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Introduction to Software Development
Homework 6: Movie Trivia
(Deadline as per Canvas)
This homework deals with the following topics:
● More experience with class-based object-oriented programming
● Arrays and ArrayLists
● Test-Driven Development (unit testing)
● Static methods (we’ll learn about these in the next lecture)
The Assignment
In this HW, we will deal with representing a movie database using classes and arraylists, with
the goal of answering some simple movie trivia questions. For example, “what is the name of
the movie that both Tom Hanks and Leonardo DiCaprio acted in?”. Or, “what are the movie
ratings for Rocky I?”
To represent the movie database, we will use 2 ArrayLists: The first corresponds to information
about an actor and all the movies that he/she has acted in. The second corresponds to
information about the critics score and the audience score from
https://www.rottentomatoes.com/, about different movies.
Given that information, we will then want to answer some typical movie trivia questions.
Data Structures
There are two ArrayLists in this HW: The first ArrayList stores Actors (instances of the Actor
class) with the name of the actor and a list of movies the actor has acted in. The second
ArrayList stores Movies (instances of the Movie class) with the name of the movie, the critics
rating, and the audience rating.
The two ArrayLists are populated with data from two different data files. The ArrayList with
the information about actors is loaded from the “moviedata.txt” file. Each row in the file
contains an actor’s name followed by movies the actor has acted in. For example:
Meryl Streep, Doubt, Sophie's Choice, The Post
The ArrayList with information about movies is loaded from the “movieratings.csv” file. Each
row in the file contains a movie followed by the critics rating and the audience rating. For
Introduction to Software Development
example:
Doubt,79,78
The code for loading the data files is provided for you in the MovieDB.java file, but here are
some items to note:
● When loading the data files, the code converts all characters to lowercase and trims
the whitespace before and after each column of data before storing the information in
an ArrayList. For example:
○ “Meryl Streep” or “ meryl streep ” is converted to “meryl streep”
○ “Sophie’s Choice” or “ sophie’s choice ” is converted to “sophie’s choice”
● The actor names in “moviedata.txt” are unique and the movie names in
“movieratings.csv” are unique.
● Actors may have no movies. For example, in “moviedata.txt”, there are no movies listed
for “Brandon Krakowsky”. He may not have been casted in a movie (yet!), but we must
allow him to keep his dream, right? In this case, the code converts this line into an
instance of the Actor class, with a name and an empty list of movies.
● The critics and audience ratings in “movieratings.csv” are between 0 and 100 and
always exist.
Starter Code
We have provided you with four main Java class files for the program: MovieDB.java,
Actor.java, Movie.java, and MovieTrivia.java. The MovieDB class reads from the two text files,
“moviedata.txt” and “movieratings.csv”, and populates two ArrayLists with the data using the
Actor class and the Movie class. The MovieTrivia class controls the overall program and will
provide methods for asking different kinds of movie trivia questions, and insert new actors and
movie ratings into the movie database. We’ve also provided you with MovieDBTest.java to run
some very basic tests against MovieDB.java and MovieTriviaTest.java to run some tests against
MovieTrivia.java.
Download all of the provided files and put the Java files in the “src” folder of a new Java
project, keeping the exact same file and package structure. If there are no packages in your
Java project, please create them using “New Package” in Eclipse. Keep the .txt and .csv files
Introduction to Software Development
outside of the “src” folder in the Java project. You might also have to add the Junit 5 library to
your build path. The final structure of the project in the package explorer should look like this:
Once the project is set up, run MovieDBTest.java to make sure the data files can be loaded and
the initial tests pass. If there are any issues with the testing file, please let us know ASAP. You
should also run MovieTrivia.java to make sure the main program runs. After running
MovieTrivia.java, you should see the actors and movies information printed to the console (see
below).
Line 1:
[Name: meryl streep Acted in: [doubt, sophie's choice, the post],
Name: tom hanks Acted in: [the post, catch me if you can, cast away],
Name: amy adams Acted in: [doubt, leap year, man of steel, arrival],
Name: brandon krakowsky Acted in: [], Name: robin williams Acted in:
[popeye], Name: brad pitt Acted in: [seven, fight club]]
Line 2:
[Name: doubt Critic Rating: 79 Audience Rating: 78, Name: arrival
Critic Rating: 94 Audience Rating: 82, Name: jaws Critic Rating: 97
Audience Rating: 90, Name: rocky ii Critic Rating: 91 Audience
Rating: 95, Name: seven Critic Rating: 29 Audience Rating: 29, Name:
popeye Critic Rating: 0 Audience Rating: 0, Name: et Critic Rating:
85 Audience Rating: 86]
Introduction to Software Development
Suggested Approach
Try doing this homework using the test-driven development (TDD) approach. In particular,
once you have run the starter code in MovieTrivia.java successfully, do not worry about writing
any additional code in the main method. Instead, implement the code (within the required
methods) in MovieTrivia.java so that it passes the test cases in MovieTriviaTest.java. As you
write additional test cases in MovieTriviaTest.java, you’ll implement additional code in
MovieTrivia.java so that it passes the test cases you’ve created. Once you’ve passed all test
cases, then make sure your method has good style. If not, refactor as needed, then rerun your
test cases.
After you finish this process for the first method, do the same for the second method, then the
third, etc.
Required Methods:
The “Utility Methods” and “More Fun Methods” described below must be implemented within
the MovieTrivia.java class.
Utility Methods
The first step is to create some basic utility methods for interacting with the database. You are
allowed (and encouraged) to modify the “moviedata.txt” and “movieratings.csv” files. Feel free
to add more movies, actors, ratings, etc. But if you prefer to leave these two input files
unaltered, you are free to do that as well. If you do decide to edit “moviedata.txt” or
“movieratings.csv”, please note that you may also need to modify some test cases in
MovieTriviaTest, since the expected values in some of the test cases may no longer apply.
As you’ll see, the ArrayList variables are passed to the individual methods as parameters. It is
possible that an ArrayList other than the ones created by the MovieDB class will be passed to
your methods. In fact, you can be guaranteed that the unit tests we write for checking your
methods will use different data. Our unit tests will be in accordance with the formatting
specified, but will have different values.
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Here is the list of 5 utility methods that we want you to write. Be sure to add javadocs to your
methods and comments to your code.
public void insertActor (String actor, String [] movies, ArrayList actorsInfo)
● Inserts given actor and his/her movies into database
○ The actorsInfo is the ArrayList that is to be inserted into/updated
○ actor is the actor name as a string
○ movies is a String array of movie names that the actor has acted in
● Note that while this method is called “insertActor”, it should actually do an insert or an update
○ If the given actor is not already present in the given actorsInfo arraylist, this method
should append the given actor along with their given movies to the end of actorsInfo.
○ If the given actor is already present in the given actorsInfo arraylist, it should append
the given movies to the end of the actor object's movieCasted list.
○ This method does not need to insert or update movies in the moviesInfo arraylist.
● This method does not return anything. It will work by just modifying the given actorsInfo
ArrayList passed to it
● Consider different kinds of input when writing your test cases in MovieTriviaTest.java for this
method. For example:
○ When inserting a new actor add the new instance of the Actor class to the end of the
ArrayList actorsInfo. When the actor already exists, update the actor’s movies in the
Actor class by adding the movies in the movies Array to the end of their list. When a
movie in the movies Array already exists in the actor’s list of movies, avoid adding a
duplicated one. Otherwise, add this movie to the actor’s list.
○ Actor names should not be case sensitive, but spelling must be correct. For example,
“Tom Hanks” and “ToM hanKS” should be considered the same actor in the database, so
when you try to insert an actor with the same name, but different case, it should
recognize it as already existing in the database. The same logic applies to every movie
in the movies Array.
○ Try inserting an actor with leading or trailing whitespace (e.g. “Bradley Cooper “) --
the whitespace should not make a difference. For example, “Bradley Cooper “ and
“Bradley Cooper“ should be considered the same actor in the database. The same logic
applies to every movie in the movies Array.
○ Keep the format in actorsInfo, for example, when actor is “Brad PITT” and movies are [“
Inglourious Basterds ”, “ONCE Upon A Time in Hollywood”], when
Introduction to Software Development
added to the database, they should be stored in the format of “brad pitt” and
[“inglourious basterds”, “once upon a time in hollywood”]. Please refer to the
description in the Data Structures section for detailed formatting information.
public void insertRating (String movie, int [] ratings, ArrayList moviesInfo)
● Inserts given ratings for given movie into database
○ The moviesInfo is the ArrayList that is to be inserted into/updated
○ movie is the movie name as a string
○ ratings is an int array with 2 elements: the critics rating at index 0 and the audience
rating at index 1
● This method should update the ratings for a movie if the movie is already in the database
● Consider different kinds of user input when writing your test cases. For example:
○ Create an instance of the Movie class for a new movie and append to the end of
moviesInfo or update the critics and audience scores for an existing movie in moviesInfo
○ The movie should not be case sensitive, but spelling must be correct. For example,
“Rocky ii” and “Rocky II” should be considered the same movie in the database.
○ A movie with leading or trailing whitespace (e.g. “ Arrival “)
○ An incorrect number in ratings or missing ratings. If ratings == null or ratings.length !=
2, do nothing and return. If the critics rating or audience rating is less than 0 or greater
than 100, do nothing and return. Neither of the ratings gets updated.
public ArrayList selectWhereActorIs (String actor, ArrayList actorsInfo):
● Given an actor, returns the list of all movies
○ actor is the name of an actor as a String
○ actorsInfo is the ArrayList to get the data from
● Given a non-existent actor, this method should return an empty list
● Consider different kinds of user input when writing your test cases. For example:
○ Non-existent actors. When the actor is non-existent, return an empty list.
Introduction to Software Development
○ Actor names should not be case sensitive, but spelling must be correct. For example,
“Tom Hanks” and “ToM hanKS” should be considered the same actor in the database.
○ Actor names with leading or trailing whitespace. For example, “Bradley Cooper “ and
“Bradley Cooper“ should be considered the same actor in the database.
public ArrayList selectWhereMovieIs (String movie, ArrayList actorsInfo):
● Given a movie, returns the list of all actors in that movie
○ movie is the name of a movie as a String
○ actorsInfo is the ArrayList to get the data from
● Given a non-existent movie, this method should return an empty list
● Consider different kinds of user input when writing your test cases. For example:
○ Non-existent movies
○ Movie names should not be case sensitive, but spelling must be correct. For example,
“Rocky ii” and “Rocky II” should be considered the same movie in the database.
○ Movie names with leading or trailing whitespace (e.g. “ Arrival “). For example, “
Arrival “ and “Arrival“ should be considered the same movie in the database.
public ArrayList selectWhereRatingIs (char comparison, int targetRating, boolean isCritic,
ArrayList moviesInfo)
● This useful method returns a list of movies that satisfy an inequality or equality, based on the
comparison argument and the targeted rating argument
○ comparison is either ‘=’, ‘>’, or ‘< ‘ and is passed in as a char
○ isCritic is a boolean that represents whether we are interested in the critics rating or the
audience rating. true = critic ratings, false = audience ratings.
○ targetRating is an integer
● Given incorrect input (e.g.) targetRating out of range of 0 <= targetRating <= 100) or
comparison is not ‘=’ or ‘<’ or ‘>’, this method should return an empty list
● Some examples of expected output are:
○ selectWhereRatingIs(‘>’, 0, true, moviesInfo) should return every movie in the database,
assuming no movie has a critic rating equal to 0.
○ selectWhereRatingIs(‘=’, 65, false, moviesInfo) should return every movie that has an
audience rating of exactly 65.
Introduction to Software Development
○ selectWhereRatingIs(‘<’, 30, true, moviesInfo) should return every movie that has a
critic rating less than 30. Basically the ones the critics hated!
● Consider different kinds of user input when writing your test cases. For example:
○ when comparison is non-existent (e.g. ‘?’), return an empty list.
○ when targetRating that is out of range, return an empty list.
More Fun Methods
Outside of the 5 utility methods above, we would like to be able to answer some other
interesting movie trivia questions and hence these other 5 methods are required. Remember
code reuse when you write these methods!
public ArrayList getCoActors (String actor, ArrayList actorsInfo):
● Returns a list of all actors that the given actor has ever worked with in any movie
except the actor herself/himself. You may think of how to use the 5 basic utility
methods implemented previously.
○ actor is the name of an actor as a String
○ actorsInfo is the ArrayList to search through
● Consider different kinds of user input when writing your test cases. For example:
○ Existing actors and non-existent actors (return an empty ArrayList)
○ Actor names should not be case sensitive, but spelling must be correct. For
example, “AMY ADAms” and “Amy Adams” should be considered the same
actor in the database.
○ Actor names with leading or trailing whitespace (e.g. “ Sylvester Stallone
“). For example, “Bradley Cooper “ and “Bradley Cooper“ should be considered
the same actor in the database.
public ArrayList getCommonMovie (String actor1, String actor2, ArrayList
actorsInfo):
● Returns a list of movie names where both actors were cast. You may think of how to
use the 5 basic utility methods implemented previously.
○ actor1 and actor2 are actor names as Strings
○ actorsInfo is the ArrayList to search through
Introduction to Software Development
● In cases where the two actors have never worked together, this method returns an
empty list
● Consider different kinds of user input when writing your test cases. For example:
○ Existing actors and non-existent actors. When actor1 or actor2 is non-existent,
there should be no movies in common.
○ Actor names should not be case sensitive, but spelling must be correct. For
example, “AMY ADAms” and “Amy Adams” should be considered the same
actor in the database.
○ Actor names with leading or trailing whitespace (e.g. “ Sylvester Stallone
“) For example, “Bradley Cooper “ and “Bradley Cooper“ should be
considered the same actor in the database.
○ actor1 and actor2 can be the same, in this case, return an ArrayList of movie
names that this actor was cast in.
public ArrayList goodMovies (ArrayList moviesInfo):
● Returns a list of movie names that both critics and the audience have rated above
85 (>= 85).
public ArrayList getCommonActors (String movie1, String movie2, ArrayList
actorsInfo)
● Given a pair of movies, this method returns a list of actors that acted in both
movies. You may think of how to use the 5 basic utility methods implemented
previously.
○ movie1 and movie2 are the names of movies as Strings
○ actorsInfo is the actor ArrayList
● In cases where the movies have no actors in common, it returns an empty list
● When writing test cases for this method, consider different kinds of user input. For
example:
○ Existing movies and non-existent movies. When movie1 or movie2 is
non-existent, there should be no actors in common.
Introduction to Software Development
○ Movie names should not be case sensitive, but spelling must be correct.
For example, “Rocky ii” and “Rocky II” should be considered the same
movie in the database.
○ Movie names with leading or trailing whitespace (e.g. “ Arrival “). For
example, “ Arrival “ and “Arrival“ should be considered the same movie
in the database.
○ movie1 and movie2 can be the same. In this case, return an ArrayList of
actor names that were cast in this movie.
public static double [] getMean (ArrayList moviesInfo)
● Given the moviesInfo DB, this static method returns the mean value of the critics ratings
and the audience ratings.
○ Returns the mean values as a double array, where the 1st item (index 0) is the
mean of all critics ratings and the 2nd item (index 1) is the mean of all audience
ratings
Testing
You have now seen how Test Driven Development works. For this homework, you are required
to write unit tests for each of the methods in MovieTrivia.java. While it might seem annoying at
first, I highly recommend doing this using a proper test-driven approach. First, write the unit
tests and then, implement the methods to pass your unit tests. Be thoughtful about writing a
good suite of tests to ensure proper behavior for the methods. Test typical inputs and edge
cases.
In the provided MovieTriviaTest.java file, we’ve created the test methods for you. We’ve also
created some of the test cases. (It does not have all the test cases the autograder will use).
We’ve also created a setUp method, which by default, is called before each and every test
method, and can be used to re-initialize objects. In our setUp method, we initialize the
MovieTrivia object to be used by each test method in the testing file.
Note, the Actor and Movie classes do not need to be tested. Also, the setUp, printAllActors,
and printAllMovies methods in the MovieTrivia class also do not need to be tested. Please do
not modify the code in these methods or in the Actor, Movie, or MovieDB classes.
Introduction to Software Development
You are expected to write additional test cases for each of the test methods given in the
MovieTriviaTest.java. Please make sure you have a total of at least 4 distinct, valid “test
case scenarios” for each test method.
Hint: when testing getMean, insert a new rating, then get mean again.
Note, a “test case scenario” can include multiple test cases that test a single scenario. For
example, see how we test the “insertActor” method below. First we initially call the
“insertActor” method. Then we have a test case that tests the new size of the actorsInfo
ArrayList, a test case that tests the name of the new actor in the actorsInfo ArrayList, a test
case that tests the size of the actor’s list of movies, and a test case that tests the name of one
of the actor’s movies. This is considered a complete “test case scenario”.
mt.insertActor("test123", new String [] {"testmovie1", "testmovie2"},
mt.actorsInfo);
assertEquals(mt.actorsInfo.size(), 4);
assertEquals(mt.actorsInfo.get(mt.actorsInfo.size() - 1).getName(),
"test123");
assertEquals(mt.actorsInfo.get(mt.actorsInfo.size() -
1).getMoviesCast().size(), 2);
assertEquals(mt.actorsInfo.get(mt.actorsInfo.size() -
1).getMoviesCast().get(0), "testmovie1");
You are not required to test helper methods that you write, but you are welcome to test them.
Comments & Style
Write comments using // for any non-trivial lines of code. In general, all of the style
conventions from Python also apply in Java. The main differences are in naming conventions
(lowercase and underscores versus camelCase) and the syntax for comments (/* */ versus ‘’’ ‘’’
and // versus #). The content of your comments should be very similar and the length of your
lines should not go off the right hand edge of the editing window.
Javadocs
If not already added, please add javadocs to all class definitions, methods, and instance
variables.
Introduction to Software Development
What to Submit
Please submit all the classes in your entire Java project. Make sure it includes everything in
your “src” folder, as well as any data files outside of the “src” folder. Do not remove the
package declarations in each file and keep the files in their respective package subdirectory.
Evaluation
1. Does your code function? Does it do what the specifications require?
(**AUTOGRADED**) (10 pts)
a. Did you implement the methods in the MovieTrivia class exactly as they have
been defined in this document?
b. We will run our own unit tests in addition to the ones provided and the ones you
write.
2. Did you have a total of at least 4 distinct, valid test case scenarios for each test
method? (10 pts)
a. Did you pass your own test cases?
b. Did you include general test case scenarios as well as edge cases?
3. Did you follow good programming practices? (7 pts)
a.
b. Did you reuse code to avoid repetition? When applicable, did you call some
methods inside other methods to cut down on code repetition? (+4)
c. Did you name additional variables and methods descriptively with camelCase?
(+1)
d. Did you add javadocs to classes, instance variables, and methods, and
comments to all non-trivial code? (+2)
4. Did you set up the files correctly? Does it compile and is everything named correctly? (3
pts)