code: public Period multipliedBy(int scalar) {
          if (this == ZERO || scalar == 1) {
              return this;
          }
          return create(
                  Math.multiplyExact(years, scalar),
                  Math.multiplyExact(months, scalar),
                  Math.multiplyExact(days, scalar));
      }
docs: Returns a new instance with each element in this period multiplied
  by the specified scalar.
  <p>
  This returns a period with each of the years, months and days units
  individually multiplied.
  For example, a period of "2 years, -3 months and 4 days" multiplied by
  3 will return "6 years, -9 months and 12 days".
  No normalization is performed.
  
  @param scalar  the scalar to multiply by, not null
  @return a {@code Period} based on this period with the amounts multiplied by the scalar, not null
  @throws ArithmeticException if numeric overflow occurs