using this--> /**  * Node class used for implementing your LinkedDeque.  *  * DO NOT MODIFY THIS FILE!!  *  */ public class LinkedNode { private T data; private LinkedNode previous; private LinkedNode next; /**  * Creates a new LinkedNode with the given T object and node references.  *  * @param previous the previous node in the list  * @param data the data stored in the new node  * @param next the next node in the list  */  public LinkedNode(LinkedNode previous, T data, LinkedNode next) { this.previous = previous; this.data = data; this.next = next; } /**  * Creates a new LinkedNode with only the given T object.  *  * @param data the data stored in the new node  */  public LinkedNode(T data) { this(null, data, null); } /**  * Gets the data stored in the node.  *  * @return the data in this node  */  public T getData() { return data; } /**  * Gets the next node.  *  * @return the next node  */  public LinkedNode getNext() { return next; } /**  * Sets the next node.  *  * @param next the new next node  */  public void setNext(LinkedNode next) { this.next = next; } /**  * Gets the previous node.  *  * @return the previous node  */  public LinkedNode getPrevious() { return previous; } /**  * Sets the previous node.  *  * @param previous the new previous node  */  public void setPrevious(LinkedNode previous) { this.previous = previous; } @Override public String toString() { return "Node containing: " + data; } }

please complete this:=========================================================================

public class LinkedDeque { // Do not add new instance variables and do not add a new constructor. private LinkedNode head; private LinkedNode tail; private int size; /**  * Adds the data to the front of the deque.  *  * This method must run in O(1) time.  *  * @param data the data to add to the deque  * @throws java.lang.IllegalArgumentException if data is null  */  public void addFirst(T data) { } /**  * Adds the data to the back of the deque.  *  * This method must run in O(1) time.  *  * @param data the data to add to the deque  * @throws java.lang.IllegalArgumentException if data is null  */  public void addLast(T data) { } /**  * Removes the data at the front of the deque.  *  * This method must run in O(1) time.  *  * @return the data formerly at the front of the deque  * @throws java.util.NoSuchElementException if the deque is empty  */  public T removeFirst() { } /**  * Removes the data at the back of the deque.  *  * This method must run in O(1) time.  *  * @return the data formerly at the back of the deque  * @throws java.util.NoSuchElementException if the deque is empty  */  public T removeLast() { } /**  * Returns the number of elements in the deque.  *  * Runs in O(1) for all cases.  *  * DO NOT USE THIS METHOD IN YOUR CODE.  *  * @return the size of the list  */  public int size() { // DO NOT MODIFY! return size; } /**  * Returns the head node of the linked deque.  * Normally, you would not do this, but it's necessary for testing purposes.  *  * DO NOT USE THIS METHOD IN YOUR CODE.  *  * @return node at the head of the linked deque  */  public LinkedNode getHead() { // DO NOT MODIFY! return head; } /**  * Returns the tail node of the linked deque.  * Normally, you would not do this, but it's necessary for testing purposes.  *  * DO NOT USE THIS METHOD IN YOUR CODE.  *  * @return node at the tail of the linked deque  */  public LinkedNode getTail() { // DO NOT MODIFY! return tail; } }