Add more methods to the doubly linked list class then test them • search(e) // Return one node with 3 values (stuID, stuName, stuScore) which matches a given key e (studentID). • addAfter(e, stuID, stuName, stuScore) //Add a new node with 3 values (stuID, stuName, stuScore) after the node with the key e (studentID). • removeAt(e) //Remove a node which matches a given key e (studentID) • count() //Return a number of nodes of list. • update(stuID, stuName, stuScore) //Update the values of one node two codes below  package DlinkedList; class Node { private A stuID; private B stuName; private C stuScore; private Node next; private Node prev;   public Node(A id, B name, C score) { stuID = id; stuName = name; stuScore = score; next = null; prev = null; } public A getStuID() { return stuID; } public B getStuName() { return stuName;   } public C getStuScore() { return stuScore; } public Node getNext(){ return next; } public Node getPrev(){ return prev; } public void setStuID(A ID) { stuID = ID; } public void setStuName(B name) { stuName = name; }    public void setStuScore(C score) {     stuScore = score;      }   public void setNext(Node n) { next = n; } public void setPrev(Node p) { prev = p; }   public void displayNode() { System.out.println( "ID="+getStuID()+", Name="+getStuName()+", Score="+getStuScore());   } }   package DlinkedList; public class DLinkedList {     private Node header;     private Node trailer;     private int size;          public DLinkedList() {         header = new Node<>(null, null, null);         trailer = new Node<>(null, null, null);         header.setNext(trailer);         trailer.setPrev(header);              }     public int getSize() {         return size;     }     public boolean isEmpty() {         return size==0;     }     public A getFirstStuID() {         return header.getNext().getStuID();     }     public B getFirstStuName() {         return header.getNext().getStuName();     }     public C getFirstStuScore() {         return header.getNext().getStuScore();          }          public A getLastStuID() {         return trailer.getPrev().getStuID();     }     public B getLastStuName() {         return trailer.getPrev().getStuName();     }     public C getLastStuScore() {         return trailer.getPrev().getStuScore();     }          private void addBetween(A id, B name, C score, Node predecessor, Node successor) {         Node newest = new Node<>(id, name, score);         newest.setPrev(predecessor);         newest.setNext(successor);         predecessor.setNext(newest);         successor.setPrev(newest);         size++;         }     public void addFirst(A id, B name, C score) {         addBetween(id, name,score,header,header.getNext());     }     public void addLast(A id, B name, C score) {         addBetween(id, name,score, trailer.getPrev(), trailer);     }     private Node remove(Node node){         Node predecessor = node.getPrev();         Node successor = node.getNext();         predecessor.setNext(successor);         successor.setPrev(predecessor);         size--;         return node;     }     public Node removeFirst(){         if(isEmpty())             return null;         return remove(header.getNext());     }     public Node removeLast(){         if(isEmpty())             return null;         return remove(trailer.getPrev());     }     public Node search(A key){         if(isEmpty())             return null;         Node temp = header.getNext();         do{             if(temp.getStuID()== key)                 return temp;             temp = temp.getNext();             }while ( temp != null);         return null;     }          public void addAfter(A key, A id, B name, C score) {         if(isEmpty())             return;         Node node = search(key);         if(node == null)        return;         addBetween(id, name, score, node, node.getNext());     }          public void display() {         if(isEmpty()) {             System.out.println("Linked list is empty.");             return;         }         Node temp = header.getNext();         do {             temp.displayNode();             temp = temp.getNext();         }while(temp.getNext() !=null);     }     public void addBefore(A key, A id, B name, C score) {         if(isEmpty())             return;         Node node = search(key);         if(node == null)             return;         addBetween( id, name, score, node.getPrev(), node);     }     public Node removeAt( A key){         if (isEmpty())             return null;         Node node = search(key);         if(node == null)             return null;         return remove(node);     }     public Node update(A key, A nid, B nname, C nscore){         if(isEmpty())             return null;         Node node = search(key);         if(node == null)             return null;         node.setStuID(nid);         node.setStuName(nname);         node.setStuScore(nscore);         return node;     } }