//solution for http://www.geeksforgeeks.org/pairwise-swap-elements-of-a-given-linked-list-by-changing-links/

SwapLinkedList.java

class SwapLinkedList {
    static SwapLinkedList sll = new SwapLinkedList();
    public static void main(String[] args) {
        // 1->2->3->4->5->6
        Node node6 = sll.new Node(null, 6);
        Node node5 = sll.new Node(node6, 5);
        Node node4 = sll.new Node(node5, 4);
        Node node3 = sll.new Node(node4, 3);
        Node node2 = sll.new Node(node3, 2);
        Node root = sll.new Node(node2, 1);
        if(root != null) {
            root = swapValues(root);
        }
        Node node = root;
        while(node != null) {
            System.out.print(node);
            node = node.next;
        }
    }
    
    public static Node swapValues(Node node) {
        if(node == null || node.next == null) return node;
        Node nextNode = node.next;
        node.next = nextNode.next;
        nextNode.next = node;
        node.next = swapValues(node.next);
        return nextNode;
    }
    
    class Node {
        Node next;
        int value;
        
        public Node(Node next, int value) {
            this.next = next;
            this.value = value;
        }
        
        @Override
        public String toString() {
          return value + "->";  
        }
    }
}