code: @Override
      public MonetaryAmount multiply(Number multiplicand) {
          BigDecimal d = toBigDecimal(multiplicand, context);
          if (BigDecimal.ONE.compareTo(d) == 0) {
              return this;
          }
          BigDecimal multiplied = betrag.multiply(d);
          return Geldbetrag.valueOf(multiplied, currency);
      }
docs: Returns a {@code MonetaryAmount} whose value is <tt>(this &times;
  multiplicand)</tt>, and whose scale is <code>this.scale() +
  multiplicand.scale()</code>.
  
  @param multiplicand value to be multiplied by this {@code MonetaryAmount}. If the multiplicand's scale exceeds
  the
  capabilities of the implementation, it may be rounded implicitly.
  @return {@code this * multiplicand}
  @throws ArithmeticException if the result exceeds the numeric capabilities of this implementation class, i.e.
  the {@link MonetaryContext} cannot be adapted as required.