code: private double getLogDiscountFactorForDiscounting(double time) {
  		return discountCurveForDiscountRate == null ? -discountRate * time : Math.log(discountCurveForDiscountRate.getDiscountFactor(null, time));
  	}
docs: Small helper to calculate rate off the curve or use constant.
  
  @param time Maturity.
  @return The log of the discount factor, i.e., - rate * time.