code: public long[] getSamples() {
      if (itemsSeen_ == 0) {
        return null;
      }
      final int numSamples = (int) Math.min(reservoirSize_, itemsSeen_);
      return java.util.Arrays.copyOf(data_, numSamples);
    }
docs: Returns a copy of the items in the reservoir. The returned array length may be smaller than the
  reservoir capacity.
  
  @return A copy of the reservoir array