Homework 2: Doubly-Linked Lists 

Homework 2: Doubly-Linked Lists 
Important
There are general homework guidelines you must always follow. If you fail to follow any of the following
guidelines you risk receiving a 0 for the entire assignment.
1. All submitted code must compile under JDK 8. This includes unused code, so don’t submit extra
files that don’t compile. Any compile errors will result in a 0.
2. Do not include any package declarations in your classes.
3. Do not change any existing class headers, constructors, instance/global variables, or method signatures.
4. Do not add additional public methods.
5. Do not use anything that would trivialize the assignment. (e.g. don’t import/use java.util.ArrayList
for an Array List assignment. Ask if you are unsure.)
6. Always be very conscious of efficiency. Even if your method is to be O(n), traversing the structure
multiple times is considered inefficient unless that is absolutely required (and that case is extremely
rare).
7. You must submit your source code, the .java files, not the compiled .class files.
8. After you submit your files, redownload them and run them to make sure they are what you
intended to submit. You are responsible if you submit the wrong files.
Doubly-Linked List
You are to code a non-circular doubly-linked list with head and tail references. A linked list is a collection
of nodes, each having a data item and references to the previous and next nodes. The previous reference
for the head/first node will point to null. The next reference for the tail/last node in this list will point
to null. Do not use a phantom node to represent the start or end of your list. A phantom or sentinel
node is a node that does not store data held by the list and is used solely to indicate the start or end of
a linked list. If your list contains n elements, then it should contain exactly n nodes.
Your linked list implementation will use the default constructor (the one with no parameter) which is
automatically provided by Java. Do not write your own constructor. Specifications for efficiency and
what the method should do are provided in the javadocs.
Nodes
The linked list consists of nodes. A class LinkedListNode is provided to you. LinkedListNode has
setter and getter methods to access and mutate the structure of the nodes.
Traversing
When the LinkedList is doubly-linked like in this assignment, you are able to traverse the list from both
ends depending on which makes more sense. For example, if you know the index you want is close to the
end of the list, you’d start traversing from the tail and go backwards; the opposite applies if the index
is close to the beginning of the list. You should make this optimization wherever it applies.
Adding
You will implement three add() methods. One will add to the front, one will add to the back, and one
will add at a specific index. See the javadocs for more details.
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Homework 2: Doubly-Linked Lists Due: See Canvas
Removing
Removing, just like adding, can be done from the front, the back, or from a specific index. Make sure
that there is no longer any way to access the removed node so that the node will be garbage collected.
See the javadocs for more details.
Equality
There are two ways of defining objects as equal: reference equality and value equality.
Reference equality is used when using the == operator. If two objects are equal by reference equality, that means that they have the exact same memory locations. For example, say we have a Person
object with a name and id field. If you’re using reference equality, two Person objects won’t be considered
equal unless they have the exact same memory location (are the exact same object), even if they have
the same name and id.
Value equality is used when using the .equals() method. Here, the definition of equality is custom
made for the object. For example, in that Person example above, we may want two objects to be considered equal if they have the same name and id.
Keep in mind which makes more sense to use while you are coding. You will want to use value
equality in most cases in this course when comparing objects. Notable cases where you’d
use reference equality include checking for null or comparing primitives (in this case, it’s
just the == operator being overloaded).
Grading
Here is the grading breakdown for the assignment. There are various deductions not listed that are
incurred when breaking the rules listed in this PDF, and in other various circumstances.
Methods:
addAtIndex 10pts
addToFront 5pts
addToBack 5pts
removeAtIndex 10pts
removeFromFront 5pts
removeFromBack 7pts
lastOccurrence 8pts
get 10pts
toArray 6pts
clear 5pts
isEmpty 4pts
Other:
Checkstyle 10pts
Efficiency 15pts
Total: 100pts
Keep in mind that add functions are necessary to test other functions, so if an add doesn’t work, remove
tests might fail as the items to be removed were not added correctly. Additionally, the size function is
used many times throughout the tests, so if the size isn’t updated correctly or the method itself doesn’t
work, many tests can fail.
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Homework 2: Doubly-Linked Lists Due: See Canvas
A note on JUnits
We have provided a very basic set of tests for your code, in LinkedListStudentTests.java. These
tests do not guarantee the correctness of your code (by any measure), nor does it guarantee you any
grade. You may additionally post your own set of tests for others to use on the Georgia Tech GitHub as
a gist. Do NOT post your tests on the public GitHub. There will be a link to the Georgia Tech GitHub
as well as a list of JUnits other students have posted on the class Piazza.
If you need help on running JUnits, there is a guide, available on Canvas under Files, to help you
run JUnits on the command line or in IntelliJ.
Style and Formatting
It is important that your code is not only functional but is also written clearly and with good style. We
will be checking your code against a style checker that we are providing. It is located on Canvas, under
Files, along with instructions on how to use it. We will take off a point for every style error that occurs.
If you feel like what you wrote is in accordance with good style but still sets off the style checker please
email Tim Aveni (tja@gatech.edu) with the subject header of “[CS 1332] CheckStyle XML”.
Javadocs
Javadoc any helper methods you create in a style similar to the existing Javadocs. If a method is
overridden or implemented from a superclass or an interface, you may use @Override instead of writing
Javadocs. Any Javadocs you write must be useful and describe the contract, parameters, and return
value of the method; random or useless javadocs added only to appease Checkstyle will lose points.
Vulgar/Obscene Language
Any submission that contains profanity, vulgar, or obscene language will receive an automatic zero on
the assignment. This policy applies not only to comments/javadocs but also things like variable names.
Exceptions
When throwing exceptions, you must include a message by passing in a String as a parameter. The message must be useful and tell the user what went wrong. “Error”, “BAD THING HAPPENED”,
and “fail” are not good messages. The name of the exception itself is not a good message.
For example:
Bad: throw new IndexOutOfBoundsException("Index is out of bounds.");
Good: throw new IllegalArgumentException("Cannot insert null data into data structure.");
Generics
If available, use the generic type of the class; do not use the raw type of the class. For example, use new
LinkedList<Integer() instead of new LinkedList(). Using the raw type of the class will result in a
penalty.
Forbidden Statements
You may not use these in your code at any time in CS 1332.
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Homework 2: Doubly-Linked Lists Due: See Canvas
• package
• System.arraycopy()
• clone()
• assert()
• Arrays class
• Array class
• Thread class
• Collections class
• Collection.toArray()
• Reflection APIs
• Inner or nested classes
• Lambda Expressions
• Method References (using the :: operator to obtain a reference to a method)
If you’re not sure on whether you can use something, and it’s not mentioned here or anywhere else in
the homework files, just ask.
Debug print statements are fine, but nothing should be printed when we run your code. We expect
clean runs - printing to the console when we’re grading will result in a penalty. If you submit these, we
will take off points.
Provided
The following file(s) have been provided to you. There are several, but we’ve noted the ones to edit.
1. DoublyLinkedList.java
This is the class in which you will implement the methods. Feel free to add private helper methods
but do not add any new public methods, inner/nested classes, instance variables, or
static variables.
2. LinkedListNode.java
This class represents a single node in the linked list. It encapsulates the data, the previous, and
the next reference. Do not alter this file.
3. LinkedListStudentTests.java
This is the test class that contains a set of tests covering the basic operations on the DoublyLinkedList
class. It is not intended to be exhaustive and does not guarantee any type of grade. Write your
own tests to ensure you cover all edge cases.
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Homework 2: Doubly-Linked Lists Due: See Canvas
Deliverables
You must submit all of the following file(s). Please make sure the filename matches the filename(s)
below, and that only the following file(s) are present. If you make resubmit, make sure only one copy of
the file is present in the submission.
After submitting, double check to make sure it has been submitted on Canvas and then download your
uploaded files to a new folder, copy over the support files, recompile, and run. It is your responsibility
to re-test your submission and discover editing oddities, upload issues, etc.
1. DoublyLinkedList.java
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