DoublyLinkedList

Add Node at front:

public void addNodeFront(DoublyLinkedList doublyLinkedList, int nData) {
Node newNode = new Node(nData);
Node current = doublyLinkedList.first;
if (first == null)
first = newNode;
else {
first.previous = newNode;
newNode.next = first;
first = newNode;
}
}

Add Node at end:

public void addNode(int nData) {

Node newNode = new Node(nData);
Node current = first;
if (first == null)
first = newNode;
else {
while (current.next != null) {
current = current.next;
}
current.next = newNode;
newNode.next = null;
newNode.previous = current;
}
}

Delete Node at specific Index:

   public Node deleteItem(int data){
  Node current = first;
  while (current.nData!=data) {
  current = current.next;
}
  if(current.next!=null){
  current.next.previous = current.previous;
  current.previous.next = current.next;
  }
  else
current.previous.next = null;
  return current;
   }