code: @Nullable
      private static DoubleSummaryStats processContentTimestamps(List<Long> contentTimestamps)
      {
          requireNonNull(contentTimestamps, "contentTimestamps is null");
  
          // no content (HTTP 204) or there was a single response chunk (so no interarrival time)
          if (contentTimestamps.size() == 0 || contentTimestamps.size() == 1) {
              return null;
          }
  
          DoubleSummaryStatistics statistics = new DoubleSummaryStatistics();
          long previousTimestamp = contentTimestamps.get(0);
          for (int i = 1; i < contentTimestamps.size(); i++) {
              long timestamp = contentTimestamps.get(i);
              statistics.accept(NANOSECONDS.toMillis(timestamp - previousTimestamp));
              previousTimestamp = timestamp;
          }
          return new DoubleSummaryStats(statistics);
      }
docs: Calculate the summary statistics for the interarrival time of the onResponseContent callbacks.