Insertion in the middle Doubly Linked List in Java

class LinkedList {
    Node head;

    // Node Class
    class Node {
        int data;
        Node next, prev;

        Node(int x) // parameterized constructor
        {
            data = x;
            next = null;
            prev = null;
        }
    }

    public void insert(int data) {
        Node newNode = new Node(data);
        newNode.next = head;
        newNode.prev = null;

        if (head != null)
            head.prev = newNode;

        head = newNode;
    }

    public void insertMiddle(int data) {
        Node newNode = new Node(data);

        // if the LL was empty
        if (head == null) {
            // using insert function to insert at start
            insert(data);
            return;
        }

        // otherwise
        // find correct insertion position for middle
        int size = findSize();
        int mid = (size % 2 == 0) ? (size / 2) : (size + 1) / 2;

        // will only happen when there is one node in Doubly Linked List
        // we will have to insert at the last,
        // inserting 2nd node at the last
        // Example size = 1 will result in mid = 1 so entering after 1st node
        // where size itself is 1 so entering last node
        if (mid == size) {
            newNode.next = null;
            newNode.prev = head;
            head.next = newNode;
            size++;
            return;
        }

        Node temp = head;
        // traverse to current mid position
        while (--mid > 0) {
            temp = temp.next;
        }

        // (mid+1)th node prev to this newNode
        (temp.next).prev = newNode;
        // newNode's prev to this current middle node
        newNode.prev = temp;
        // newNode's next to (mid+1)th node
        newNode.next = temp.next;
        // current mid node's next becomes this newNode
        temp.next = newNode;
        size++;
    }

    public int findSize() {
        int size = 0;

        Node node = head;

        while (node != null) {
            node = node.next;
            size++;
        }
        return size;
    }

    public void display() {

        Node node = head;
        Node end = null;

        System.out.println("List in forward direction: ");
        while (node != null) {
            System.out.print(node.data + " ");
            end = node;
            node = node.next;
        }
        System.out.println();

        System.out.println("List in backward direction: ");

        while (end != null) {
            System.out.print(end.data + " ");
            end = end.prev;
        }
        System.out.println("\n");
    }
}
public class Main{
    public static void main(String args[])
    {
        LinkedList ll = new LinkedList();

        ll.insert(4);
        ll.insert(0);

        System.out.println("List before insertion");
        ll.display();

        ll.insertMiddle(1);

        System.out.println("List after insertion");
        ll.display();
    }
}

Output

List before insertion
List in forward direction: 
0 4 
List in backward direction: 
4 0 

List after insertion
List in forward direction: 
0 1 4 
List in backward direction: 
4 1 0