Java Algorithm – Pairwise swap elements of a given linked list

// Java program to pairwise swap elements of a linked list
class LinkedList
{
    Node head;  // head of list
  
    /* Linked list Node*/
    class Node
    {
        int data;
        Node next;
        Node(int d) {data = d; next = null; }
    }
 
    void pairWiseSwap()
    {
        Node temp = head;
 
        /* Traverse only till there are atleast 2 nodes left */
        while (temp != null && temp.next != null) {
 
            /* Swap the data */
            int k = temp.data;
            temp.data = temp.next.data;
            temp.next.data = k;
            temp = temp.next.next;
         }
    }
 
                     
    /* Utility functions */
 
    /* Inserts a new Node at front of the list. */
    public void push(int new_data)
    {
        /* 1 & 2: Allocate the Node &
                  Put in the data*/
        Node new_node = new Node(new_data);
  
        /* 3. Make next of new Node as head */
        new_node.next = head;
  
        /* 4. Move the head to point to new Node */
        head = new_node;
    }
 
    /* Function to print linked list */
    void printList()
    {
        Node temp = head;
        while (temp != null)
        {
           System.out.print(temp.data+" ");
           temp = temp.next;
        }  
        System.out.println();
    }
 
    /* Driver program to test above functions */
    public static void main(String args[])
    {
        LinkedList llist = new LinkedList();
 
        /* Created Linked List 1->2->3->4->5 */
        llist.push(5);
        llist.push(4);
        llist.push(3);
        llist.push(2);
        llist.push(1);
         
        System.out.println("Linked List before calling pairWiseSwap() ");
        llist.printList();
         
        llist.pairWiseSwap();
         
        System.out.println("Linked List after calling pairWiseSwap() ");
        llist.printList();
    }
} 
/* This code is contributed by Rajat Mishra */