CODE EXAMPLE FOR JAVA

swap two nodes of a linked list

// Java program to swap two given nodes of a linked list
public class Solution {
 
    // Represent a node of the singly linked list
    class Node {
        int data;
        Node next;
 
        public Node(int data)
        {
            this.data = data;
            this.next = null;
        }
    }
 
    // Represent the head and tail of the singly linked list
    public Node head = null;
    public Node tail = null;
 
    // addNode() will add a new node to the list
    public void addNode(int data)
    {
        // Create a new node
        Node newNode = new Node(data);
 
        // Checks if the list is empty
        if (head == null) {
            // If list is empty, both head and
            // tail will point to new node
            head = newNode;
            tail = newNode;
        }
        else {
            // newNode will be added after tail such that
            // tail's next will point to newNode
            tail.next = newNode;
            // newNode will become new tail of the list
            tail = newNode;
        }
    }
 
    // swap() will swap the given two nodes
    public void swap(int n1, int n2)
    {
        Node prevNode1 = null, prevNode2 = null,
             node1 = head, node2 = head;
 
        // Checks if list is empty
        if (head == null) {
            return;
        }
 
        // If n1 and n2 are equal, then
        // list will remain the same
        if (n1 == n2)
            return;
 
        // Search for node1
        while (node1 != null && node1.data != n1) {
            prevNode1 = node1;
            node1 = node1.next;
        }
 
        // Search for node2
        while (node2 != null && node2.data != n2) {
            prevNode2 = node2;
            node2 = node2.next;
        }
 
        if (node1 != null && node2 != null) {
 
            // If previous node to node1 is not null then,
            // it will point to node2
            if (prevNode1 != null)
                prevNode1.next = node2;
            else
                head = node2;
 
            // If previous node to node2 is not null then,
            // it will point to node1
            if (prevNode2 != null)
                prevNode2.next = node1;
            else
                head = node1;
 
            // Swaps the next nodes of node1 and node2
            Node temp = node1.next;
            node1.next = node2.next;
            node2.next = temp;
        }
        else {
            System.out.println("Swapping is not possible");
        }
    }
 
    // display() will display all the
    // nodes present in the list
    public void display()
    {
        // Node current will point to head
        Node current = head;
 
        if (head == null) {
            System.out.println("List is empty");
            return;
        }
        while (current != null) {
            // Prints each node by incrementing pointer
            System.out.print(current.data + " ");
            current = current.next;
        }
        System.out.println();
    }
 
    public static void main(String[] args)
    {
 
        Solution sList = new Solution();
 
        // Add nodes to the list
        sList.addNode(1);
        sList.addNode(2);
        sList.addNode(3);
        sList.addNode(4);
        sList.addNode(5);
        sList.addNode(6);
        sList.addNode(7);
 
        System.out.println("Original list: ");
        sList.display();
 
        // Swaps the node 2 with node 5
        sList.swap(6, 1);
 
        System.out.println("List after swapping nodes: ");
        sList.display();
    }
}