Question

Using a doubly linked list, create a list L1 with words from a text file in Java.

Answer 1

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class FileWords {

    public static void main(String[] args) throws FileNotFoundException {
        String fileName = "input.txt";

        Scanner reader = new Scanner(new File(fileName));

        DoublyLinkedList<String> list = new DoublyLinkedList<>();
        while(reader.hasNext()) {
            list.addLast(reader.next());
        }

        list.display();

        reader.close();
    }

}

=====================

public class DoublyLinkedList<E> {
    private Node<E> header;
    private Node<E> trailer;
    private int size = 0;

    public DoublyLinkedList() {
        header = null;
        trailer = null;
    }

    public int size() {
        return size;
    }

    public boolean isEmpty() {
        return size == 0;
    }

    public E first() {
        if (isEmpty())
            return null;
        return header.getElement();
    }

    public E last() {
        if (isEmpty())
            return null;
        return trailer.getElement();
    }

    private void addBetween(E e, Node<E> predecessor, Node<E> successor) {
        Node<E> newest = new Node<>(e, predecessor, successor);
        if(predecessor == null) {
            header = newest;
        } else {
            predecessor.setNext(newest);
        }

        if(successor == null) {
            trailer = newest;
        } else {
            successor.setPrev(newest);
        }
        size++;
    }

    private E remove(Node<E> e) {
        Node<E> predecessor = e.getPrev();
        Node<E> successor = e.getNext();
        if(predecessor == null) {
            header = successor;
        } else {
            predecessor.setNext(successor);
        }
        if(successor == null) {
            trailer = predecessor;
        } else {
            successor.setPrev(predecessor);
        }
        size--;
        if(size == 0) {
            header = trailer = null;
        }
        return e.getElement();
    }

    public void addFirst(E e) {
        if(header == null) {
            addBetween(e, null, null);
        } else {
            addBetween(e, header, header.getNext());
        }
    }

    public void addLast(E e) {
        if(trailer == null) {
            addBetween(e, null, null);
        } else {
            addBetween(e, trailer.getPrev(), trailer);
        }
    }

    public E removeFirst() {
        if (isEmpty())
            return null;
        return remove(header);

    }

    public E removeLast() {
        if (isEmpty())
            return null;
        return remove(trailer);

    }

    public void reverse() {
        if(isEmpty() || header == trailer) {
            return;
        }
        Node<E> prev = null;
        Node<E> start = header;
        while(start != null) {
            Node<E> next = start.next;
            start.next = prev;
            start.prev = next;
            prev = start;
            start = next;
        }
        trailer = header;
        header = prev; 
    }

    public void display() {
        Node<E> start = header;
        while(start != null) {
            System.out.print(start.element + " ");
            start = start.next;
        }
        System.out.println();
    }

    private static class Node<E> {
        private E element;
        private Node<E> next;
        private Node<E> prev;

        public Node(E e, Node<E> p, Node<E> n) {
            element = e;
            prev = p;
            next = n;
        }

        public E getElement() {
            return element;
        }

        public Node<E> getPrev() {
            return prev;
        }

        public Node<E> getNext() {
            return next;
        }

        public void setPrev(Node<E> n) {
            prev = n;
        }

        public void setNext(Node<E> n) {
            next = n;
        }

    }
}

Please upvote, as i have given the exact answer as asked in question. Still in case of any concerns in code, let me know in comments. Thanks!