Homework 2: Circular Singly-Linked List Solution






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 les that don’t compile. Any compile errors will result in a 0.


  1. Do not include any package declarations in your classes.


  1. Do not change any existing class headers, constructors, instance/global variables, or method sig-natures.


  1. Do not add additional public methods.


  1. 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.)


  1. Always be very conscious of e ciency. Even if your method is to be O(n), traversing the structure multiple times is considered ine cient unless that is absolutely required (and that case is extremely rare).


  1. You must submit your source code, the .java les, not the compiled .class


  1. After you submit your les, redownload them and run them to make sure they are what you intended to submit. You are responsible if you submit the wrong les.


Circular Singly-Linked List


You are to code a circular singly-linked list with a head reference. A linked list is a collection of nodes, each having a data item and a reference pointing to the next node. Since it must be circular, the next reference for the last node in this list will point to the head node. 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 setter and getter methods to access and mutate the structure of the nodes.




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, you will also be coding a method to remove the last instance of a piece of data. When removing from the front, the rst node should be removed in such a way that the last node points to the new front of the list (mind the e ciency!). When removing from the back, the last node should be removed and





Homework 2: Circular Singly-Linked List                                                  Due: See T-Square



have the new last node point to the head. When removing from the middle, the previous node of the removed node should point to the next node of the removed node. Make sure that you set any remaining pointers to the deleted nodes to null since in order for the node to be garbage collected, there cannot be any way to access the node. See the interface for more details.




There are two ways of de ning objects as equal: reference equality and value equality.


Reference equality is used when using the == operator. If two objects are equal by reference equal-ity, that means that they have the exact same memory locations. For example, say we have a Person object with a name and id eld. 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 de nition of equality is custom made for the object. For example, in that Person example above, we may want two objects to be con-sidered equal if they have the same name and id.


Keep in mind which makes more sense to use while you are coding.




Here is the grading breakdown for the assignment:


addAtIndex 10pts
addToFront 5pts
addToBack 5pts
removeAtIndex 10pts
removeFromFront 5pts
removeFromBack 5pts
removeLastOccurrence 10pts
get 10pts
toArray 6pts
clear 5pts
isEmpty 4pts
Checkstyle 10pts
E  ciency 15pts
Total: 100pts


Keep in mind that some functions are dependent on others to work, such as remove methods requiring the add methods to work. Also, the size function is used many times throughout the tests, so if the size isn’t updated correctly, many tests can fail.


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.







Homework 2: Circular Singly-Linked List                                                  Due: See T-Square



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 o a point for every style error that occurs. If you feel like what you wrote is in accordance with good style but still sets o the style checker please email Raymond Ortiz (rortiz9@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 mes-sage 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.”);





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.


break may only be used in switch-case statements


continue package


System.arraycopy() clone()




Arrays class Array class






Homework 2: Circular Singly-Linked List                                                  Due: See T-Square



Collections class




Re ection APIs


Inner or nested classes Lambda Expressions Method References


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.




The following   le(s) have been provided to you. There are several, but you will only edit one of them.


  1. java


This is the interface you will implement. All instructions for what the methods should do are in the javadocs. Do not alter this le.


  1. 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.


  1. java


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


  1. java


This is the test class that contains a set of tests covering the basic operations on the SinglyLinkedList 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 le(s). Failure to submit all required les may result in a 0 for the assignment. Please make sure the lename matches the lename(s) below. Be sure you receive the con rmation email from T-Square, and then download your uploaded les 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. java








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