Is there a way I can make this easily run in constant time instead of linear time?

I am new to java algorithms and doubly linked list. I have been playing around with them quite a lot trying to learn. What would be the best way to make this algorithm run in O(1) instead of O(n) (its a doubly linked list)? I appreciate any help.

public void add(E e) {
    Node<E> cur = header;
    while(cur.next != trailer) {
        cur = cur.next;
    }
    
    Node<E> newNode = new Node<E>(e, cur, cur.next);
    cur.next = newNode;
    trailer.prev = newNode;
    size++;
}

>Solution :

Change

Node<E> cur = header;
while(cur.next != trailer) {
    cur = cur.next;
}

to

Node<E> cur = trailer.prev;