/**
     * Checks, whether the current list contains an element, representing the
     * given topic.
     *
     * @param topic
     *            The topic, for which an representative element in the current
     *            list is searched for.
     * @return Returns true if the given topic is represented by an element of
     *         the current list, otherwise false.
     */
    public boolean contains(Topic topic) {
        if (start == null) {
            return false;
        } else {
            return start.searchInterest(topic) != null;
        }

    }