class MinTimestampTracker implements TimestampTracker<E> {

    public void removeElement(final Stamped<E> elem) {
        if (elem == null) {
            return;
        }

        if (ascendingSubsequence.peekFirst() == elem) {
            ascendingSubsequence.removeFirst();
        }

        if (ascendingSubsequence.isEmpty()) {
            lastKnownTime = elem.timestamp;
        }

    }

}