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/**

* Singly Linked List

* Created by Devang on 03-Jan-17.

*/

public class MyDLinkedList<E> {

Node<E> header;

public MyDLinkedList() {

header = null;

}

public void addLast(E data) {

Node newNode = new Node(data);

if (header == null) {

header = newNode;

return;

}

Node currentNode = header;

while (currentNode.next != null) {

currentNode = currentNode.next;

}

currentNode.next = newNode;

newNode.previous = currentNode;

newNode.next = null;

}

public void addFirst(E data) {

Node newNode = new Node(data);

if (header == null) {

header = newNode;

newNode.next = null;

} else {

header.previous = newNode;

newNode.next = header;

header = newNode;

}

}

public void remove(E key) {

if (header == null) {

return;

}

if (header.data.equals(key)) {

header = header.next;

return;

}

Node currentNode = header;

while (!(currentNode.data.equals(key)) && !(currentNode.next == null)) {

if (currentNode.next.data.equals(key)) {

currentNode.next = currentNode.next.next;

return;

}

currentNode = currentNode.next;

}

}

public void insertAfter(E key, E data){

if (header == null) {

return;

}

Node newNode = new Node(data);

Node currentNode = header;

while (currentNode.next != null){

if(currentNode.data.equals(key)){

newNode.previous = currentNode;

newNode.next = currentNode.next;

currentNode.next = newNode;

currentNode.next.previous = newNode;

return;

}

currentNode = currentNode.next;

}

}

public void insertBefore(E key, E data){

if (header == null) {

return;

}

//If inserting before head

if(header.data.equals(key)){

addFirst(data);

return;

}

Node newNode = new Node(data);

Node currentNode = header;

//Else iterate till end

while (currentNode.next != null){

if(currentNode.data.equals(key)){

newNode.previous = currentNode.previous;

newNode.next = currentNode;

currentNode.previous = newNode;

return;

}

currentNode = currentNode.next;

}

}

public String toString() {

Node currentItem = header;

String output = "[";

int cnt = 0;

while (currentItem.next != null) {

if (cnt != 0)

output += ", ";

output += currentItem.data;

cnt++;

currentItem = currentItem.next;

}

if (cnt != 0)

output += ", ";

output += currentItem.data;

output += "]";

return output;

}

protected class Node<E> {

protected E data;

protected Node<E> previous;

protected Node<E> next;

protected Node(E data) {

this.data = data;

}

}

public static void main(String[] args) {

MyLinkedList list1 = new MyLinkedList();

list1.addLast("Hello");

list1.addLast("World");

list1.addLast("!");

System.out.println(list1);

list1.remove("!");

System.out.println(list1);

list1.addFirst("!");

System.out.println(list1);

list1.insertAfter("Hello", "Everyone");

System.out.println(list1);

list1.insertBefore("Hello", 125);

System.out.println(list1);

}

}