

            // retrieve textual input parameters
            String purchaseDate = request.getParameter("purchaseDate");
            String creditCard = request.getParameter("creditCard");
            
            // retrieve numeric input parameters and convert type
            String s = request.getParameter("purchasePrice");
            double price = Double.parseDouble(s);
            
            s = request.getParameter("gallons");
            double gallons = Double.parseDouble(s);

            s = request.getParameter("milesDriven");
            double milesDriven = Double.parseDouble(s);
            
            // retrieve checkbox items
            String discounted = request.getParameter("discounted");
            
            // create a GasPurchase and initialize it
            GasPurchase gp = new GasPurchase();
            gp.setCreditCard(creditCard);
            if (discounted == null)
                gp.setDiscounted(false);
            else
                gp.setDiscounted(true);
            gp.setGallons(gallons);
            gp.setMilesDriven(milesDriven);
            gp.setPurchaseDate(purchaseDate);
            gp.setPurchasePrice(price);
            
            // add the purchase to the list
            purchases.addPurchase(gp);            
