Double Linked List Program in Java

 import java.util.*;  
 class node  
 {  
      int data;  
      node left;  
      node right;  
      node(int d, node l,node r)  
      {  
           data=d;  
           left=l;  
           right=r;  
      }  
 }  
 class Link  
 {  
      node head;  
      node tail;  
      public void insertfront(int data)  
      {  
           int flag=0;  
           node newnode=new node(data,null,null);  
           if (head==null)  
           {  
                head=newnode;  
                tail=head;  
                tail.right=head;  
                head.left=tail;  
                flag=1;  
           }  
           else   
           {  
                newnode.right=head;  
                newnode.left=tail;  
                tail.right=newnode;  
                head=newnode;  
                flag=1;  
           }       
           if (flag==1)  
           {  
                System.out.println("element "+data+"is inserted.");  
           }  
           else  
                System.out.println("element "+data+"is not inserted.");  
      }  
      public void insertend(int data)  
      {  
           node newnode=new node(data,null,null);  
           node current=head;  
           while (current.right!=head)  
           {  
                current=current.right;  
           }  
           current.right=newnode;  
           newnode.left=current;  
           newnode.right=head;  
           tail=newnode;  
      }  
      public void insertatPosition(int data, int pos)  
      {  
           node newnode=new node(data,null,null);  
           node current=head;  
           node previous=head;  
           int i=1;  
           while (i!=(pos-1))  
           {  
                current=current.right;  
                i++;  
           }  
           newnode.right=current.right;  
           newnode.left=current;  
           current.right=newnode;  
           //current=current.right;  
      }  
      public void display()  
      {  
           node current=head;  
           do  
           {  
                     System.out.print("     "+current.data);  
                     current=current.right;  
           }while (current!=head);  
                System.out.println();  
      }  
 }  
 class Circular_Double   
 {  
      public static void main(String[] args)   
      {  
           Scanner scan=new Scanner(System.in);  
           Link obj=new Link();  
           while (true)  
           {  
                System.out.println("*******Please select the option.*********");  
                System.out.println("\t1.Insert the element at first in the list."  
                                         +"\n\t2.Insert at element at end."  
                                         +"\n\t3.Insert element at certain positon."  
                                         +"\n\t4.Insert element at last."  
                                         +"\n\t5.Delete the element."  
                                         +"\n\t6.Search element."  
                                         +"\n\t7.display the Linked list."  
                                         +"\n\t8.Exit from the program.");  
       int num=scan.nextInt();  
                switch (num)  
                {  
                case 1:  
                     System.out.println("Insert the element.");  
                  int n=scan.nextInt();  
                     obj.insertfront(n);  
                     break;  
                case 2:  
                     System.out.println("Insert the element.");  
                  n=scan.nextInt();  
                     obj.insertend(n);  
                     break;  
                case 3:  
                     System.out.println("Insert the element.");  
                  n=scan.nextInt();  
                     System.out.println("POSITION");  
                  int p=scan.nextInt();  
                     obj.insertatPosition(n,p);  
                     break;  
             case 7:  
         obj.display();  
                     break;  
                case 8:  
                     System.exit(0);  
                break;  
                default :  
                     System.out.println("U entered invalied data.So,enter valied data.");  
                }  
           }  
      }  
 }