Homework 1C (CS 17/111/112/19): Lists and Mutation

In order to complete this assignment, you must have already completed HW1B. In this homework, we'll be building on top of classes that we've created in the previous homeworks, and you will need to copy your class implementations from previous assignments.

We will open this assignment for submission in Gradescope sometime Tuesday. We are still finishing configuring the autograder around the changed assignment contents.

Due: Friday, February 11th, 2022 at 11:59pm ET

Collaboration Policy: You may collaborate as much as you want on this assignment (this is more flexible than the normal course policy). The goal is to get everyone up to speed on functional programming. You are required to turn this in, but it will be weighted lightly in final grades. That said, we strongly encourage you to actively try writing these on your own while collaborating, as assignments after we come back together will assume you can do these sorts of problems on your own.

Learning Objectives

• To practice working with Java's built-in lists
• To practice structuring code around access modifiers
• To practice using Java types to control the ability to perform certain computations

Setup

Using this GitHub Classroom link, accept the assignment and clone on your machine.

If you're having trouble with IntelliJ, our First Time Setup Guide includes a common bugs/FAQ section.

Please make sure to read our Gradescope submission guide before handing in your assignment!

Style Expectations

For all future assignments, including this one, we expect your code to conform to the CS200 Java Style Guide.

Problems

In the last assignment, we created a GradeReport class. Now, it's time to set up the gradebook for an entire class, as well as the ability to manage (and update) grades. We also want to support Faculty teaching multiple courses.

More Courses

Task: Edit your Faculty class so that the field that stores what they are teaching could be a LinkedList of Course rather than a single Course. You'll have to update the constructor and perhaps other methods that worked on the previous field type as well.

If you need to check whether a specific Course object is in a faculty member's list of courses, use the LinkedList method contains which takes an object and returns a boolean.

Creating a Gradebook

Task: Add a gradebook field to the Course class. It should be of type LinkedList<GradeReport>. This field should be initialized to an empty list within the Course constructor.

Reminder that to use this, you will need the following import statement at the top of your Course.java:

import java.util.LinkedList;

Adding Grades

Task: Add a method named storeGrade to the Course class. The method should take in aStudent and a valid grade (LetterGrade or SNCGrade from assignment 1B). The method should result in updating the Course's gradebook to include a GradeReport for the corresponding student. You may assume that the student doesn't already have a grade in the Gradebook.

Looking up GradeReports

Task: Create a methodfindGradeReport in the Course class that takes the name of a student and returns the gradeReport of the named student in the course. The method should return null if the student is not in the course. Mark this method as private (replacing public with private at the start of the method header.)

Updating Grades

Task: Add a method named updateGrade to the Course class. The method should take in the name of a student (String) and a valid grade. The method should result in the new grade being stored in the gradebook for the given student. If the student does not have a grade, throw a RuntimeException with the message "no grade for student".

Note: Java has different kinds of exceptions for different kinds of errors. For now, we will use a RuntimeException for any error related to the logic of the program or system being represented (as opposed to IllegalArgumentException which we use when an input is not from an expected set of values).

throw new RuntimeException(<insert error message>);

Hint: Use previous problems as helpers!

Finding Students in a Gradebook

Task: Add a method called gradeLookup to the Course class. The method should take a Faculty or TA object and a student name as input.

• If gradebook has a GradeReport for the given student name, the method should return a String representation of the grade.
• If the given Faculty or TA is not teaching the course, throw a RuntimeException with the message "permission denied".
• If no such grade is found, a RuntimeException with the message "student <NAME> not found" should be thrown (where "<NAME>" is replaced with the student name being searched for).

In cases where both exceptions would apply, throw the permission denied exception.

Part of the point of the question is for you to think about how to take an argument that can be Faculty or TA, but not a general Student. (We've covered everything you need in order to do this. You may NOT use instanceOf).

Identifying Students in Trouble

Task: Add a method reportsWithC to the Course class. The method should return a list of GradeReport from the course gradebook in which the grade is the letter C.

The point of this question is for you to practice using good object-oriented code organization to check attribute of objects. You should NOT use getters to do this.

Note: In order to write this, you will need to be able to check whether two grades are the same. Lab 2 gave a quick introduction to writing equals methods, but IntelliJ will also generate equals methods for you automatically. If you start typing public boolean equals in a class, IntelliJ will give you a popup that asks whether it should generate "equals and hashcode methods". Click through doing that (just ignore or delete the generated hashcode method). You can also grab the equals methods by expanding the below spoiler arrow.

Equals methods for LetterGrade and SNCGrade

Note: you may have to edit the field names in these methods, depending on what you used in your class. Those edits would be in the last line of each of these methods.

For LetterGrade.java

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || this.getClass() != o.getClass()) return false;
        LetterGrade that = (LetterGrade) o;
        return this.grade == that.grade;
    }

For SNCGrade.java

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || this.getClass() != o.getClass()) return false;
        SNCGrade sncGrade = (SNCGrade) o;
        return this.pass == sncGrade.pass && this.passDistinction == sncGrade.passDistinction;
    }

Protecting Grade Information

Grade information is sensitive, and hence should be kept private. Other information may also be sensitive. Mark all of the fields in GradeReport, Student, Faculty, and Course as private. If this breaks some of your existing code, create additional methods as needed to restore your code to working.

Hint: Do this in stages: mark a couple of fields private and make sure your code will still run. Repeat until you've marked all of the fields. If you followed the "no getters" rule until now, your code should work without anything breaking.

You will learn about private annotations in lab this week. In a nutshell, marking a field private means that the field cannot simply be accessed from outside the class by writing object.field. Instead, you have to provide a method in the field's class that will perform the desired computation (you should not just hand the field out through a simple "getter" method, for those who already know that term).

Testing

Note: When writing your test suite, you should test only the methods we have asked you to write in this handout. Do not reference in your tests fields or methods that are not required by the assignment, or the autograder may fail.

Put your testing in the file Homework1CTest.java. You will submit this file to the Homework 1C (17/111/112/19): Testing assignment on Gradescope. See our gradescope submission guide for an explanation on how we are grading your tests, and how you can use the Testing assignment on Gradescope to get a better understanding of the assignment.

Task: Write a thorough set of tests for gradeLookup. We will grade your tests on this problem in particular detail. We will do this by using your tests to try to detect flawed solutions (that we have written). We will also run your tests on multiple good solutions, to make sure that your tests work on good solutions other than your own.

More on how we grade your tests

Edit Feb. 10: Tests will be graded manually this assignment, sorry for the confusion! Autograded wheats and chaffs will begin next assignment. We'll have a more detailed guide on how to deal with those soon after the assignment is released.
We are autograding your test suites by running it against a series of chaffs (bad implementations) of the solution to see if your testsuite catches the bugs in those implementations. You do not need to catch every chaff. Instead, we are looking to see if your tests are covering relevant areas of the code. The chaffs are labeled with what area of the code their bug is in, and we want to see that your tests are catching at least a few chaffs in most of these areas of the code. A chaff might have an incorrect arithmetic formula, return the wrong value in an if statement, make an assumption about inputs (such as an arbitrary string input only getting lowercase strings), and so on (this list isn’t exhaustive). Our goal in using chaffs is to help you get better at developing good sets of tests for programs.

Task: Develop a set of tests that check the expected interactions among storeGrade, updateGrade, gradeLookup, and reportsWithC. What do we mean? One might expect that namesWithC (for example) would return a different output after a call to updateGrade. Good test suites therefore test the interactions between methods when the changes made by one should affect (or not!) the output that comes from the other. We're asking you to develop a set of such interaction tests for these four functions.

Note: that you cannot test private methods in Homework1CTest.java (because the test class cannot "see" private methods). You may want to test that method before you make it private, but do not include tests for private methods in your Homework1CTest.java file.

Pro Tip: If you find that you need to set up the same courses, students, etc for multiple tests, you can write a single method to set up your data and tell JUnit to run it before each test method. Here's an example:

public class Homework1CTest {
  Course c1, c2;
  
  @Before
  public void setup() {
    this.c1 = new Course("VISA", 100, 1)
    this.c2 = new Course("HIST", 310, 1)
  }
  
  @Test
  public void testDept() {
    Assert.assertEquals(c1.department,"VISA");
  }
}

We create the variables for data as fields outside the methods. The @Before annotation tells JUnit to run that method before running every test. This way, your tests can focus just on the conditions to check, and you can set up the data just one time. This also restores the values of c1, etc before each test, in case you have a test that needs to modify your data.

Handing In

Begin by cloning the GitHub repository found by clicking the above GitHub Classroom link. The following files should be in the sol directory. You can move the files you wrote in 1B into this directory.

• Course.java containing public class Course
• Faculty.java containing public class Faculty
• Student.java containing public class Student
• Person.java containing public abstract class Person
• TA.java containing public class TA
• GradeReport.java containing public class GradeReport
• IGrade.java containing public interface IGrade
• Letter.java containing public enum Letter
• LetterGrade.java containing public class LetterGrade
• SNC.java containing public enum SNC
• SNCGrade.java containing public class
• Homework1CTest.java containing public class Homework1CTest
• TestRunner.java containing public class TestRunner
• AutograderCompatibility.java containing public class AutograderCompatibility

After completing this assignment, you should be ready to turn in (at least) the following solution files:

• Course.java containing public class Course
• Faculty.java containing public class Faculty
• Student.java containing public class Student
• Person.java containing public abstract class Person
• TA.java containing public class TA
• GradeReport.java containing public class GradeReport
• IGrade.java containing public interface IGrade
• Letter.java containing public enum Letter
• LetterGrade.java containing public class LetterGrade
• SNC.java containing public enum SNC
• SNCGrade.java containing public class SNCGrade
• Homework1CTest.java containing public class Homework1CTest

You may also include other classes, interfaces, and abstract classes.

Once you have handed in your homework, you should receive an email, more or less immediately, confirming that fact. If you don’t receive this email, try handing in again, or ask the TAs what went wrong.

Note: There should be a class in the stencil code named AutograderCompatibility. Using this class is required to ensure that your submission is working correctly with the autograder. You will be penalized if your code does not work with the autograder.

If Gradescope gives you message “The autograder failed to execute correctly. Please ensure that your submission is valid. Contact your course staff for help in debugging this issue. Make sure to include a link to this page so that they can help you most effectively," uncomment the main method of AutograderCompatibility and check that it compiles and runs. If it still doesn't work, come to hours or post on Ed for help.

Congratulations! You have just finished Homework 1. Now it is time for us to say goodbye, bye, bye. At least until next time.

FAQ

For examples of tests, see the Homework 1A FAQ. If you have other questions, feel free to post on Ed or come to hours.

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