Implement a Doubly linked list to store a set of Integer numbers (no duplicate)  • Instance variable • Constructor • Accessor and Update methods 2. Define DLinkedList Class a. Instance Variables:      # Node header      # Node trailer      # int size b. Constructor c. Methods      # int getSize() //Return the number of nodes of the list.      # int getSize() //Return the number of elements of the list.      # boolean isEmpty() //Return true if the list is empty, and false otherwise.      # E getFirst() //Return the value of the first node of the list.      # E getLast()/ /Return the value of the Last node of the list.      # addFirst(E e) //Add a new node to the front of the list.      # addLast(E e) //Add a new node to the end of the list.      # Node remove(Node n) //remove a node which has the reference n from the list      # Node removeFirst() //Remove the first node of the list, and return the removed node or null if failed.      # Node removeLast() //Remove the last node of the list, and return the removed node or null if failed.      # addBetween(E e, Node predecessor, Node successor) //Add a new node between the predecessor and                   successor.      # Node search(E key) //Search and return a node according to a given key      # Node update(E key, E e) //update the value of a given k to a new value.      # display() //Display all nodes of the list by traversing the linked list.      # addAfter(E e, E key) // Add a new node e after a given key of the list.      # addBefore(E e, E key) // Add a new node e before a given key of the list.      # Node removeAt(E key) //Remove node based on a given key, return the removed node or null if failed

Implement a Doubly linked list to store a set of Integer numbers (no duplicate) 
• Instance variable
• Constructor
• Accessor and Update methods

2. Define DLinkedList Class
a. Instance Variables:
     # Node header
     # Node trailer
     # int size
b. Constructor
c. Methods
     # int getSize() //Return the number of nodes of the list.
     # int getSize() //Return the number of elements of the list.
     # boolean isEmpty() //Return true if the list is empty, and false otherwise.
     # E getFirst() //Return the value of the first node of the list.
     # E getLast()/ /Return the value of the Last node of the list.
     # addFirst(E e) //Add a new node to the front of the list.
     # addLast(E e) //Add a new node to the end of the list.
     # Node remove(Node n) //remove a node which has the reference n from the list
     # Node removeFirst() //Remove the first node of the list, and return the removed node or null if failed.
     # Node removeLast() //Remove the last node of the list, and return the removed node or null if failed.
     # addBetween(E e, Node predecessor, Node successor) //Add a new node between the predecessor and                   successor.
     # Node search(E key) //Search and return a node according to a given key
     # Node update(E key, E e) //update the value of a given k to a new value.
     # display() //Display all nodes of the list by traversing the linked list.
     # addAfter(E e, E key) // Add a new node e after a given key of the list.
     # addBefore(E e, E key) // Add a new node e before a given key of the list.
     # Node removeAt(E key) //Remove node based on a given key, return the removed node or null if failed