@Override
    public boolean add(E o) {
        Node<E> next = tail;
        while (next.prev != head) {
            Node<E> prev = next.prev;
            int comp = compare(o, prev.value);
            if (comp > 0) {
                next.prev = prev.next = new Node<>(o, next, prev);
                size++;
                return true;
            } else if (comp == 0) {
                return false;
            }
            next = next.prev;
        }
        // if we haven't returned yet, this is less than
        next.prev = head.next = new Node<>(o, next, head);
        size++;
        return true;
    }
@see java.util.AbstractCollection#add(java.lang.Object)
src/nu/validator/collections/TailBiasedSortedSet.java