DoublyLinkedList.java

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

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

public class DoublyLinkedList {
    private Node head;
    private Node tail;
    private int size;

    public DoublyLinkedList() {
        this.head = null;
        this.tail = null;
        this.size = 0;
    }

    // Add node at the beginning of the list
    public void addFirst(int data) {
        Node newNode = new Node(data);
        if (head == null) {
            head = newNode;
            tail = newNode;
        } else {
            newNode.next = head;
            head.prev = newNode;
            head = newNode;
        }
        size++;
    }

    // Add node at the end of the list
    public void addLast(int data) {
        Node newNode = new Node(data);
        if (tail == null) {
            head = newNode;
            tail = newNode;
        } else {
            tail.next = newNode;
            newNode.prev = tail;
            tail = newNode;
        }
        size++;
    }

    // Add node at any given position
    public void addAtAnyPosition(int data, int position) {
        if (position < 0 || position > size) {
            System.out.println("Invalid position");
            return;
        }
        Node newNode = new Node(data);
        if (position == 0) {
            addFirst(data);
        } else if (position == size) {
            addLast(data);
        } else {
            Node current = head;
            for (int i = 0; i < position - 1; i++) {
                current = current.next;
            }
            newNode.next = current.next;
            newNode.prev = current;
            current.next.prev = newNode;
            current.next = newNode;
            size++;
        }
    }

    // Remove node from the beginning of the list
    public void removeFirst() {
        if (head == null) {
            System.out.println("List is empty");
            return;
        }
        if (head == tail) {
            head = null;
            tail = null;
        } else {
            head = head.next;
            head.prev = null;
        }
        size--;
    }

    // Remove node from the end of the list
    public void removeLast() {
        if (tail == null) {
            System.out.println("List is empty");
            return;
        }
        if (head == tail) {
            head = null;
            tail = null;
        } else {
            tail = tail.prev;
            tail.next = null;
        }
        size--;
    }

    // Remove node from any given position
    public void removeAtAnyPosition(int position) {
        if (position < 0 || position >= size) {
            System.out.println("Invalid position");
            return;
        }
        if (position == 0) {
            removeFirst();
        } else if (position == size - 1) {
            removeLast();
        } else {
            Node current = head;
            for (int i = 0; i < position; i++) {
                current = current.next;
            }
            current.prev.next = current.next;
            current.next.prev = current.prev;
            size--;
        }
    }

    // Reverse the doubly linked list
    public void reverse() {
        Node temp = null;
        Node current = head;
        while (current != null) {
            temp = current.prev;
            current.prev = current.next;
            current.next = temp;
            current = current.prev;
        }
        if (temp != null) {
            head = temp.prev;
        }
    }

    // Print the doubly linked list
    public void printList() {
        Node current = head;
        while (current != null) {
            System.out.print(current.data + " ");
            current = current.next;
        }
        System.out.println();
    }

    public static void main(String[] args) {
        DoublyLinkedList list = new DoublyLinkedList();
        list.addFirst(1);
        list.addLast(3);
        list.addAtAnyPosition(2, 1);
        list.printList(); // Output: 1 2 3

        list.removeFirst();
        list.removeLast();
        list.removeAtAnyPosition(0);
        list.printList(); // Output: Empty list

        list.addFirst(3);
        list.addLast(1);
        list.addAtAnyPosition(2, 1);
        list.printList(); // Output: 3 2 1

        list.reverse();
        list.printList(); // Output: 1 2 3 (reversed list)
    }
}