class DllNode{

private int data;

private DllNode prev;

private DllNode next;

public DllNode(int data){

this.data = data;

prev = null;

next = null;

}

public DllNode(int data , DllNode prev,DllNode next){

this.data = data;

this.prev = prev;

this.next = next;

}

public int getData(){

return data;

}

public DllNode getNext(){

return next;

}

public DllNode getPrev(){

return prev;

}

public void setPrev(DllNode node){

prev = node;

}

public void setNext(DllNode node){

next = node;

}

}

public class DoublyLinkedList{

private DllNode head;

private DllNode tail;

private int length;

public DoublyLinkedList(){

head = new DllNode(Integer.MIN_VALUE,null,null);

tail = new DllNode(Integer.MIN_VALUE,head,null);

head.setNext(tail);

length = 0;

}

public int getPosition(int data){

DllNode temp = head;

int pos = 0;

while(temp != null){

if(temp.getData() == data){

return pos;

}

pos+=1;

temp = temp.getNext();

}

return Integer.MIN_VALUE;

}

public int getLength(){

return length;

}

public void insertAtHead(int value){

DllNode node = new DllNode(value,null,null);

if(length == 0){

head.setNext(node);

node.setPrev(head);

tail.setPrev(node);

node.setNext(tail);

length += 1;

return;

}

else{

node.setNext(head.getNext());

node.setPrev(head);

head.setNext(node);

length += 1;

}

}

public void insertAt(int data , int position){

if(position < 0){

position = 0;

}

if(position > length){

position = length;

}

DllNode node , temp = head;

if(head == null){

head = new DllNode(data);

tail.setPrev(head);

head.setNext(tail);

}

//when want to insert at head

if(position == 0){

insertAtHead(data);

}

else if(position == length){

insertAtTail(data);

}

else{

for(int i = 1 ; i <= position ; i++){

temp = temp.getNext();

}

//we have reached a position before now.

node = new DllNode(data,null,null);

node.setNext(temp.getNext());

node.setPrev(temp);

temp.getNext().setPrev(node);

temp.setNext(node);

length += 1;

}

}

public void insertAtTail(int data){

DllNode node = new DllNode(data,null,null);

if(length == 0){

insertAtHead(data);

return;

}else{

tail.getPrev().setNext(node);

node.setPrev(tail.getPrev());

tail.setPrev(node);

length += 1;

}

}

public int removeFirst(){return 0;}

public int removeLast(){return 0;}

public synchronized void removeMatched(DllNode node){}

public String toString(){

String result = "[";

DllNode node = head.getNext();

for(int i = 0 ; i < length ; i++){

result += node.getData();

if( i != (length - 1)){

result += ",";

}

node = node.getNext();

}

result += "]";

return result;

}

public static void main(String[] args){

DoublyLinkedList dll = new DoublyLinkedList();

dll.insertAtHead(5);

System.out.println(dll.toString());

System.out.println("list Length " + dll.getLength());

dll.insertAtHead(15);

System.out.println(dll.toString());

System.out.println("list Length " + dll.getLength());

dll.insertAtTail(25);

System.out.println(dll.toString());

dll.insertAt(35,1);

System.out.println(dll.toString());

dll.insertAt(45,dll.getLength());

System.out.println(dll.toString());

dll.insertAt(65,dll.getLength() - 1);

System.out.println(dll.toString());

}

}