Anticlockwise spiral conversion of doubly linked list in java

Java program for Anticlockwise spiral conversion of doubly linked list. Here problem description and explanation.

// Java program for
// Convert a doubly linked list anticlockwise spiral form

// This is Linked List Node
class LinkNode
{
    public int data;
    public LinkNode next;
    public LinkNode prev;
    public LinkNode(int data)
    {
        this.data = data;
        this.next = null;
        this.prev = null;
    }
}
public class DoublyLinkedList
{
    public LinkNode head;
    public LinkNode tail;
    public DoublyLinkedList()
    {
        // Set head and tail
        this.head = null;
        this.tail = null;
    }
    // Insert new node at end position
    public void insert(int value)
    {
        // Create a node
        LinkNode node = new LinkNode(value);
        if (this.head == null)
        {
            // Add first node
            this.head = node;
            this.tail = node;
            return;
        }
        // Add node at last position
        this.tail.next = node;
        node.prev = this.tail;
        this.tail = node;
    }
    // Display node element of doubly linked list
    public void display()
    {
        if (this.head == null)
        {
            System.out.println("Empty Linked List");
        }
        else
        {
            System.out.print("Linked List Head to Tail :");
            // Get first node of linked list
            LinkNode temp = this.head;
            // iterate linked list 
            while (temp != null)
            {
                // Display node value
                System.out.print("  " + temp.data);
                // Visit to next node
                temp = temp.next;
            }
            System.out.print("\nLinked List Tail to Head :");
            // Get last node of linked list
            temp = this.tail;
            // iterate linked list 
            while (temp != null)
            {
                // Display node value
                System.out.print("  " + temp.data);
                // Visit to prev node
                temp = temp.prev;
            }
        }
    }
    public void spiralTransform()
    {
        if (this.head == null || this.head.next == null)
        {
            return;
        }
        LinkNode last = this.tail;
        LinkNode current = this.head;
        LinkNode auxiliary = null;
        LinkNode temp = null, back = null;
        // Set new head
        this.head = this.tail;
        while (current != null && last != null)
        {
            if (current == last)
            {
                current.next = null;
                current.prev = back;
                this.tail = current;
                // Set new last node
                return;
            }
            else if (current.next == last)
            {
                current.next = null;
                current.prev = last;
                last.next = current;
                last.prev = back;
                // Set new last node
                this.tail = current;
                return;
            }
            // Swap link
            auxiliary = current.next;
            temp = last.prev;
            current.prev = last;
            last.next = current;
            current.next = temp;
            last.prev = back;
            back = current;
            current = auxiliary;
            last = temp;
        }
    }
    public static void main(String[] args)
    {
        DoublyLinkedList dll = new DoublyLinkedList();
        // Insert following linked list nodes
        dll.insert(1);
        dll.insert(2);
        dll.insert(3);
        dll.insert(4);
        dll.insert(5);
        dll.insert(6);
        dll.insert(7);
        dll.insert(8);
        dll.insert(9);
        System.out.println("\nBefore anticlockwise spiral conversion");
        // Display all node
        dll.display();
        System.out.println("\nAfter anticlockwise spiral conversion");
        dll.spiralTransform();
        dll.display();
    }
}

Output

Before anticlockwise spiral conversion
Linked List Head to Tail :  1  2  3  4  5  6  7  8  9
Linked List Tail to Head :  9  8  7  6  5  4  3  2  1
After anticlockwise spiral conversion
Linked List Head to Tail :  9  1  8  2  7  3  6  4  5
Linked List Tail to Head :  5  4  6  3  7  2  8  1  9