Insertion of Doubly Link List at Specific Location

package DataS;

import java.util.HashSet;
import java.util.Set;

public class Insertion_Doubly_Linked_Specific_Location {
    Node head;
    Node tail;
    Set<Integer> uniqueNumbers;
    
 

    public class Node {
        int data;
        Node next;
        Node prev;

        public Node(int data) {
            this.data = data;
            this.next = null;
            this.prev = null;
        }
    }


    public Insertion_Doubly_Linked_Specific_Location() {
        this.head = null;
        this.tail = null;
        this.uniqueNumbers = new HashSet<>();
    }

    public void insert(int data) {
        if (uniqueNumbers.contains(data)) {
            System.out.println("This number already exists in the list: " + data);
            return;
        }

        Node newNode = new Node(data);
        uniqueNumbers.add(data);

        if (head == null) {
            head = newNode;
            tail = newNode;
        } else {
            tail.next = newNode;
            newNode.prev = tail;
            tail = newNode;
        }
    }

    public void insertAtPosition(int data, int position) {
        if (uniqueNumbers.contains(data)) {
            System.out.println("This number already exists in the list: " + data);
            return;
        }

        Node newNode = new Node(data);
        uniqueNumbers.add(data);

        if (position == 0) {
            newNode.next = head;
            if (head != null) {
                head.prev = newNode;
            }
            head = newNode;
            if (tail == null) {
                tail = newNode;
            }
            return;
        }

        Node current = head;
        int index = 0;
        while (current != null && index < position - 1) {
            current = current.next;
            index++;
        }

        if (current == null) {
            System.out.println("Position out of bounds");
            return;
        }

        newNode.next = current.next;
        if (current.next != null) {
            current.next.prev = newNode;
        }
        current.next = newNode;
        newNode.prev = current;

        if (newNode.next == null) {
            tail = newNode;
        }
    }

    public void displayForward() {
        Node current = head;
        while (current != null) {
            System.out.print(current.data + " ");
            current = current.next;
        }
        System.out.println();
    }

    public void displayBackward() {
        Node current = tail;
        while (current != null) {
            System.out.print(current.data + " ");
            current = current.prev;
        }
        System.out.println();
    }

    public static void main(String[] args) {
        Insertion_Doubly_Linked_Specific_Location dll = new Insertion_Doubly_Linked_Specific_Location();

        dll.insert(10);
        dll.insert(20);
        dll.insert(30);
        dll.insert(10); // This should print a message that the number already exists

        dll.insertAtPosition(15, 1); // Insert 15 at position 1
        dll.insertAtPosition(25, 3); // Insert 25 at position 3
        dll.insertAtPosition(35, 10); // This should print "Position out of bounds"

        System.out.println("Display Forward:");
        dll.displayForward();

        System.out.println("Display Backward:");
        dll.displayBackward();
    }
}