code: public static BigDecimal inverse(final BigDecimal value, final int scale) {
          return inverse(value, scale, BigDecimal.ROUND_HALF_UP);
      }
docs: Return the inverse of value if not null or zero, using scale.
  @param value the nullable BigDecimal
  @param scale scale for the result if value is not null
  @return 1 / value (if not null of zero)