public class DoublyLinkedList {

	private Node head;
	private Node tail;
	private int count;


	 public void addHead(Object x){
		 if(count==0)
			head = tail=new Node(x);
		 else
		 {
			Node current = new Node(x);
			current.next = head;
			head=current;
		 }
		 count++;
	}
	 public void addTail(Object x){
		 if(count==0)
			 addHead(x);
			 else{
				Node current = new Node(x);
			 tail.next = current;
			 tail=current;
			 }
			 count++;
	 }

	public Node getHead() {
		 if(count==0)
			 return null;
		 else
			 return head;
	}


	public Node getTail() {
		 if(count==0)
			 return null;
		 else
			 return tail;
	}

	 public void printList(){
		 if(count==0)
			System.out.println("the list is empty");
		 else{
			 Node current;
			 current=head;
			 while(current!=null){
				 System.out.println(current.data);
				 current=current.next;
			 }

		 }
	 }

		public void insertAtPos(int at, Object data) {
			if (at == 0) {
				insertAtHead(data);
				return;
			} else if (at > length() ) {
				System.out.println("Error position out of range");
				return;
			} else if (at == length() ) {
				insertAtTail(data);
				return;
			} else {
				int points = 0;
				Node current = head;
				while(current != null && points < at){
					current = current.getNext();
					points++;
				}
				Node node = new Node(data);
				node.setPrev(current);
				node.setNext(current.getNext());
				current.setNext(node);
				current.getNext().setPrev(node);
			}
		}



		public void insertAtHead(Object data) {
			Node node = new Node(data);
			if (head == null) {
				head = node;
				tail = node;
				return;
			} else {
				node.setNext(head);
				head.setPrev(node);
				head = node;
			}
		}

		public void insertAtTail(Object data) {
			Node node = new Node(data);
			if (head == null) {
				head = node;
				tail = node;
				return;
			} else {
				tail.setNext(node);
				node.setPrev(tail);
				tail = node;
			}
		}


		public int length() {
			Node current = head;
			int size = 0;
			while (current != null) {
				size++;
				current = current.getNext();
			}
			return size;
		}


		public boolean isEmpty() {
			if(count == 0)
				return true;
			else
				return false;
		}



		public String toString() {
			String result = "head -->";
			Node current = head;
			while (current != null) {
				if (current.getNext() == null)
					result += current + " -->";
				else
					result += current + " <--> ";
				current = current.getNext();
			}
			return result + " null";
		}



		 public void deleteHead(){
			 if(count==0)
				 System.out.println("empty");
			 else{
				 head=head.next;
				 count--;
			 }
		 }
		 public void deleteTail(){
			 if(count==0)
				 System.out.println("the list is empty");
			 else{
				 Node current=head;
				 while(current.next!=tail){
					 current=current.next;
				 }
					 current.next=null;
					 tail=current;

					count--;
			 }
		 }

		 	public void deleteP(int index){
		 		if(index==0)
		 			deleteHead();
		 		else
		 			if(index==count)
		 				deleteTail();
		 			else{
		 				Node current=head;
		 			for(int i=0; i<index-1;i++){
		 				current=current.next;

		 			}
		 			current.next=current.next.next;
		 			count--;
		         	}

           }







}