如果用户输入错误，如何保持继续同一行？

Question

当我运行代码时，如果你输入字符而不是整数，它会提示再次重新输入。 但是当我们回答第 2 或第 3 个问题时，如果错了，它会要求您回到第 1 个问题。 有什么办法可以解决吗？ 非常感谢！

 while (true) {
       try {
           Scanner input = new Scanner(System.in);

           System.out.println("Enter your monthly income (after tax and insurance): ");
           float monthlyIncome = input.nextFloat();

           System.out.println("Enter monthly cost for food: ");
           float monthlyFoods = input.nextFloat();

           System.out.println("Enter monthly cost for rent: ");
           float monthlyRent = input.nextFloat();

           System.out.println("Enter monthly cost for utilities " +
                   "(e.g. gas, phone bills, Internet): ");
           float monthlyUtilities = input.nextFloat();

           System.out.println("Enter monthly cost for shopping and hobbies: ");
           float monthlyHobbies = input.nextFloat();

           System.out.println("Do you plan for saving? (Enter 0 if not): ");
           float monthlySaving = input.nextFloat();

           monthlyExpenses(monthlyIncome, monthlyFoods, monthlyRent, 
                   monthlyUtilities, monthlyHobbies, monthlySaving);
           break;

    } catch (InputMismatchException exception) {
        System.out.println("Please enter number only!");
    }
  }

Answer 1

  public static float getFloat(String message)
  {
   float value;
   while (true) {
   try {
       Scanner input = new Scanner(System.in);
       System.out.println(message);
       value=input.nextFloat();

  } catch (InputMismatchException exception) {
    System.out.println("Please enter number only!");
  }}
  return value;
  }
    float monthlyIncome = getFloat("Enter your monthly income (after tax and insurance): ");

//类似这样的

Answer 2

使用您需要重复的代码，以防 while 循环中出现错误； 这使您的代码看起来像这样：

while (true) {
    float value;
    try {
    // code to get proper value from user & store in `value`     
    return value;
    } catch (InputMismatchException exception) {
        System.out.println("Please enter number only!");
    }
  }

现在只需将此代码移动到一个方法：

float getFloatValue(String questionDescription){

while (true) {
    float value;
    try {
      Scanner input = new Scanner(System.in); 
      System.out.println(questionDescription+": ");
      value = input.nextFloat();
      return value;
    } catch (InputMismatchException exception) {
        System.out.println("Please enter number only!");
    }
  }
 return Float.NaN;
}

所以最后获取值的代码如下所示：

          float monthlyIncome = getFloatValue("Enter your monthly income (after tax and insurance)");

          float monthlyFoods = getFloatValue("Enter monthly cost for food");

          float monthlyRent = getFloatValue("Enter monthly cost for food");
          // get other values same as above
           monthlyExpenses(monthlyIncome, monthlyFoods, monthlyRent, 
                   monthlyUtilities, monthlyHobbies, monthlySaving);

这种方法的好处是只接受有效的浮点值，并且您的代码看起来也很干净。

Answer 3

另一种可能性是将所有问题保存到一个数组中，并使用一个变量作为索引来计算传递了多少输入。 然后在第二个数组中保存输入，最后你只需要转换它。

优点：这是高度可定制的，可以很容易地扩展。

代码看起来像那样。

// Lots of Code here
Scanner scan = new Scanner(System.in);
int count = 0;
String[] questions = {"How high...?", "[Insert questions 2]"}; // Put in all your questions here
float[] answers = new float[questions.length]; // array for answers
while(count < questions.length) {
    try {
        System.out.println(questions[count]);
        answers[count] = Float.parseFloat(scan.nextLine());
        count++;
    } catch (Exception e) {
        System.out.println("Bad doggo! No food for you tonight!"); // Tell the user he was a bad guy
    }
}
scan.close();
// If you want you can convert the answer array back to variables here but I think this way is easier
// More code