Java 输入不匹配异常错误。我该如何解决这个问题？

Question

仅当我输入 10 个或更多 3 和 7 的数字时才会出现。就是来自下面这个方法，我测试了一下没有这个方法。这是代码

Scanner input = new Scanner(System.in);
    System.out.print("Enter a positive integer...");
    int num = input.nextInt();

    // Outputs
    System.out.println("Number of digits in number is " + numberDigits(num));
    System.out.println("Number begins with " + firstNum(num));
    System.out.println("Number ends with " + lastNum(num));
    System.out.println("Does number begin with 7? " + beginWith(num, 7));
    System.out.println("Does number begin with 3? " + beginWith(num, 3));
    System.out.println("Does number contain a 7? " + contains(num, 7));
    System.out.println("Does number contain a 3? " + contains(num, 3));
    System.out.println("Is the number divisible by 13? " + divTest(num, 13));
    System.out.println("Is the number divisible by 77? " + divTest(num, 77)); 
    System.out.println("How many times does 7 appear in the number? " + digitAppearances(num, 7));
    System.out.println("How many times does 3 appear in the number? " + digitAppearances(num, 3));

public static int digitAppearances(int num, int x) {

    // Check if num is 0
  if (num <= 0 ) {
    return 0;
  }

// Count number of times x appears
else if (num % 10 == x) {
    return 1 + digitAppearances(num / 10, x);
}
else {
    return digitAppearances(num / 10, x);
}
}

Answer 1

扫描仪正在尝试读取 the nextInt method 的 int .

An invocation of this method of the form nextInt() behaves in exactly the same way as the invocation nextInt(radix), where radix is the default radix of this scanner.

• nextInt(基数):

Throws:

InputMismatchException - if the next token does not match the Integer regular expression, or is out of range

如果您输入的值大于 Integer.MAX_VALUE(大约 21 亿，10 位数字)，那么您将收到 InputMismatchException。

如果您想输入最多 19 位数字，请使用 nextLong。

如果你想输入任意数量的数字，只需调用next，获取字符串，并验证它是否只包含数字。在进一步处理之前，您需要将字符数字转换为数字类型。