Java: LinkedList Insertion returns 'list is empty'

Question

I am trying to build LinkedList from scratch for my class. The code is here below.

I am facing this problem: when I want to insert a data, I got the message The list is empty. Did I define the Node variables (current, head, tail, prev, next) in a wrong way, so the node.current is always null?

import java.util.Scanner;

public class DoubleLL {

    public static class Node {

        public String name;
        public Node prev;
        public Node next;
    }

    public static boolean isListEmpty(Node head) {
        if (head == null) {
            return true;
        } else {
            return false;
        }
    }

    public static void addFirstElement(Node head, Node tail, String Nama) {
        Node temp = new Node();
        temp.name = Nama;
        temp.prev = null;
        temp.next = null;
        head = temp;
        tail = temp;
    }

    public static void addFirst(Node head, Node tail, String Nama) { // add data from first element
        if (isListEmpty(head)) {
            addFirstElement(head, tail, Nama);
        } else {
            Node temp = new Node();
            Node q = new Node();
            q = head;
            temp.name = Nama;
            q.prev = temp;
            head = temp;
            temp.next = q;
            temp.prev = null;
        }
    }

    public static void addLast(Node head, Node tail, String Nama) { // add data from last element
        if (isListEmpty(head)) {
            addFirstElement(head, tail, Nama);
        } else {
            Node temp = new Node();
            Node q = new Node();

            q = tail;
            temp.name = Nama;
            q.next = temp;
            tail = temp;
            temp.prev = q;
            temp.next = null;
        }
    }

    public static void deleteFirst(Node head, Node tail) { //delete from first element
        if (isListEmpty(head)) {
            System.out.print("This list is already empty!");
            System.out.print("\n");
        } else if (head == tail) {
            head = null;
            tail = null;
        } else {
            Node temp = head;
            head = head.next;
            head.prev = null;
            temp = null;
        }
    }

    public static void deleteLast(Node head, Node tail) { // delete from last element
        if (isListEmpty(head)) {
            System.out.print("This list is already empty!");
            System.out.print("\n");
        } else if (head == tail) {
            head = null;
            tail = null;
        } else {
            Node temp = tail;
            tail = tail.prev;
            tail.next = null;
            temp = null;
        }
    }

    public static void retrieve(Node current) {
        if (isListEmpty(current)) {
            System.out.print("The list is empty.");
            System.out.print("\n");
        } else {
            System.out.print("The linked list values are : ");
            System.out.print("\n");
            while (current != null) {
                System.out.print(current.name);
                System.out.print("\n");
                current = current.next;
            }
        }
    }

    public static void main(String[] args) {
        int menu;
        String nameMhs;
        Node head = null;
        Node tail = null;

        do {
            System.out.print("Menu Linked List : \n");
            System.out.print("1. Add First\n");
            System.out.print("2. Add Last\n");
            System.out.print("3. Delete First\n");
            System.out.print("4. Delete Last\n");
            System.out.print("5. Retrieve Linked List Values\n");
            System.out.print("6. Exit\n");
            System.out.print("Your choice : ");
            menu = new Scanner(System.in).nextInt();

            switch (menu) {
                case 1:
                    System.out.print("Insert name : ");
                    namaMhs = new Scanner(System.in).nextLine();
                    addFirst(head, tail, nameMhs);
                    break;
                case 2:
                    System.out.print("Insert name: ");
                    namaMhs = new Scanner(System.in).nextLine();
                    addLast(head, tail, nameMhs);
                    break;
                case 3:
                    deleteFirst(head, tail);
                    break;
                case 4:
                    deleteLast(head, tail);
                    break;
                case 5:
                    retrieve(head);
                    break;
                default:
                    System.out.println("Closed.");
            }

            System.out.print("\n");
        } while (menu != 6 && menu < 6);
    }
}