java - 使用嵌套 if 语句进行计算

Question

我正在开发一个嵌套的程序，如果我的数学是正确的，唯一的事情是正确的输出没有打印。我不知道应该将输出行放在第一个 if、嵌套 if 或两行中的哪里？我测试的价格是一瓶进口香水，价格为 27.99。输出应该是 32.19，我得到的是 34.99。

public class SalesTax 
    {
    public static void main(String[] args) 
    {
        // Input items for shopping cart
        HashMap<String, String> cart = new HashMap<String, String>();
        HashMap<String, String> shoppingcart = new HashMap<String, String>();

        // Create a Scanner
        Scanner input = new Scanner(System.in);

        // variables
        char done;

        //boolean goods;
        double totalprice = 0.00;
        double taxprice;
        double ftax;

        // Pick items for list.
        do 
        {  
            System.out.print("Please enter an item.");
            String item = input.nextLine();

            System.out.print("Please enter the price for "+ item + ": ");
            String price = input.nextLine(); 

            double price1 = Double.parseDouble(price);
            totalprice += price1; 

            //System.out.println(String.format("%.2f",totalprice));
            String price2 = String.valueOf(price1);
            cart.put(item, price2);

            //determine if item will have additional tax
            if (item.contains("music"))
            {
                 price1 = Double.parseDouble(price);
                taxprice = price1 * .10;

                totalprice = (totalprice + taxprice);

                if (item.contains("imported"))
                {
                     price1 = Double.parseDouble(price);
                    ftax = price1 * .05;

                    totalprice = (totalprice + taxprice + ftax);
                }

                //System.out.println(String.format("%.2f",totalprice));
                String newprice2 = String.valueOf(String.format("%.2f", totalprice));
                shoppingcart.put(item,newprice2);
            }
            else if(item.contains("bottle"))
            {
                 price1 = Double.parseDouble(price);
                taxprice = price1 * .10;

                totalprice = (price1 + taxprice);

                if (item.contains("imported"))
                {
                     price1 = Double.parseDouble(price);
                    ftax = price1 * .05;

                    totalprice = (totalprice + taxprice + ftax);
                }

                //System.out.println(String.format("%.2f",totalprice));
                String newprice2 = String.valueOf(String.format("%.2f", totalprice));
                shoppingcart.put(item,newprice2);
            }
            else if (item.contains("imported"))
            {
                 price1 = Double.parseDouble(price);
                taxprice = price1 * .05;

                totalprice = (totalprice + taxprice);

                if (item.contains("imported"))
                {
                     price1 = Double.parseDouble(price);
                    ftax = price1 * .05;

                    totalprice = (totalprice + taxprice + ftax);
                }

                //System.out.println(String.format("%.2f",totalprice));
                String newprice2 = String.valueOf(String.format("%.2f", totalprice));
                shoppingcart.put(item,newprice2);
            }
            else 
            {
                shoppingcart.put(item, price);
            }


            System.out.print("Would you like to continue to add items? (Type Y) for Yes and (Type N) for No.");
            done = input.nextLine().charAt(0);
        } while(Character.toUpperCase(done) == 'Y');

       System.out.println("Your cart contains the following at items with tax" + shoppingcart); //+ String.format("%.2f", totalprice));
       System.out.println(String.format("%.2f",totalprice));
    }
}

Answer 1

尝试使用bigDecimal而不是float或double。

事实上，如果你尝试这样做:

double value = 10*0.09;
System.out.println(value);

你有:

0.8999999999999999

使用此方法:

BigDecimal value1 = new BigDecimal("10");
BigDecimal value2 = new BigDecimal("0.09");
BigDecimal value = value1.multiply(value2);
System.out.println(value);