Homework 2: DoublyLinkedList Solution

DoublyLinkedList




You are to code a non-circular DoublyLinkedList with head and tail references. A linked list is a col-lection of nodes, each having a data item and references to other nodes. In a DoublyLinkedList, each node has references to the previous and next nodes. The previous reference for the head/ rst node will point to null. The next reference for the tail/last node 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.




The DoublyLinkedList must follow the requirements stated in the javadocs of each method you must implement. Your linked list implementation will use the default constructor (the one with no parameters) which is automatically provided by Java. Do not write your own constructor.




Nodes




The linked list consists of nodes. A class DoublyLinkedListNode is provided to you. DoublyLinkedListNode has getter and setter methods to access and mutate the structure of the nodes.




Traversing




You are able to traverse a DoublyLinkedList 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 to anywhere in the list given a speci c index. See the javadocs for more details.







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Homework 2: DoublyLinkedList Due: See Canvas










Removing




You will also implement three remove() methods - from the front, the back, or anywhere in the list given a speci c 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.




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
5pts




get
10pts




isEmpty
4pts




clear
5pts




removeLastOccurrence
10pts




toArray
6pts




Other:






Checkstyle
10pts




E ciency
15pts




Total:
100pts







JUnits




We have provided a very basic set of tests for your code. These tests do not guarantee the correctness of your code (by any measure), nor do they 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.




Collaboration Policy




Every student is expected to read, understand and abide by the Georgia Tech Academic Honor Code.




When working on homework assignments, you may not directly copy code from any source (other than your own past submissions). You are welcome to collaborate with peers and consult external re-sources, but you must personally write all of the code you submit. You must list, at the top of each le in your submission, every student with whom you collaborated and every resource you consulted while completing the assignment.




You may not directly share any les containing assignment code with other students or post your code publicly online. If you wish to store your code online in a personal private repository, you can use Github Enterprise to do this for free.










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Homework 2: DoublyLinkedList Due: See Canvas










The only code you may share is JUnit test code on a pinned post on the o cial course Piazza. Use JUnits from other students at your own risk; we do not endorse them. See each assignment’s PDF for more details. If you share JUnits, they must be shared on the site speci ed in the Piazza post, and not anywhere else (including a personal GitHub account).




Violators of the collaboration policy for this course will be turned into the O ce of Student Integrity.




Style and Formatting




It is important that your code is not only functional, but written clearly and with good programming style. Your code will be checked against a style checker. The style checker is provided to you, and is located on Canvas. It can be found under Files, along with instructions on how to use it. A point is deducted for every style error that occurs. If there is a discrepancy between what you wrote in accordance with good style and the style checker, then address your concerns with the Head TA.




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 HAP-PENED", 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.




package




System.arraycopy() clone()




assert()




Arrays class







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Homework 2: DoublyLinkedList Due: See Canvas










Array class Thread class




Collections class




Collection.toArray()




Re ection 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 les, just ask.




Debug print statements are ne, 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 o points.




Provided




The following le(s) have been provided to you. There are several, but we’ve noted the ones to edit.




DoublyLinkedList.java



This is the class in which you will implement the DoublyLinkedList. Feel free to add private helper methods but do not add any new public methods, inner/nested classes, instance variables, or static variables.




DoublyLinkedListNode.java



This class represents a single node in the linked list. It encapsulates the data, and the previous and next references. Do not alter this le.




DoublyLinkedListStudentTest.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.




Deliverables




You must submit all of the following le(s). Please make sure the lename(s) matches the lename(s) below, and that only the following le(s) are present. The only exception is that Canvas will automat-ically append a -n depending on the submission number to the le name. This is expected and will be handled by the TAs when grading as long as the le name before this add-on matches what is shown below. If you resubmit, be sure only one copy of the le is present in the submission. If there are multiple les, do not zip up the les before submitting; submit them all as separate les.




Once submitted, double check that it has uploaded properly on Canvas. To do this, download your uploaded les to a new folder, copy over the support les, recompile, and run. It is your sole responsi-bility to re-test your submission and discover editing oddities, upload issues, etc.







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Homework 2: DoublyLinkedList Due: See Canvas










DoublyLinkedList.java



































































































































































































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