code: public PeriodDuration multipliedBy(int scalar) {
          if (scalar == 1) {
              return this;
          }
          return of(period.multipliedBy(scalar), duration.multipliedBy(scalar));
      }
docs: Returns an instance with the amount multiplied by the specified scalar.
  <p>
  This instance is immutable and unaffected by this method call.
  
  @param scalar  the scalar to multiply by, not null
  @return the amount multiplied by the specified scalar, not null
  @throws ArithmeticException if numeric overflow occurs