002 cubic units
surface/volume ratio = 396.950723
Icosahedron “Medium” is “orange” with 30 edges of length 12.3 units.
surface area = 1,310.209833 square units
volume = 4,059.844212 cubic units
surface/volume ratio = 0.322724
Icosahedron “Large” is “white” with 30 edges of length 123.4 units.
surface area = 131,874.537977 square units
volume = 4,099,581.395236 cubic units
surface/volume ratio = 0.032168
Code and Test: As you implement your Icosahedron class, you should compile it and then test it
using interactions. For example, as soon you have implemented and successfully compiled the
constructor, you should create instances of Icosahedron in interactions (e.g., copy/paste the
examples above). Remember that when you have an instance on the workbench, you can unfold
it to see its values. You can also open a viewer canvas window and drag the instance from the
Workbench tab to the canvas window. After you have implemented and compiled one or more
methods, create an Icosahedron object in interactions and invoke each of your methods on the
object to make sure the methods are working as intended. You may find it useful to create a
separate class with a main method that creates an instance of Icosahedron then prints it out. This
would be similar to the IcosahedronApp class you will create below, except that in the
IcosahedronApp class you will read in the values and then create and print the object.
• IcosahedronApp.java
Requirements: Create an IcosahedronApp class with a main method that reads in values for
label, color, and edge length. After the values have been read in, main creates an Icosahedron
object and then prints a new line and the object.
Design: The main method should prompt the user to enter the label, color, and edge. After a
value is read in for edge, if the value is less than or equal to zero, an appropriate message (see
examples below) should be printed followed by a return from main. Assuming that edge is
positive, an Icosahedron object should be created and printed. Below is an example where the
user has entered a non-positive value for edge followed by an example using the values from the
first example above for label, color, and edge. Your program input/output should be exactly as
follows.
Project: Icosahedron App Page 4 of 4
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Line # Program input/output
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2
3
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5
Enter label, color, and edge length for an icosahedron.
label: icosahedron with a bad edge value
color: yellow
edge: 0
Error: edge must be greater than 0.
Line # Program input/output
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2
3
4
5
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9
Enter label, color, and edge length for an icosahedron.
label: Small
color: blue
edge: 0.01
Icosahedron “Small” is “blue” with 30 edges of length 0.01 units.
surface area = 0.000866 square units
volume = 0.000002 cubic units
surface/volume ratio = 396.950723
Code: Your program should use the nextLine method of the Scanner class to read user input.
Note that this method returns the input as a String. Whenever necessary, you can use the
Double.parseDouble method to convert the input String to a double. For example:
Double.parseDouble(s1) will return the double value represented by String s1. For the
printed lines requesting input for label, color, and edge, use a tab “\t” rather than three spaces.
After you have created the object, it can be printed simply by using its variable name; i.e., when
the object variable name is evaluated in the println statement, its toString() method is
automatically called. Thus, printing the object reference variable myObj is equivalent to printing
the return value of the myObj.toString() method call.
Test: You should test several sets of data to make sure that your program is working correctly.
Although your main method may not use all the methods in Icosahedron, you should ensure that
all of your methods work according to the specification. You can use interactions in jGRASP or
you can write another class and main method to exercise the methods. The viewer canvas should
also be helpful, especially using the “Basic” viewer and the “toString” viewer for an Icosahedron
object. Web-CAT will test all of the methods specified above for Icosahedron to determine your
project grade.
General Notes
1. All input from the keyboard and all output to the screen should done in the main method. Only one
Scanner object on System.in should be created and this should be done in the main method. All
printing (i.e., using the System.out.print and System.out.println methods) should be in the main
method. Hence, none of your methods in the Icosahedron class should do any input/output (I/O).
2. When a method has a return value, you can ignore the return value if it is no interest in the current
context. For example, when setEdge(3.5) is invoked, it returns true to let the caller know the edge
field was set; whereas setEdge(-3.5) will return false since the edge field was not set. If the caller
knows that x is positive, then the return value of setEdge(x) can safely be ignored since it can be
assumed to be true.
3. Even though your main method may not be using the return type of a method, you can ensure that the
return type is correct using interactions.
