Description
Introduction
The goal of this assignment is to practice thinking about designing software using object-oriented
programming techniques in Java. Somewhat similar to our discussion during class of match.com, the theme
of this programming project will also be social networks. In particular, this project asks you to think about
how you would build a site called Facebuk, described in the next section.
Facebuk
People, Pets, & Possessions
Facebuk is a social networking site, somewhat akin to Facebook, that supports profiles not only for people, but also people’s pets and possessions. People love their pets and love posting photos of their pets. Moreover,
people sometimes want to sell their possessions online. As an example of how Facebuk might look, suppose
that Melania Trump decided to join Facebuk:
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Melania’s Facebuk page above shows that:
Her friends consist of Ivana Trump (the ex-wife of Melania’s current husband), Kevin Hart, Hillary
Clinton, and Marlon Bundo (a bunny that belongs to a different family).
Melania has one (somewhat reclusive) pet: a goldfish named Humphrey.
Melania also owns some silver jewelry as a possession. Melania has, at certain moments (defined in the next section), appeared in photographs both with her
daughter (Ivanka, not to be confused with Ivana) as well as a Saudi prince.
Below is the Facebuk page of Melania’s silver jewelry (on sale):
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Marlon Bundo is the pet bunny of Karen Pence. (Karen’s husband is the Vice President of a largish country in
North America.) Marlon has his own Facebuk page too, which shows that he has four friends of his own:
Charlotte Pence (the daughter of Karen Pence), Melania Trump, Humphrey, and Kevin Hart.
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Friend Requests
Over the course of life, sometimes people (and pets) make new friends. In order to make this relationship
official on Facebuk, a FriendRequest needs to be created, and then it must be approved by both friends. The
FriendRequest stores both A and B, as well as whether A and/or B has approved the request. Once both
parties have approved the request (but not before), then A is added to B’s list of friends, and B is also added
to A’s list of friends. (Facebuk requires that both friends approve it because Facebuk itself might suggest two
people to become friends.)
Moments
In addition to linking people, pets, and possessions, Facebuk also enables users to capture moments in which
multiple people and pets — but not possessions — participated and are captured in a photograph. (Note that
just because two participants are both in the same moment does not imply that they are friends.) See one of
the Pence family’s moments below, in which a list of the participants is displayed below the photo:
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Happiness
Facebuk wants its users to be happy (isn’t that nice?). For this reason, Facebuk provides its users with the
ability to tag each moment with how happy each participant — which can be either a person or a pet —
appears during that moment’s image. These “happiness” tags could be provided by some sort of automatic
happiness or smile detector (as we will discussed in class). However, in this project, for simplicity, they will
just be input manually.
Using this “happiness” information, Facebuk can offer its users two special search functions:
For a specific person p, find the friend f — who can be either a Person or a Pet — with whom person p
appears the most happy on average, over all the moments in which both p and her/his friend f
participate. If person p has no friends with whom she/he appears in the same moment, then return null. 1.
For a specific person p, find the moment m (in which p participated) in which the average happiness
value — over all participants in m (including both people and pets) — is highest. If the person does not
participate in any moments, then return null. 2.
By “average” we mean the arithmetic mean. Going Out with Friends
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Sometimes it’s nice to hang out with friends…especially when everybody in the group is friends with
everybody else. What is the largest set of friends you can go to the movies with such that everybody in the
set is friends with everybody else? In computer science and graph theory, this kind of set is called a
maximum clique (which is different from a maximal clique). It isn’t always easy to determine, but
fortunately Facebuk offers a “Maximum Clique Finder” service that gives you the answer. As an example,
suppose:
Melania’s friends are: Ivana Trump, Kevin Hart, Hillary Trump, and Marlon Bundo.
Marlon’s friends are: Melania Trump, Charlotte Pence, Kevin Hart, and Humphrey.
Ivana’s friends are: Melania Trump, Tom Cruise, Hillary Clinton, and Kevin Hart.
Kevin’s friends are: Melania Trump, Marlon Bundo, Robin Wright, Hillary Clinton, Humphrey, and
Ivana Trump.
Hillary’s friends are: Melania Trump, Ivana Trump, Kevin Hart, and Robin Wright.
In this case, the largest set — i.e., the maximum clique — of friends with whom Melania could go out is:
Ivana, Kevin, and Hillary. Marlon cannot go because he is not friends with Hillary or Ivana :-(.
Requirements
This project consists of both data modeling and algorithmic challenges:
R1: Data modeling
Your job is to implement a set of classes to support the fundamental objects that constitute Facebuk, as well
as the relationships that connect the different objects together. In particular, you must support the creation of
objects of type:
Person: Each person can have pets, friends (both people and pets), and possessions. Also, she/he can
participate in moments.
Pet: Each pet has a sole (i.e., just one) owner (who must be a person) and can have friends (both
people and pets).
Possession: Each possesion has a sole owner (who must be a person), and it has a price; it has no
friends :-(.
Moment: Each moment is associated with a list of participants along with their respective happiness
values.
In addition, all objects have a name and an image. To keep things simple, we pretend to “load” an Image from
disk by specifying a hypothetical filename, e.g., new Image(“Barack.png”). No matter how you design your set of classes, you are required to include the following constructors:
Person (String name, Image image)
Pet (String name, Image image)
Possession (String name, Image image, float price)
Moment (String name, Image image, ArrayList participants, ArrayList smileValues), in
which the array of participants should contain objects of either type Person or Pet, and the array
smileValues should contain objects of type Float that correspond to the levels of happiness of each
person/pet.
In addition, implement the following methods, which should be callable on objects of type Person or Pet:
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void setFriends (ArrayList friends) — sets the list of friends for the target person/pet
void setMoments (ArrayList moments) — sets the list of moments for the target person/pet
ArrayList getFriends () — returns an ArrayList of the person’s/pet’s friends
void addFriend (… friend) — adds a new friend to the list of friends of the target object. (Note
that … is not real Java code — you will need to change this to whatever type is appropriate given your
implementation. Also, for simplicity, you do not need to check whether the specified friend was already
a friend of the target object.)
The FriendRequest class should have the following methods:
FriendRequest (… entity1, … entity2) — constructor that specifies the two “entities” (person
or pet) of the friend request.
void approve (… entity) — called when the specified entity approves the request; once both
entities of the request have approved it, then entity1 and entity2 should be added to their respective lists
of friends. If the specified entity was not one of the two entities specified during construction, then this
method should throw an IllegalArgumentException. For Person but not Pet, implement:
void setPossessions (ArrayList possessions) — sets the list of possessions for the target person
void setPets (ArrayList pets) — sets the list of pets for the target person
For Possession and Pet, implement:
void setOwner (Person owner) — sets the sole owner for the target possession/pet
For Possession, implement:
float getPrice () — returns the price of the possession
Finally, you should implement an equals method that is callable on objects of all four main classes (Person, Pet, Possession, and Moment):
boolean equals (Object o) — returns true if and only if the name of the target object is equal to the
name of the specified object o. In addition to writing Java code that models the objects and relationships described above, you also need to
describe your rationale for how and why you created the classes that you chose. In particular, in a README
file, for every class (abstract or concrete) that you use, describe why you use it and what purpose it serves
within the greater project. Since Person, Possession, Pet, and Moment are all required, you do not need to
justify their existence.
Design goals
The goal of this part of the assignment is to use classes (concrete or abstract) so as to (1) minimize code
redundancy between different components (people, pets, etc.) of the project. At the same time, you need to
(2) make sure that every class represents a coherent and meaningful entity — it should not just be a “grabbag” of methods. Both (1) and (2) are tenets of good object-oriented design.
ArrayList
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length list — similar in purpose to an array, but you don’t have to resize it every time the array reaches
capacity. ArrayList is an extremely useful class in many applications, and we will talk about several other
useful data structures over the coming 1-2 weeks.
The proper way of using an ArrayList is to specify the type of object you want to store in it when you
declare and instantiate it. However, this gets surprisingly complicated when you want to store objects that
can derive from a hierarchy of classes and/or implement one or more interfaces (which we will discuss in
class soon). We will cover this later in this course. For now, you should use ArrayList in a “type-unsafe”
fashion: just declare, instantiate, and use it in the following way:
ArrayList list = new ArrayList();
list.add(person);
where person is an object of type Person. Because this is “type-unsafe”, you will get a compiler warning:
make Note: FacebukTester.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
It’s ok to ignore this warning for this assignment.
To later retrieve an object from the array, use: list.get(idx); where idx is the index of the element you
want to retrieve. Note that, when you use ArrayList in this manner, the return value of list.get(idx) will
be an Object; hence, to cast it back to a Person, use: Person p = (Person) list.get(idx); The cast will
become unnecessary once we talk about generic types later in the course.
R2: Happiness computation
Your code should implement the following methods that can be called on objects of type Person or Pet:
getFriendWithWhomIAmHappiest () which returns either a Pet or a Person (hence, you will need to
choose the return type to be sufficiently flexible)
getOverallHappiestMoment () which returns Moment
For a description of what these should do, see above section on happiness. We will test your code
automatically and/or by manual inspection.
R3: Finding a Maximum Clique of Friends
Implement the following methods, both which can be called on objects of type Person or Pet:
ArrayList findMaximumCliqueOfFriends () — return a list containing a maximum clique of friends
with whom the target person/pet could go out, such that each of his/her friends is also friends with
everyone else in the set.
static boolean isClique (ArrayList set) — returns true if and only if all the people/pets in the
specified set are all friends with each other. (Note: if set is empty, then this method should return true
since there is no one in the set who is not friends with another member of the set.) Since this is a helper
method that should not depend on any instance variables of the target object, it can (and should) be
declared static. Even though this is a helper method, make sure it is declared public so we can test
it!
Details:
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The set can contain both people and pets.
The set should not contain the target person/pet on which the method was called.
If there are multiple such “largest sets” (aka maximum cliques) for the target person/pet, then it’s fine to
return any of them.
The set of friends can be stored in the ArrayList in any order.
Teamwork
You may work as a team (2 people) on this project.
Getting started
Download this zip file that contains FacebukTester.java and Image.java. You should not need to modify
the Image class, but you likely will want to add more tests to the tester.
Next, make sure you have downloaded and installed JUnit. In CS 2103, we will use version 4.12. There are
two Jar files you need to download:
junit-4.12.jar
hamcrest-core-1.3.jar
See here for more information.
On the data modeling part of the project, consider what pets and people have in common, and then consider
how they differ. “Factor out” the common functionality into a common (abstract) superclass (e.g.,
LivingEntity that can represent both pets and people).
Unit testing
We have given you starter code (FacebukTester.java) to help you with testing. We will use a larger version
of this file to test your code; hence, it is absolutely imperative that your code can compile against this
tester. If your code does not compile against our test code, you may unfortunately get 0 credit.
Grading
Grading will be based on (1) your code compiling against our test code; (2) your written description (in the
README you write) and justification of the design choices you made; (3) your code passing our test cases; and
(4) your adherence to consistent and appropriate style. In particular, make sure your code adheres to the style
guidelines given during the first week of class. You additionally need to make sure that your use of
whitespace is consistent — no randomly ragged indentation is permitted.
In order to receive full-credit on the data modeling portion of this project, you need to make sure that you
have used classes (concrete or abstract) so that (1) they represent coherent, meaningful objects in the Facebuk
ecosystem you are modeling, and (2) so as to minimize code redundancy.
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What to Submit
Create a Zip file containing all of your .java files (no class files), as well as a README file describing your
object-oriented design rationale. (Important note: The file must be a Zip file, not a gz, rar, or 7z file!)
Submit the Zip file you created to InstructAssist. Submission deadline: Tuesday, October 30, at 11:59pm
EDT.
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