Homework 3: Gradebook

Due October 8 @ 8:00pm on Autolab

• 1. Introduction
• 2. Your Tasks
  • 2.1. The Grade Class
  • 2.2. The Student Class
  • 2.3. The GradeBook Class
• 3. The Data File Format
• 4. Calculating the Course Average
• 5. Grading and Submission
• 6. Restrictions
• 7. Important Notes

1. Introduction

The purpose of this homework is to give you practice programming with your first real “data structure”, and an important one in Java, the ArrayList. You will also obtain practice writing and testing a class from scratch. In this homework, you will implement a simple gradebook for a course. Your gradebook will input a CSV file containing student information and assignment grades. The gradebook will consist, basically, of an ArrayList of Students. Each student will be an instance of the Student class, but you will have to augment the initial Student class with a private instance variable that can hold an ArrayList of grades. There are other, better, ways to store grades, but it will work for this assignment, the focus of which is on ArrayLists and their operations. You will also need to write the Grade class.

Download a pre-prepared Eclipse Project hw3.zip and import it into Eclipse using these instructions. You will make all of your changes inside of the java files in this project.

2. Your Tasks

There are a variety of tasks for this homework.

2.1. The Grade Class

The Grade class will represent and store information about a single grade. A grade has two components: a name (stored as a String, e.g., HW1) and the actual grade for that assignment (stored as an int). You will need to write a constructor for this class as well as a few methods, such as getters and setters.

2.2. The Student Class

Included with this assignment is a pre-existing Person class. Since a student is-a person, you should use inheritance when creating the Student class. A student is a person who also has an andrew ID, a major, and an ArrayList of grades. You will also need to write a variety of other methods for Student as needed. Those methods are not described in detail here, you will need to figure out on your own exactly what you need.

2.3. The GradeBook Class

You will need to write the following methods in the GradeBook class. With the exception of the constructor, most GradeBook methods should be very short, as anything that involves an individual Student should be a method in the Student class, called on the appropriate Student from the GradeBook.

• GradeBook(String fileName)
  This constructor needs to be modified to work with the given file format. In particular, you will need to decide how to incorporate the reading of the grades. A suggestion would be to read the file a line at a time, parse the line into tokens and loop over the grade-name/grade-value pairs. You may assume that the file is well-formatted, i.e., each line contains a first name, last name, andrewID, and a number of grade-name/grade-value pairs. You will also have to decide how to get the grades into the ArrayList of Grades that you will have to add to the Student class. I would suggest building a Student with the names and id and then create a method called addGrade inside Student to add each grade to the appropriate instance variable of the Student object.

• Student findStudent(String id)
  This method is optional, but you will almost certainly want it to help you in building other methods. It returns the Student corresponding to the andrew ID provided. If there is no student with that andrew ID, it returns null.

• String[] getIds()
  Returns an array of the andrew IDs of all students in the gradebook.

• String[] getIds(String major)
  Returns an array of the andrew IDs of all students with major in the gradebook.

• boolean dropStudent(String id)
  Drops the student with the given andrew ID from the gradebook. Returns true if successful and false otherwise.

• int getGrade(String id, String assignment)
  Returns the grade of the assignment for the student with the given andrew ID. If the student or assignment could not be found, it returns -1.

• boolean addGrade(String id, String assignment, int grade)
  Adds a grade to a the student with the given andrew ID. Returns true if successful and false otherwise.

• boolean changeGrade(String id, String assignment, int newGrade)
  Change a grade of the student with the given andrew ID. Returns true if successful and false otherwise.

• boolean writeDb(String filename)
  Writes the gradebook to the specified file in the correct CSV format. Returns true if successful and false otherwise.

• double getAverage(String id)
  Returns the current course average for the specified student. Returns -1 if the student could not be found or had no grades. See the section below entitled “Calculating the Course Average” for more details about computation of this value.

• String getAverageLetter(String id)
  Returns the current course average for the specified student, but as a letter grade. (A, B, C, D, R). Apply the standard 90 and above is A, 80 to 90 is B, etc. Returns null if the student could not be found or had no grades.

• String toString()
  Needs to correctly return a properly formatted String that represents the contents (the roster) of the gradebook. Properly formatted, in this case, means following the same format convention of the input file. This method is provided for you in GradeBook, but it relies on a functional toString in Student, which is not provided.

3. The Data File Format

The input (and output) files that your program should be able to work with have a comma separated value (CSV) format. Each line the file contains the information for one contact, with each field of that contact separated by a comma. The fields are:

First Name, Last Name, Age, Major, andrew ID, Grade Pairs, ...

Each “grade pair” consists of the name of the grade (homework, quiz, etc.) followed by the actual grade for that assignment. To keep things simple, assume you have only 4 categories of grades, formatted as follows: homeworks (HWn), quizzes (Qn), midterm (M) and Final (F). Note that there is not a specific number of grades per student, it could vary.

The provided Eclipse project includes some sample files that you can use for testing. (Looking at them will also help you make sure you understand the file format.)

4. Calculating the Course Average

The gradebook in this assignment will calculate the grade using the same percentages we are using for the course:

The formula you will use to determine the current course average is, thus:

\(avg = \frac{HW_{avg} * 40 + Quiz_{avg} * 15 + Midterm * 20 + Final * 25}{40 + 15 + 20 + 25}\)

However, if some category of grade is missing entirely, then you need to remove it completely from the calculation. For example, if you have quiz, homework, and midterm scores available but no final exam, then you would use…

\(avg = \frac{HW_{avg} * 40 + Quiz_{avg} * 15 + Midterm * 20}{40 + 15 + 20}\)

Let’s consider a practical example:
Darrel,Haley,23,Biology,dhaley,Q1,100,HW1,95,Q2,85

Darrel has some quiz and homework scores, but no midterm or final exam scores. His homework average is 95 (because there’s only one homework). His quiz average is 92.5. Therefore, his current course average is:

\(avg = \frac{95 * 40 + 92.5 * 15}{40 + 15} = 94.3181818\overline{18}\)

5. Grading and Submission

There are two parts of the grading of this assignment:

1. For the first 70 points, your submission will be auto-graded on Autolab.
2. For the next 30 points, your submission will be manually graded to check for things like style, implementation methodology, and the testcases you include in the main method.

You will submit your program to Autolab. Login to the system and you will see the homework.

For this homework, because there are two files, you’ll need to submit a zip file containing your code. Luck for you, however, Eclipse can create this zip file for you. Check out these instructions. On Autolab, you’ll submit that exported zip file. On the page that follows your submission you will see your live score (out of 70). It may take up to a few minutes for your score to appear, during that time just hit refresh in your browser. If you receive a lower score than you expect, you can click on the score to see the feedback from the autograder.

6. Restrictions

You may only use the following Java libraries in this assignment:

java.io.FileReader
java.io.PrintWriter
java.util.ArrayList
java.util.Arrays
java.util.Scanner

7. Important Notes

• If you have questions, please post to Piazza. The course staff, including the instructor, monitor and answer questions there.
• When posting to Piazza, if you include any code make sure your question is posted privately to the instructors, and not to the entire class.
• Do not change the names of any of the provided methods or files.
• After you submit to Autolab, make sure you check your score. If you aren’t sure how to do this, then ask.
• There is no partial credit on Autolab testcases. Your Autolab score is your Autolab score.
• Read the last bullet point again. Seriously, we won’t go back later and increase your Autolab score for any reason. Even if you worked really hard and it was only a minor error…
• You can submit to Autolab multiple times. So, after you submit you should check your score. If it isn’t a 70 you can keep working until it is.
• Don’t forget to make sure your code conforms to the style guide. We’ll be taking a look at that!
• Don’t forget to write your own testcases that go beyond the provided testcases. We’ll be taking a look at those!