Description
You are to code a SinglyLinkedList with head and tail references. A linked list is a collection of
nodes, each having a data item and references to other nodes. In a SinglyLinkedList, each node has a
reference to the next node. Since it is non-circular, the next reference for the tail is 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 SinglyLinkedList 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 SinglyLinkedListNode 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).
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Homework 1: SinglyLinkedList Due: See Canvas
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)
• removeAtIndex(int index) ⇒ remove(int index)
• removeFromFront() ⇒ poll() or pollFirst()
• removeFromBack() ⇒ pollLast()
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Homework 1: SinglyLinkedList 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. SinglyLinkedList.java
This is the class in which you will implement the SinglyLinkedList. Feel free to add private
helper methods but do not add any new public methods, inner/nested classes, instance
variables, or static variables.
2. SinglyLinkedListNode.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. SinglyLinkedListStudentTest.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.
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. Do NOT submit SinglyLinkedListNode.java for this
homework; if you do, your homework will not compile on Gradescope. 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.
Once submitted, double check that it has uploaded properly on Gradescope. To do this, download
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Homework 1: SinglyLinkedList Due: See Canvas
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. SinglyLinkedList.java
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