Description
CircularSinglyLinkedList
You are to code a CircularSinglyLinkedList with head reference. A linked list is a collection of nodes,
each having a data item and references to other nodes. In a CircularSinglyLinkedList, each node has
references 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. As a special case, this means that in a one node list, the head node will point
to itself.
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 CircularSinglyLinkedList 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.
As an additional note, your circular implementation doesn’t have a tail reference, but it is still possible to efficiently add and remove from the head as well as add to the back in O(1) time. However, it
is still not possible to remove from the back in O(1) time unless the linked list is doubly-linked.
The examples below demonstrate what the CircularSinglyLinkedList should look like at various
states.
Size 0:
Size 1:
Size 4:
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Homework 2: CircularSinglyLinkedList Due: See Canvas
Nodes
The linked list consists of nodes. A class CircularSinglyLinkedListNode is provided to you. This class
has getter and setter methods to access and mutate the structure of the nodes.
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 specific index. See the javadocs for more details.
Removing
You will also implement three remove() methods – from the front, the back, or anywhere in the list given
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.
Garbage Collection
Java will automatically mark objects for garbage collection based on whether there is any means of
accessing the object. In other words, if we want to remove a node from the list, we must remove all
references to that node. What the next reference of that node points to doesn’t particularly matter.
As long as no references can reach the node, the node will be garbage collected eventually.
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).
Differences between Java API and This Assignment
Some of the methods in this assignment are called different things or don’t exist in Java’s LinkedList
class. Additionally, Java’s built in LinkedList is a Doubly-Linked List, so the efficiency of some operations will differ. This won’t matter until you tackle coding questions on the first exam, but it’s something
to be aware of. The list below shows all methods with a different name and their Java API equivalent if
it exists. The format is assignment method name ⇒ Java API name.
• addAtIndex(int index, T data) ⇒ add(int index, T data)
• addToFront(T data) ⇒ addFirst(T data)
• addToBack(T data) ⇒ add(T data) or addLast(T data)
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Homework 2: CircularSinglyLinkedList Due: See Canvas
• removeAtIndex(int index) ⇒ remove(int index)
• removeFromFront() ⇒ poll() or pollFirst()
• removeFromBack() ⇒ pollLast()
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Homework 2: CircularSinglyLinkedList Due: See Canvas
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
Efficiency 15pts
Total: 100pts
Provided
The following file(s) have been provided to you. There are several, but we’ve noted the ones to edit.
1. CircularSinglyLinkedList.java
This is the class in which you will implement the CircularSinglyLinkedList. Feel free to add
private helper methods but do not add any new public methods, inner/nested classes,
instance variables, or static variables.
2. CircularSinglyLinkedListNode.java
This class represents a single node in the linked list. It encapsulates the data and the next
reference. Do not alter this file.
3. CircularSinglyLinkedListStudentTest.java
This is the test class that contains a set of tests covering the basic operations on the CircularSinglyLinkedList
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 file(s). Make sure all file(s) listed below are in each submission, as
only the last submission will be graded. Make sure the filename(s) matches the filename(s) below, and
that only the following file(s) are present. The only exception is that Canvas will automatically append
a -n depending on the submission number to the file name(s). This is expected and will be handled by
the TAs when grading as long as the file name(s) before this add-on matches what is shown below. If
you resubmit, be sure only one copy of each file is present in the submission. If there are multiple files,
do not zip up the files before submitting; submit them all as separate files.
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Homework 2: CircularSinglyLinkedList Due: See Canvas
Once submitted, double check that it has uploaded properly on Canvas. To do this, download your
uploaded file(s) to a new folder, copy over the support file(s), recompile, and run. It is your sole responsibility to re-test your submission and discover editing oddities, upload issues, etc.
1. CircularSinglyLinkedList.java
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