java - 在用户输入正确的格式后，如何使扫描仪可重复多次

Question

我正在尝试将货币的值(value)从美元转换为每种硬币的值(value)(以美分为单位)。我想让这段代码可重复，而不需要重新运行脚本。下面列出了我遇到的问题；

• 使此可重复性/改进我的代码的其他方法是什么
• 使用后键入第二个输入，而不是输出第一个输出的代码
• 第二次尝试后，捕获异常无效检查器将不起作用
• 如何使此代码可按以下格式重复

public class MakeChange {

    public static void main(String[] args) throws Exception {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter a dollar amount:");
        boolean isValidAmount = false;
        String amountInString = input.nextLine();
        double amount = 0;
        try {
            if (amountInString.isEmpty() || amountInString.equals(" ")) {
                System.out.println("INVALID");
            }
        } catch (InputMismatchException e) {
            e.printStackTrace();
        }

        if (amountInString.chars().allMatch(Character::isAlphabetic)) {
            System.out.println("INVALID");
        } else {
            amount = Double.parseDouble(amountInString);
            isValidAmount = true;
            convert(amount);
        }
        while (isValidAmount = true) {
            System.out.print("Enter a dollar amount:");
            amountInString = input.nextLine();
            convert(amount);
        }
    }

    private static void convert(double amount) {
        int toonies;
        int loonies;
        int quarters;
        int dimes;
        int nickels;
        int remainingCents;

        remainingCents = (int) (amount * 100 + .5);
        toonies = remainingCents / 200;
        remainingCents %= 200;
        loonies = remainingCents / 100;
        remainingCents %= 100;
        quarters = remainingCents / 25;
        remainingCents %= 25;
        dimes = remainingCents / 10;
        remainingCents %= 10;
        nickels = remainingCents / 5;
        remainingCents %= 5;

        System.out.println("toonies:" + toonies + ";" + " loonies:" + loonies + ";" + " quarters:" + quarters + ";"
                + " dimes:" + dimes + ";" + " nickels:" + nickels);

    }
}

(预期格式示例)

输入美元金额:12 图尼:6；加元:0；宿舍:0；一毛钱:0；镍币:0 输入美元金额:42 图尼:10；加元:0；宿舍:2；一毛钱:0；镍币:0 (当前问题) 输入美元金额:12 图尼:6；加元:0；宿舍:0；一毛钱:0；镍币:0 输入美元金额:42' 图尼:6；加元:0；宿舍:0；一毛钱:0；镍币:0

Answer 1

您可以将 boolean 值更改为 isValidAmount 方法:

private static boolean isValidAmount(String input) {

      if (input.isEmpty() || input.equals(" ")) {
        System.out.println("INVALID input:" + input);
        return false;
      }

    if (input.chars().allMatch(Character::isAlphabetic)) {
      System.out.println("INVALID input: " + input );
      return false;
    } else {
      return true;
    }
  }

然后您可以将 boolean 值 isValid 移至 while 循环:

public static void main(String[] args) throws Exception {
    Scanner input = new Scanner(System.in);
    System.out.print("Enter a dollar amount:");
    String amountInString;

    while ((amountInString = input.nextLine()) != null && isValidAmount(amountInString)) {
      // remove the  System.out.print("Enter a dollar amount:"); from the while loop
      double amount = Double.parseDouble(amountInString);
      convert(amount);
    }
  }

这样每次迭代都会刷新 isValidAmount boolean 值。

出于格式化目的，将 System.out.print("Enter adollar amount:"); 放在 convert 方法中，而不是 while 循环中。

private static void convert(double amount) {
        int toonies;
        int loonies;
        int quarters;
        int dimes;
        int nickels;
        int remainingCents;

        remainingCents = (int) (amount * 100 + .5);
        toonies = remainingCents / 200;
        remainingCents %= 200;
        loonies = remainingCents / 100;
        remainingCents %= 100;
        quarters = remainingCents / 25;
        remainingCents %= 25;
        dimes = remainingCents / 10;
        remainingCents %= 10;
        nickels = remainingCents / 5;
        remainingCents %= 5;

        System.out.println("toonies:" + toonies + ";" + " loonies:" + loonies + ";" + " quarters:" + quarters + ";"
                + " dimes:" + dimes + ";" + " nickels:" + nickels + ";" + " remainingCents:" + remainingCents);
        System.out.print("Enter a dollar amount:");

    }

几行的输出现在将是:

输入美元金额:26.50 图尼:13；加元:0；宿舍:2；一毛钱:0；镍币:0；剩余分:0 输入美元金额:2315.90 图尼:1157；加元:1；宿舍:3；一毛钱:1；镍币:1；剩余分:0 输入美元金额:1222 图尼:611；加元:0；宿舍:0；一毛钱:0；镍币:0；剩余分:0 输入美元金额:0.05 卡通:0;加元:0；宿舍:0；一毛钱:0；镍币:1；剩余分:0 输入美元金额:0.01 卡通:0;加元:0；宿舍:0；一毛钱:0；镍币:0；剩余美分:1