java - 带迭代的 While 循环

Question

我正在尝试创建一个 while 循环，其中用户总共尝试输入有效数字三次。我不明白系统如何识别在显示消息之前已经进行了 3 次无效尝试。 创建类、变量和扫描仪对象。经过三次尝试后，我想说“不再尝试”。我已经编写了程序，以使用用户输入的数量(如果有效)。这仅适用于他们输入三个无效尝试的情况。

Updated code: 

整数数量 = 0;

        // Get user's desired amount of lemonade cups
        System.out.print("Hello " + name + ". How many cups of lemonade can I get you? ");
        quantity = keyboard.nextInt(); // Store amount of cups wanted

        int attempts = 0;
        int maxAttempts = 3;
        double subTotal = quantity * lemonadeCost;
        double totalTax = subTotal * 0.08;
        double totalPrice = subTotal + totalTax;

        while (attempts < maxAttempts) {
            if (quantity < 1 || quantity >= 20) {
                System.out.println("That is an invalid amount, please try again");
                quantity = keyboard.nextInt(); }

             else {
                 System.out.println("Subtotal: " + defaultFormat.format(subTotal));
                 System.out.println("Tax: " + defaultFormat.format(totalTax));
                 System.out.println("Total: " + defaultFormat.format(totalPrice)); 

            }
             attempts++;
                if (attempts >= 3) {
                    System.out.print ("No lemonade for you");
                    break;
                }
            // Ask for user's payment method
            Scanner method = new Scanner(System.in);
            System.out.println("How would you like to pay? Enter 'm'   for money, 'c' for credit or 'g' for gold. ");
            String payment = method.nextLine(); 

Answer 1

dxdy关于创建 while() 循环函数所需的大括号，正确的是。

一旦 while 循环结束(数量在 1 到 20 之间，或者尝试次数 > maxAttempts)，您只需要一个如下的 if 语句:

if (attempts > maxAttempts) {
  System.out.println("No more tries);
  return -1; // or something else to break out of your code
}

然后继续使用数量变量的其余代码。