Java 异常处理：禁止输入字母的代码示例

public class LetterInputException extends Exception {
    public LetterInputException(String message) {
        super(message);
    }
}

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        try {
            String input = scanner.nextLine();
            if (input.matches(".*[a-zA-Z]+.*")) {
                throw new LetterInputException('Input contains letters');
            }
            System.out.println('Input is valid: ' + input);
        } catch (LetterInputException e) {
            System.out.println('Error: ' + e.getMessage());
        }
    }
}