public class LinkedList $\{$

private Node head;

private Node tail;

$//$ About method

public String About$()\{$

return "This LinkedList class was implemented by Gabriel";

$\}$

$//$ AddHead method

public void AddHead$($String value$)\{$

Node newNode $=$ new Node$($value$)$;

newNode.next $=$ head;

head $=$ newNode;

if $($tail $==$ null$)\{$

tail $=$ head;

$\}$

$\}$

$//$ AddTail method

public void AddTail$($String value$)\{$

Node newNode $=$ new Node$($value$)$;

if $($tail $==$ null$)\{$

head $=$ tail $=$ newNode;

$\}$ else $\{$

tail.next $=$ newNode;

tail $=$ newNode;

$\}$

$\}$

$//$ RemoveHead method

public String RemoveHead$()\{$

if $($head $==$ null$)\{$

return $""$;

$\}$

String value $=$ head.value;

head $=$ head.next;

if $($head $==$ null$)\{$

tail $=$ null;

$\}$

return value;

$\}$

$//$ RemoveTail method

public String RemoveTail$()\{$

if $($head $==$ null$)\{$

return $""$;

$\}$

if $($head $==$ tail$)\{$

String value $=$ head.value;

head $=$ tail $=$ null;

return value;

$\}$

Node current $=$ head;

while $($current$.$next $!=$ tail$)\{$

current $=$ current.next;

$\}$

String value $=$ tail.value;

tail $=$ current;

tail.next $=$ null;

return value;

$\}$

$//$ IsEmpty method

public boolean IsEmpty$()\{$

return head $==$ null;

$\}$

$//$ ToString method

public String ToString$()\{$

if $($head $==$ null$)\{$

return $""$;

$\}$

StringBuilder sb $=$ new StringBuilder$()$;

Node current $=$ head;

while $($current $!=$ null$)\{$

sb$.$append$($current$.$value$)$;

if $($current$.$next $!=$ null$)\{$

sb$.$append$(",")$;

$\}$

current $=$ current.next;

$\}$

return sb$.$toString$()$;

$\}$

$//$ ToStringReverse method

public String ToStringReverse$()\{$

if $($head $==$ null$)\{$

return $""$;

$\}$

StringBuilder sb $=$ new StringBuilder$()$;

Node current $=$ tail;

while $($current $!=$ null$)\{$

sb$.$append$($current$.$value$)$;

if $($current $!=$ head$)\{$

sb$.$append$(",")$;

$\}$

current $=$ current.prev;

$\}$

return sb$.$toString$()$;

$\}$

$//$ Node class

private class Node $\{$

private String value;

private Node next;

private Node prev; $//$ for ToStringReverse

public Node$($String value$)\{$

this.value $=$ value;

$\}$

$\}$

$\}$

In java programming, can you add a code in main class on how to read a file under LinkedList programming, and please do not put it inside the LinkedList class. Part $3$: Testing

A number of test files will be provided to you for testing your code. The format is designed to be easy to read in multiple

programming languages. You need to use the classes, built in your programming language, to read the source files.

File Format

The first line of the data contains the total digits in the key. You might want to save this value $-$ I can be used to separate the

key from the value $($using the substring function found in most programming languages$).$

Value $1$

Value $2$

$...$

Value $n$

END

The following is one of the most basic test files on the website.

File: years.txt

Sutter's Fort $(1839)$

Bear Flag Revolt $(1846)$

Sacramento state $(1947)$

Nachos $(1953)$

Buffalo wings $(1964)$

Great Toilet Paper Shortage $(2020)$

END

Reading the File

Different programming languages implement file IO in different ways. Some use classes and others use more primitive $($or

ingrained$)$ features. This will take the form of either a While Loop or a Do Loop. In all cases, your main testing class will read

the contents of the file and it to a instance of your linked$-$list class.

Do not make this a method in your LinkedList $-$ keep it in main$().$ Why? It will make future assignments easier.

In the pseudocode below, I show the basic approach for both types of loops. Your programming language will use one or the

other. Some programming languages will return Null if the end of the file was reached. Others may contain a method on the

file reading class.

while the file has more data

read a value

list.AddTail $($value$)$

end while

print list. Tostring $()$

print list. ToStringReverse $()$