I can't figure out how to add taxes

Question

I can't figure out how to add the taxes to the berry banana price. Would I need to use math.pow or is there a specific way to add fraction results to an decimal number? Probably such a silly question but I can't figure out it, my teacher wants me to use constants for everything. Please let me know if there's multiple ways to do this.

public static void main(String[] args) {
    // TODO Auto-generated method stub

    final double BERRY_BANANA_PRICE = 7.50;
    final double TROPICAL_PRICE = 6.75;
    final double GREEN_JOLT_PRICE = 5.00;
    final double TAX_RATE = 8.25 / 100;
    final double ADD_IN_PRICE = 1.50;

    Scanner input = new Scanner(System.in);

    System.out.println("CS1150 Beach Smoothie Bar!");
    System.out.println("");
    System.out.println("Option   Type           Price");
    System.out.println("------------------------------------");
    System.out.printf("1        Berry Banana   $%.2f\n", + BERRY_BANANA_PRICE);
    System.out.printf("2        Tropical    $%.2f\n", + TROPICAL_PRICE);
    System.out.printf("3        Green Jolt  $%.2f\n", + GREEN_JOLT_PRICE);

    System.out.println("");

    System.out.print("Select a smoothie: 1, 2, or 3:");
    int selectasmoothie = input.nextInt();

    System.out.println("");

    if (selectasmoothie >= 1 && selectasmoothie <= 3) {

        System.out.println("Option   Add-In              Price");
        System.out.println("----------------------------------");
        System.out.println("0        No add-in       $0.00");
        System.out.printf("1        Almond Butter       $%.2f\n", + ADD_IN_PRICE);
        System.out.printf("2        Lime juice       $%.2f\n", + ADD_IN_PRICE);

        System.out.println("");

        System.out.print("Select an add-in: ");
        int selectanaddin = input.nextInt();
        if (selectanaddin >= 0 && selectanaddin <= 1) {

            System.out.println("");
            System.out.println("------------------------------");
            System.out.printf("Berry Banana Smoothie  $%.2f\n", BERRY_BANANA_PRICE);
            System.out.println("");
            System.out.printf("Taxes                  $%.2f\n", BERRY_BANANA_PRICE * TAX_RATE);
            System.out.println("------------------------------");
            System.out.printf("Total Cost             $%.2f\n",BERRY_BANANA_PRICE +  );
        } else {
            System.out
                    .printf(selectanaddin + " " + "is not a valid menu item. Please run program again, good bye!");
        }
    }
}// main

Answer 1

1. Separate your business logic from you view logic (calculate all your variable and just print them later), it will make your code easier to read and maintain.

2. You have 3 kinds of smoothies (plus add-ins), save the value of the smoothie (plus add-ins) in a variable called totalPrice.

3. System.out.printf("1 Berry Banana $%.2f\n", + BERRY_BANANA_PRICE); will not compile, you need a variable before the +. The same mistake is in several lines (probably just a copy and paste error).

4. To increase an amount by a percentage use value * (1 + percentage) (- if you want to decrease it, like making a discount).

5. It is not advisable to use floating points to represent money because it can introduce rounding errors, use BigDecimal instead.