Question

Exercise 2:
Write a program in Java to manipulate a Double Linked List:

1. Create Double Linked List
2. Display the list
3. Count the number of nodes
4. Insert a new node at the beginning of a Double Linked List.
5. Insert a new node at the end of a DoubleLinked List
6. Insert a new node after the value 5 of Double Linked List
7. Delete the node with value 6.
8. Search an existing element in a Double linked list (the element of search is given by the user)
9. Call all methods above in main method with the following data:

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

Answer 1

Here is you full complete java code to manipulate Doubly Linked List:

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import java.util.Scanner;

class node
{
   int data;
   node next;
   node prev;
   node(int x)
   {
       data = x;
   }
  
}

public class DoublyLinkedList {
   node head=null;
   void insert_end(node newnode)
   {
       if(head==null)
       {
           head= newnode;
           head.next=null;
           head.prev=null;
       }
       else
       {
           node temp = head;
           node prev = head;
           while(temp!=null)
           {
               prev= temp;
               temp=temp.next;
           }
           prev.next = newnode;
           newnode.prev = prev;
           newnode.next = null;
       }
   }
   void insert_begin(node newnode)
   {
       newnode.next = head;
       head.prev= newnode;
       newnode.prev=null;
       head = newnode;
      
   }
   void insert_after(node newnode,int after)
   {
       node temp = head;
       node prev = head;
       while(prev.data != after && temp!=null)
       {
           prev= temp;
           temp=temp.next;
       }
       prev.next = newnode;
       newnode.prev = prev;
       newnode.next = temp;
       if(temp!=null)
       temp.prev =newnode;
   }
   void display()
   {
       System.out.println();
       System.out.println("**********LIST IS********");
       node temp = head;
       while(temp!=null)
       {
           System.out.print(temp.data+"->");
           temp=temp.next;
       }
       System.out.println("end");
       System.out.println();
   }
   int get_length()
   {
       int count=0;
       node temp = head;
       while(temp!=null)
       {
           count++;
           temp=temp.next;
       }
       return count;
   }
   void search(int search_this)
   {
       node temp = head;
       int i=0;
       while(temp!=null)
       {
           if(temp.data == search_this)
           System.out.println(temp.data+" at "+(i)+" index");
          
           temp = temp.next;
           i++;
       }
   }
   void delete(int delete_this)
   {
       node temp = head;
       node prev= head;
       int i=0;
       if(temp.data == delete_this)
       {
           temp.next.prev = null;
           head = temp.next;
           return;
       }
      
       while(temp!=null)
       {
          
           if(temp.data == delete_this)
           {
               prev.next = temp.next;
               temp.next.prev = prev;
               return;
           }
           prev= temp;
           temp= temp.next;
           i++;
       }
       System.out.println("Node not found");
   }
   public static void main(String[] args) {
       // TODO Auto-generated method stub
      
       Scanner cin = new Scanner(System.in);
       System.out.println("Enter the number of nodes");
       int n = cin.nextInt();
       int x,i=0;
       DoublyLinkedList list = new DoublyLinkedList();
       while(i!=n)
       {
           System.out.println("Enter data for "+(i+1)+" node: ");
           x = cin.nextInt();
           node newnode = new node(x);
           list.insert_end(newnode);
          
          
          
           i++;
       }
       list.display();
       System.out.println("Length of the list is: "+ list.get_length());
      
       System.out.println("Enter data to insert at begin: ");
       x = cin.nextInt();
       node newnode = new node(x);
       list.insert_begin(newnode);
       list.display();
      
       System.out.println("Enter data to insert in between: ");
       x= cin.nextInt();
       newnode = new node(x);
       System.out.println("after which data? : ");
       int after = cin.nextInt();
       list.insert_after(newnode,after);
       list.display();
      
       System.out.println("-----now deleting node with data 6----");
       list.delete(6);
       list.display();
      
       System.out.println("Enter data to search for: ");
       int search_this = cin.nextInt();
       list.search(search_this);
   }

}
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Output:

Screenshot 1:

Screenshot 2:

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Note:

1. The above program has two classes one Node which defines the structure or properties of a node of doubly linked list and the other class is DoublyLinkedList which has head pointer as a member and other utility functions which manages the doubly linked list.
2. Main() of the class DoublyLinkedList is the driver for the above code which includes all the test data mentioned in the problem plus additional test data added by me to verify other functions/operations on doubly linked list.
3. Searching of an element gives you output position of an element on basis of 0- indexing.  

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I hope this helps you. Good luck.

Edit:

Screenshots of the code:

Screenshot 1:

Screenshot 2:

Screenshot 3:

Screenshot 4:

Screenshot 5: