code: public Duration multipliedBy(long multiplicand) {
          if (multiplicand == 0) {
              return ZERO;
          }
          if (multiplicand == 1) {
              return this;
          }
          return create(toSeconds().multiply(BigDecimal.valueOf(multiplicand)));
       }
docs: Returns a copy of this duration multiplied by the scalar.
  <p>
  This instance is immutable and unaffected by this method call.
  
  @param multiplicand  the value to multiply the duration by, positive or negative
  @return a {@code Duration} based on this duration multiplied by the specified scalar, not null
  @throws ArithmeticException if numeric overflow occurs