code: public void add(Distribution anotherDistribution) {
          if (anotherDistribution != null) {
              numValues += anotherDistribution.numValues;
              sumValues += anotherDistribution.sumValues;
              sumSquareValues += anotherDistribution.sumSquareValues;
              minValue = (minValue < anotherDistribution.minValue) ? minValue
                      : anotherDistribution.minValue;
              maxValue = (maxValue > anotherDistribution.maxValue) ? maxValue
                      : anotherDistribution.maxValue;
          }
      }
docs: Add another {@link Distribution}'s values to this one.
  
  @param anotherDistribution
  the other {@link Distribution} instance