Java Student Ext (Inheritance)

Topic

Inheritance
Method Overriding

Description

Write a program that will compute and display the final grades for a list of students. A student's final grade is determined from the scores obtained in the class exams. Each student in the class may be given a different number of exams as determined by the instructor. The final grade is determined by the average of the scores in all the exams given.

This program is an enhancement of a previous exercise that did the same. However, this exercise will additionally provide for assigning a CR or NCR (Credit or No Credit) grade.

For each student, the program will input student id, name, the number of exams given and scores in each of the exams.

Additionally, it will input the grade type: "Letter" or Credit. The grade type of Letter will indicate that student will receive a grade of A, B, C, D, or F. The grade type of Credit will indicate that the student will receive a grade of CR or NCR.

The scores in each of the exams will vary from 0 to 100. Each exam will carry the same weight. The final grade will be computed by taking the average of the scores in all the exams given (i.e. by adding the scores in all the exams and dividing it with the number of exams given). The final grade will be assigned depending upon the percentage of total points in the exams given as follows:

A – 90 to 100%
B – 80 to 89%
C – 70 to 79%
D – 60 to 69%
F – 0 to 59%

Additionally, for a grade type of Credit, the grade will be determined as follows:

If the student qualifies for a C or better grade, the student will be assigned a CR (Credit) grade. Otherwise, the student will be assigned an NCR (No Credit) grade.

Instructions

Use a String variable for keeping final grade.
Use a String variable for keeping grade type.

Comparing Strings

For comparing two Strings for equality, use one of the following two String methods:
equals
equalsIgnoreCase

Implementation

For this assignment create the following classes.

Student class

Create a class Student that provides the following:

• Private instance variables for holding student id (int), name (String), exam scores (an int array).
• A public constructor with parameters for initializing student id (int), name (String) and exam scores. The exam scores are passed as an array of int.
• A public method for returning the final grade.
• Accessor (getter) methods for getting student id, name, exam scores .

Instead of rewriting this class, you may copy the contents of the same class from a previous exercise.

StudentExt class.

Create a class StudentExt that extends the class Student above. This class will extend the class Student in order to provide additional functionality for assigning a CR or NCR grade.

The class will provide the following:

• A private String instance variable gradeType for indicating the grade type (Letter or Credit). The variable gradeType will record "Letter" for a letter grade type and Credit for Credit/No Credit grade type.
• A public constructor for initializing student id (int), name (String), exam scores (an int array) and grade type (String). This constructor will call the parent class constructor for initializing student id, name and exam scores. It will initialize the grade type itself directly.
• A public method for returning the final grade. This method will over ride the parent class method used for computing the grade. This method will have the same name and the same parameter profile as the parent class method. This new method will call the parent class method (of the same name) to compute the student letter grade. After return from the parent class method, in the case of grade type "Credit", it will change the letter grade returned by the parent class method to either CR or NCR.

TestStudentExt class

Write a class TestStudentExt containing the main method. The method main will do the following:

• Prompt the user to enter the total number of students (say n).
• Create an array of n references (for holding n StudentExt object references). (The StudentExt objects will be created in the next step).
• Create n StudentExt objects. Do this by setting up an n count loop. In each pass through the loop, do the following:
  a. Ask the user to enter data for one student.
  b. Create a StudentExt object and initialize it with data provided by the user. Store the object reference in the array of StudentExt references created above.

• Display the student results by grade type. First display students receiving grade A, followed by those receiving B, followed by those receiving C, followed by those receiving D, followed by those receiving F, followed by those receiving Cr, followed by those receiving NCR.

You may do this in a number of ways including the following:

Method I.

Create seven empty Strings, outA, outB, outC, outD, outF, outCr, outNcr. Use the String outA for storing output relating to A students; use String outB for storing output relating to B students; etc. Use the object accessor methods to access object values as needed. At the end, prepare a String out that concatenates all the above seven Strings. Then display the String out.

Method II.

Create a String array out of 7 Strings. Use out [0] for accumulating output relating to A students, out[1] for B students etc. Write a static method displayRestult to display output. Call the static method displayResult and pass it the array out.

displayResult

For method II above, write a static method displayResult. This method will receive a String array and display the contents of all elements of the String array one by one. Here is a proposed header for the method:

public static void displayResult (String [ ] s)
{
}

It is suggested that you use method II.

You may use the class TestStudent from a previous exercise and modify it to create this class TestStudentExt.

Testing

Input

Use the following test data for input.

1, John Adam, 3, 93, 91, 100, Letter
2, Raymond Woo, 3, 65, 68, 63, Letter
3, Rick Smith, 3, 50, 58, 53, Letter
4, Ray Bartlett, 3, 62, 64, 69, Letter
5, Mary Russell, 3, 93, 90, 98, Letter
6, Andy Wong, 3, 89,88,84, Letter
7, Jay Russell, 3, 71,73,78, Letter
8, Jimmie Wong, 3, 70,77,72, Letter
9, Jackie Chan, 3, 85,89,84, Letter
10, Susan Wu, 3, 80,88,84, Letter
11, Bruce Lee, 4, 74, 79, 72, 75, Credit
12, Chuck Norris, 5, 63, 64, 62, 60, 68, Credit
13, Jet Li, 3, 85, 83, 89, Credit
14, Jessica Lauser, 3, 82, 84, 87, Letter
15, Mahnoosh Nik-Ahd, 2, 98, 99, Letter

In the above data, for the first entry, id is 1, name is John Adam, exam scores are 93, 91, 100 and grade type is letter grade.

Output

1 John Adam (A)
5 Mary Russell (A)
15 Mahnoosh Nik-Ahd (A)
6 Andy Wong (B)
9 Jackie Chan (B)
10 Susan Wu (B)
14 Jessica Lauser (B)
7 Jay Russell (C)
8 Jimmie Wong (C)
2 Raymond Woo (D)
4 Ray Bartlett (D)
3 Rick Smith (F)
11 Bruce Lee (CR)
13 Jet Li (CR)
12 Chuck Norris (NCR)

Sample Code

The method findGrade below over rides the parent method findGrade. Internally, it also calls the parent method findGrade for finding the student's letter grade. On return from the parent method, in the case of a gradeType of "CR", it reassigns the grade to be CR or NCR depending upon the students letter grade as described below:

For a gradeType of "Credit", if the student's letter grade is A, B, or C, it reassigns the grade to be CR and otherwise (for a letter grade of D or F) it reassigns it to be NCR.

public String findGrade ( )
{
String grade = super.findGrade ( );
if (gradeType.equalsIgnoreCase ("Credit"))
{
if ( (grade.equalsIgnoreCase ("A")) ||
(grade.equalsIgnoreCase ("B")) ||
(grade.equalsIgnoreCase ("C")))
grade = "CR";
else
grade = "NCR";
}
return grade;
}