code: private static String[] extract(List<? extends IGenericMetrics> metrics, Extractor e) {
          List<String> strings = new ArrayList<>(metrics.size());
          for (IGenericMetrics metric : metrics) {
              strings.add(e.extract(metric));
          }
          return strings.toArray(new String[strings.size()]);
      }
docs: Get array of Strings from metrics - one from each with given Extractor.
  @param metrics metrics to extract values from.
  @param e extractor that extracts values
  @return array of corresponding strings.