code: public void merge(ExponentialHistogram b) {
      if (b.mergeThreshold != mergeThreshold) {
        throw new IllegalArgumentException();
      }
      merge(b.boxes, b.total);
    }
docs: Merge the supplied ExponentialHistogram in to this one.
  
  @param b histogram to merge
  @throws IllegalArgumentException if the two merge-thresholds are not equals