code: public List<T> getFrequentStyles(float factor, int maxfreq)
      {
          List<T> ret = new ArrayList<T>();
          for (Map.Entry<T, Integer> entry : styles.entrySet())
          {
              if (entry.getValue() >= factor * maxfreq)
                  ret.add(entry.getKey());
          }
          return ret;
      }
docs: Obtains the frequent style where the frequency is greater or equal than factor*max_frequency
  where max_frequency may be specified arbitrarily.
  @param factor the frequency factor
  @param maxfreq the maximal frequency equal to factor 1.0
  @return The list of frequent styles