CS 1332 Homework 2: Doubly-Linked List




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Doubly-Linked List
You are to code a doubly-linked list with a head and tail reference. A linked list is a collection of nodes,
each having a data item and a reference pointing to the next node (and, in the case of this assignment,
a reference to the previous node). The next reference for the last node in this list and the previous
reference for the first node in this list would be 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 implement the LinkedListInterface provided. It will use the
default constructor (the one with no parameter) which is automatically provided by Java. Do not write
your own constructor.
The linked list consists of nodes. A class LinkedListNode is provided to you. LinkedListNode has five
methods to access and set the next node, access and set the previous node, and to access the data in the
You will implement three add() methods. One will add to the front, one will add to the back, and one
will add anywhere in the list. See the interface for more details.
Removing, just like adding, can be done from the front, the back, or anywhere in your linked list. In
addition, all instances of a specific value from the list can be removed. When removing from the front,
the first node should be removed and the head reference should be updated. When removing from the
Homework 2: Doubly-Linked List Due: See T-Square
back, the last node should be removed and the tail reference should be updated. When removing from
the middle, the previous node of the removed node should point to the next node of the removed node,
and the node following the removed node should point to the previous node of the removed node. Make
sure that you set any pointers to the deleted nodes to null. See the interface for more details.
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 T-Square under Resources, 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 in T-Square, under
Resources, 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 Carey MacDonald (careyjmac@gatech.edu) with the subject header of “CheckStyle XML”.
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.
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:
throw new PDFReadException(“Did not read PDF, will lose points.”);
throw new IllegalArgumentException(“Cannot insert null data into data structure.”);
If available, use the generic type of the class; do not use the raw type of the class. For example, use new
LinkedList() instead of new LinkedList(). Using the raw type of the class will result in a
Forbidden Statements
You may not use these in your code at any time in CS 1332.
• break may only be used in switch-case statements
Homework 2: Doubly-Linked List Due: See T-Square
• continue
• package
• System.arraycopy()
• clone()
• assert()
• Arrays class
• Array class
• Collections class
• Collection.toArray()
• Reflection APIs
• Inner or nested classes
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.
The following file(s) have been provided to you. There are several, but you will only edit one of them.
1. LinkedListInterface.java
This is the interface you will implement. All instructions for what the methods should do are in
the javadocs. Do not alter this file.
2. DoublyLinkedList.java
This is the class in which you will implement the interface. Feel free to add private helper methods
but do not add any new public methods, inner/nested classes, instance variables, or
static variables.
3. LinkedListNode.java
This class represents a single node in the linked list. It encapsulates data, the next reference, and
the previous reference. Do not alter this file.
4. 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.
You must submit all of the following file(s). Please make sure the filename matches the filename(s)
below. Be sure you receive the confirmation email from T-Square, and then download your uploaded
files to a new folder, copy over the interfaces, recompile, and run. It is your responsibility to re-test your
submission and discover editing oddities, upload issues, etc.
1. DoublyLinkedList.java