@Override
    public void report() {
        final List<String> busiestActors = new ArrayList<>();
        int highestCount = 0;
        for (final Map.Entry<String, Integer> actorYearToMovieCountEntry : actorYearToMovieCount.entrySet())
            if (actorYearToMovieCountEntry.getValue() > highestCount) {
                busiestActors.clear();
                busiestActors.add(actorYearToMovieCountEntry.getKey());
                highestCount = actorYearToMovieCountEntry.getValue();
            } else if (actorYearToMovieCountEntry.getValue() == highestCount)
                busiestActors.add(actorYearToMovieCountEntry.getKey());
        System.out.println(String.format("Most prolific actor(s) in one year: %s with %d movies.", busiestActors,
                                         highestCount));
    }