DoubleLinklist.java

public class DoubleLinklist {
    class Node {
        String data;
        Node next;
        Node prev;
        public Node(String data) {
            this.data = data;
            this.next = null;
            this.prev = null;
        }
    }
    private Node head;
    private Node tail;
    public void AddFirst(String data) {
        Node newNode = new Node(data);
        if (head == null) {
            head = tail = newNode;
        }
        else {
            newNode.next = head;
            head.prev = newNode;
            head = newNode;
        }
    }
    public void AddLast(String data) {
        Node newNode = new Node(data);
        if (head == null) {
            head = tail = newNode;
        }
        else {
            tail.next = newNode;
            newNode.prev = tail;
            tail = newNode;
        }
    }
    public boolean insert(String data, int index) {
        if (index < 0 || index > data.length()) {
            System.out.println("Invalid index");
            return false;
        }
        if (index == 0) {
            AddFirst(data);
            return true;
        }
        Node newNode = new Node(data);
        Node current = head;
        int currentIndex = 0;
        while (current != null && currentIndex < index - 1) {
            current = current.next;
            currentIndex++;
        }
        if (current == null) {
            return false;
        }
        newNode.next = current.next;
        if (current.next != null) {
            current.next.prev = newNode;
        }
        current.next = newNode;
        newNode.prev = current;
        if(newNode.next == null){
            tail = newNode;
        }
        return true;
    }
    public void remove(String value) {
        if (head == null) return;

        Node current = head;
        while (current != null) {
            if (current.data.equals(value)) {
                if (current == head) {
                    head = head.next;
                    if (head != null) head.prev = null;
                } else if (current == tail) {
                    tail = tail.prev;
                    if (tail != null) tail.next = null;
                } else {
                    current.prev.next = current.next;
                    current.next.prev = current.prev;
                }
                System.out.println("Елемент '" + value + "' видалено.");
                return;
            }
            current = current.next;
        }
        System.out.println("Елемент '" + value + "' не знайдено.");
    }
    public void showFromStart(){
        Node current = head;
        while (current != null) {
            System.out.println(current.data + " ");
            current = current.next;
        }
        System.out.println();
    }
    public void showFromEnd(){
        Node current = tail;
        while (current != null) {
            System.out.println(current.data + " ");
            current = current.prev;
        }
        System.out.println();
    }

}