code: public Row<T>[] getFrequentItems(final long threshold, final ErrorType errorType) {
      return sortItems(threshold > getMaximumError() ? threshold : getMaximumError(), errorType);
    }
docs: Returns an array of Rows that include frequent items, estimates, upper and lower bounds
  given a threshold and an ErrorCondition. If the threshold is lower than getMaximumError(),
  then getMaximumError() will be used instead.
  
  <p>The method first examines all active items in the sketch (items that have a counter).
  
  <p>If <i>ErrorType = NO_FALSE_NEGATIVES</i>, this will include an item in the result
  list if getUpperBound(item) &gt; threshold.
  There will be no false negatives, i.e., no Type II error.
  There may be items in the set with true frequencies less than the threshold
  (false positives).</p>
  
  <p>If <i>ErrorType = NO_FALSE_POSITIVES</i>, this will include an item in the result
  list if getLowerBound(item) &gt; threshold.
  There will be no false positives, i.e., no Type I error.
  There may be items omitted from the set with true frequencies greater than the
  threshold (false negatives).</p>
  
  @param threshold to include items in the result list
  @param errorType determines whether no false positives or no false negatives are
  desired.
  @return an array of frequent items