Hello, guys! I hope you'd able to help me with this question in java about doubly linked list.

I am trouble with method1: deleteLetter(char c), method 2: removeFirstLast(), method 3: makePallindrome. method4: lettetPresent(char l)

Method 1

public void deleteLetter(char c){

//your code here

}

This method deletes all instances of the letter provided as the parameter from the doubly lined list. For example: myList.delete(n), all n characters will be deleted from the doubly linked list. In the example below, annex to would be reduced to aex. See Figure 1.

Figure1

Method 2

public void removeFirstLast(){

//your code here

}

This method removes the character(s) that are at the head and tail of the doubly linked list. For example: myList.removeFirstLast(), on a doubly linked list containing annex would reduce it to nne. See Figure2.

Figure2

Method 3

public void makePallindrome(){

//your code here

}

This method takes the existing letters in the doubly linked list and makes it a palindrome (using the tail as the pivot for the mirror image). For example: myList.makePallindrome(), on a doubly linked list containing aex would result in a doubly linked list that contains aexea. See Figure3.

Figure3

Method 4

public boolean letterPresent(char l){

//your code here

}

This method returns true if the char in the method parameter is present in the doubly linked list and false if it is not present. For example: myList.letterPresent(a) and myList.letterPresent(z) will return true and false respectively if called on a double linked list containing annex.

import java.util.*;

class Node

{

private char letter;

private Node next, prev;

public Node(char c)

{

letter = c;

next = prev = null;

}

public char getLetter()

{

return letter;

}

public Node getNext()

{

return next;

}

public void setNext(Node n)

{

next = n;

}

public Node getPrev()

{

return prev;

}

public void setPrev(Node p)

{

prev = p;

}

}

public class L1Example

{

Node head, tail;

public L1Example()

{

head = tail = null;

}

public boolean isPalindrome()

{

//your code here

return false;

}

////////////////////////////////////////////////////////////////////////////////////

public void deleteLetter(char c)

{

}

public void removeFirstLast()

{

//this method deletes the first node

if (head == null)

{

return;

}

if (head.getNext() == null)

{

head = null;

return;

}

head = head.getNext();

head.prev() = null;

//this is a reference

Node c = head;

// this method deletes the last node.

while (c.getNext() != null)

c = c.getNext();

c.prev.next() = null;

}

public void makePallindrome()

{

}

/*public boolean letterPresent(char l)

{

}*/

////////////////////////////////////////////////////////////////////////////////////

public String concatinateBackward()

{

Node curr = tail;

String backward=" ";

while(curr!=null)

{

backward = backward+curr.getLetter();

curr = curr.getPrev();

}

return backward;

}

public void firstBecomesLast()

{

}

public void insert(char c)

{

Node nd = new Node(c);

nd.setNext(head);

if(head != null)

head.setPrev(nd);

else

tail = nd;

head = nd;

}

public void insert2(char c)

{

}

public static void main(String[] args)

{

L1Example myList = new L1Example();

myList.insert('a');

myList.insert('b');

myList.insert('c');

myList.insert('c');

myList.insert('d');

myList.insert('e');

System.out.println("The list read from tail to head:" +myList.concatinateBackward());

}

}