Description
Overview: In this project, the two files developed in Part 1 are to be extended as follows: (1)
TriangularPrism, which is a class representing a TriangularPrism object, will implement the
Comparable interface and (2) TriangularPrismTest class, which is a JUnit test class, will be expanded
from method coverage to condition coverage for TriangularPrism. The new items for Part 2 are
underlined below for your convenience. Note that there is no requirement for a class with a main
method in this project.
You should create a new folder to hold the files for this project and add your files from Part 1
(TriangularPrism.java file and TriangularPrismTest.java). You should create a new jGRASP project
for Part 2 and add TriangularPrism.java file and TriangularPrismTest.java to the project; you should
see the two files in their respective categories – Source Files and Test Files. If
TriangularPrismTest.java appears in source File category, you should right-click on the file and select
“Mark As Test” from the right-click menu. You will then be able to run the test file by clicking the
JUnit run button on the Open Projects toolbar.
• TriangularPrism.java (new items for this class in Part 2 are underlined)
Requirements: Create a TriangularPrism class that stores the label, triangle edge, and prism
height (edge and height are non-negative, >= 0). The TriangularPrism class also includes
methods to set and get each of these fields, as well as methods to calculate the triangle area,
rectangle area, surface area, and volume of a TriangularPrism object, and a method to provide a
String value that describes a TriangularPrism object. The TriangularPrism class includes a one
static field (or class variable) to track the number of TriangularPrism objects that have been
created, as well appropriate static methods to access and reset this field. And finally, this class
provides a method that JUnit will use to test TriangularPrism objects for equality as well as a
method required by Checkstyle. In addition, TriangularPrism must implement the Comparable
interface for objects of type TriangularPrism.
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A uniform TriangularPrism is a TriangularPrism in which the faces (bottom and top) are equilateral
triangles (a = b = c) with side edge length a. When lying on a triangle face, the prism has height h.
The sides of the prism are three rectangles of the same size. (https://en.wikipedia.org/wiki/Triangular_prism)
The variables are
abbreviated as follows:
� is triangle edge length
� is height of prism
�� is triangle area
�� is rectangle area
A is total surface area
V is volume
�# = 0.25*3�$
�% = �ℎ
� = 2�# + 3�%
� = �#ℎ
Design: The TriangularPrism class implements the Comparable interface for objects of type
TriangularPrism and has fields, a constructor, and methods as outlined below (last method is
new).
(1) Fields: Instance Variables – label of type String, edge of type double, and height of type
double. Initialize the String to “” and the double variables to 0 in their respective
declarations. These instance variables should be private so that they are not directly
accessible from outside of the TriangularPrism class, and these should be the only instance
variables (fields) in the class.
Class Variable – count of type int should be private and static, and it should be initialized to
zero.
(2) Constructor: Your TriangularPrism class must contain a public constructor that accepts three
parameters (see types of above) representing the label, edge, and height. Instead of assigning
the parameters directly to the fields, the respective set method for each field (described
below) should be called since they are checking the validity of the parameter. For example,
instead of using the statement label = labelIn; use the statement
setLabel(labelIn); The constructor should increment the class variable count each
time a TriangularPrism is constructed.
Below are examples of how the constructor could be used to create TriangularPrism 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.
TriangularPrism ex1 = new TriangularPrism(“Small Example”, 1.8, 3.25);
TriangularPrism ex2 = new TriangularPrism(” Medium Example “, 10.7, 25.4);
TriangularPrism ex3 = new TriangularPrism(“Large Example”, 45.47, 105.0);
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(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 TriangularPrism, which should each be public, are described below. See the
formulas in the figure above and the Code and Test section below for information on
constructing these methods.
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 getEdge: Accepts no parameters and returns a double representing the edge field.
o setEdge: Takes a double parameter and returns a boolean. If the double
parameter is non-negative, then the parameter is set to the edge field and the method
returns true. Otherwise, the method returns false and the edge field is not set.
o getHeight: Accepts no parameters and returns a double representing the height
field.
o setHeight: Takes a double parameter and returns a boolean. If the double
parameter is non-negative, then the parameter is set to the height field and the method
returns true. Otherwise, the method returns false and the height field is not set.
o triangleArea: Accepts no parameters and returns the double value for the area of
one of the triangular faces of the prism.
o rectangleArea: Accepts no parameters and returns the double value for area of
one of the rectangle sides of the prism.
o surfaceArea: Accepts no parameters and returns the double value for the total
surface area of the TriangularPrism.
o volume: Accepts no parameters and returns the double value for the volume of the
TriangularPrism.
o toString: Returns a String containing the information about the TriangularPrism
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 within the String but it should not begin or end with a newline. In addition to the
field values (or corresponding “get” methods), the following methods should be used to
compute appropriate values in the toString method: rectangleArea(),
triangelArea(), and surfaceArea(), and volume(). Each line should have
no trailing spaces (e.g., there should be no spaces before a newline (\n) character). The
toString value for ex1, ex2, and ex3 respectively are shown below (the blank lines
are not part of the toString values).
TriangularPrism “Small Example” with triangle edge of 1.8 units
and prism height of 3.25 units has:
triangle area = 1.403 square units
rectangle area = 5.85 square units
surface area = 20.356 square units
volume = 4.56 cubic units
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TriangularPrism “Medium Example” with triangle edge of 10.7 units
and prism height of 25.4 units has:
triangle area = 49.576 square units
rectangle area = 271.78 square units
surface area = 914.491 square units
volume = 1,259.221 cubic units
TriangularPrism “Large Example” with triangle edge of 45.47 units
and prism height of 105.0 units has:
triangle area = 895.263 square units
rectangle area = 4,774.35 square units
surface area = 16,113.576 square units
volume = 94,002.595 cubic units
o getCount: A static method that accepts no parameters and returns an int representing
the static count field.
o resetCount: A static method that returns nothing, accepts no parameters, and sets the
static count field to zero.
o equals: An instance method that accepts a parameter of type Object and returns false if
the Object is a not a TriangularPrism; otherwise, when cast to a TriangularPrism, if it has
the same field values as the TriangularPrism upon which the method was called, it returns
true. Otherwise, it returns false. Note that this equals method with parameter type Object
will be called by the JUnit Assert.assertEquals method when two TriangularPrism objects
are checked for equality.
Below is a version you are free to use.
public boolean equals(Object obj) {
if (!(obj instanceof TriangularPrism)) {
return false;
}
else {
TriangularPrism d = (TriangularPrism) obj;
return (label.equalsIgnoreCase(d.getLabel())
&& (Math.abs(edge – d.getEdge()) < .000001)
&& (Math.abs(height – d.getHeight()) < .000001));
}
}
o hashCode(): Accepts no parameters and returns zero of type int. This method is
required by Checkstyle if the equals method above is implemented.
o compareTo: Accepts a parameter of type TriangularPrism and returns an int as
follows: a negative value if this.volume() is less than the parameter’s volume; a
positive value if this.volume() is greater than the parameter’s volume; zero if the
two volumes are essentially equal. For a hint, see the activity for this module.
Code and Test: As you implement the methods in your TriangularPrism class, you should
compile it and then create test methods as described below for the TriangularPrismTest class.
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• TriangularPrismTest.java
Requirements: Create a TriangularPrismTest class that contains a set of test methods to test each
of the methods in TriangularPrism. The goal for Part 2 is method, statement, and condition
coverage.
Design: Typically, in each test method, you will need to create an instance of TriangularPrism,
call the method you are testing, and then make an assertion about the expected result and the
actual result (note that the actual result is commonly the result of invoking the method unless it
has a void return type). You can think of a test method as simply formalizing or codifying what
you could be doing in jGRASP interactions to make sure a method is working correctly. That is,
the sequence of statements that you would enter in interactions to test a method should be entered
into a single test method. You should have sufficient test methods so that each method,
statement, and condition in TriangularPrism are covered. Collectively, these test methods are a
set of test cases that can be invoked with a single click to test all of the methods in your
TriangularPrism class.
Code and Test: A good strategy would be to begin by writing test methods for those methods in
TriangularPrism that you “know” are correct. By doing this, you will be able to concentrate on
the getting the test methods correct. That is, if the test method fails, it is most likely due to a
defect in the test method itself rather the TriangularPrism method being testing. As you become
more familiar with the process of writing test methods, you will be better prepared to write the
test methods as new methods are developed. Be sure to call the TriangularPrism toString
method in one of your test methods and assert something about the return value. If you do not
want to use assertEquals, which would require the return value match the expected value exactly,
you could use assertTrue and check that the return value contains the expected value. For
example, for TriangularPrism example3:
Assert.assertTrue(example3.toString().contains(“\”Large Example\””));
Also, remember that you can set a breakpoint in a JUnit test method and run the test file in Debug
mode. Then, when you have an instance in the Debug tab, you can unfold it to see its values or
you can open a canvas window and drag items from the Debug tab onto the canvas. You can also
step-in to the method being called by the test method and then single-step through it, looking for
the error.
The Grading System
When you submit TriangularPrism.java and TriangularPrismTest.java, the grading system will use the
results of your test methods and their level of coverage of your source files as well as the results of our
reference correctness tests to determine your grade. In this project, your test file should provide method,
statement, and condition coverage. Each condition in your source file must be exercised both true and
false. See the note below for hints on testing the equals.
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Note For Testing the equals Method
Perhaps the most complicated method to test is the equals method in TriangularPrism. This method has
three conditions in the boolean expression that are &&’d. Since Java (and most other languages) uses
short-cut logic, if the first condition in an && is false, the &&’d expression is false. This means that to
test the second condition, the first conditions must be true. Furthermore, to test the third conditions both
the first and second conditions must be true. To have condition coverage for the equals method, you need
the four test cases where the three conditions evaluate to the following, where T is true, F is false, and X
is don’t care (could be true or false):
FXX – returns false
TFX – returns false
TTF – returns false
TTT – returns true
