Public class DLL{     public DLLNode first;    public DLLNode last;    public DLL()          {this.first=Null;           this.last=Null;} Public void Display() {if (first==Null)        {s.o.p(“ the list is empty”);} else {for (DLLNode curr=first; curr!=Null; curr=curr.succ) {System.out.println(“the element is”+ curr.element); }} Public void AddBegining(DLLNode Node) {Node.succ=first; First.prev=Node First=Node; Node.prev=Null; if(first ==null && last==null) Last=node; } Public void Append(DLLNode Node) {Node.succ=Null;  if(first==Null) {first=Node; Node.prev=Null}   Public void insetAfter(int obj, DLLNode Node) {DLLNode curr=first;     while((curr!=Null)&&( curr.element!=obj))    { curr=curr.succ; }   If(curr.element==obj) {Node.succ=curr.succ; Curr.succ.prev=Node; Curr.succ=Node; Node.prev=curr;} Else System.out.println(“the element doesn’t exist”); Public void delete(DLLNode del) {   if(first==Null)   {System.out.println(“the list is empty”); } Else if(del==first)  {first==del.succ;} Else if(del.succ==Null)   first=Null;    last=Null; Else {DLLNode ptr= first; while(ptr.succ!=del) {Ptr=ptr.succ;} Public class DLLNode{   int element;   DLLNode prev;   DLLNode succ; Public DLLNode(int E) {this. Element=E; This. prev=Null; This.succ=Null} Public static void main(String args[]) {DLL list = new DLL(); Scanner s = new Scanner(System.in); Int X,Y,Size; DLLNode Node1= new DLLNode(5); DLLNode Node2= new DLLNode(6); DLLNode Node3= new DLLNode(7); DLLNode Node4= new DLLNode(9); list.AddBegining(Node1); list.Append(Node2); list.Append(Node3); list.Append(Node4); list.Display(); 1. Count the number of nodes 2. Insert a new node before the value 7 of Double Linked List 3. Search an existing element in a Double linked list (the element of search is given by the user) Suppose List contained the following Test Data: Input the number of nodes : 4 Input data for node 1 : 5 Input data for node 2 : 6 Input data for node 3 : 7 Input data for node 4: 9

Public class DLL{

    public DLLNode first;

   public DLLNode last;

   public DLL()

         {this.first=Null;

          this.last=Null;}

Public void Display()

{if (first==Null)

       {s.o.p(“ the list is empty”);}

else

{for (DLLNode curr=first; curr!=Null; curr=curr.succ)

{System.out.println(“the element is”+ curr.element);

}}

Public void AddBegining(DLLNode Node)

{Node.succ=first;

First.prev=Node

First=Node;

Node.prev=Null;

if(first ==null && last==null)

Last=node;

}

Public void Append(DLLNode Node)

{Node.succ=Null;

 if(first==Null)

{first=Node;

Node.prev=Null}

Public void insetAfter(int obj, DLLNode Node)

{DLLNode curr=first;

    while((curr!=Null)&&( curr.element!=obj))

   { curr=curr.succ; }

If(curr.element==obj)

{Node.succ=curr.succ;

Curr.succ.prev=Node;

Curr.succ=Node;

Node.prev=curr;}

Else

System.out.println(“the element doesn’t exist”);

Public void delete(DLLNode del)

{

  if(first==Null)

  {System.out.println(“the list is empty”); }

Else if(del==first)

 {first==del.succ;}

Else if(del.succ==Null)

  first=Null;

   last=Null;

Else

{DLLNode ptr= first;

while(ptr.succ!=del)

{Ptr=ptr.succ;}

Public class DLLNode{

  int element;

  DLLNode prev;

  DLLNode succ;

Public DLLNode(int E)

{this. Element=E;

This. prev=Null;

This.succ=Null}

Public static void main(String args[])

{DLL list = new DLL();

Scanner s = new Scanner(System.in);

Int X,Y,Size;

DLLNode Node1= new DLLNode(5);

DLLNode Node2= new DLLNode(6);

DLLNode Node3= new DLLNode(7);

DLLNode Node4= new DLLNode(9);

list.AddBegining(Node1);

list.Append(Node2);

list.Append(Node3);

list.Append(Node4);

list.Display();

1. Count the number of nodes
2. Insert a new node before the value 7 of Double Linked List
3. Search an existing element in a Double linked list (the element of search
is given by the user)
Suppose List contained the following Test Data: Input the number of nodes : 4
Input data for node 1 : 5
Input data for node 2 : 6
Input data for node 3 : 7 Input data for node 4: 9