加泰罗尼亚数字程序的Java循环问题

Question

我正在尝试编写一个程序，它从用户那里获取一个整数值(n)，然后调用我的catalan numbers方法并找到第n个值。它除了两个错误之外都工作；首先，当我输入'quit‘时，它给出错误消息'Exception in thread "main“java.lang.NumberFormatException: For input string："quit"’。

下面是我的代码：

public class Exercise_3 {
    public static long catalan(int n) throws IllegalArgumentException {

        int res = 0;

        // Base case
        if (n <= 1) {
            return 1;


        }

        for (int i = 0; i < n; i++) {
            res += catalan(i) * catalan(n - i - 1);

        }
        return res;

    }

    public static void exercise3a() {
        Scanner scan = new Scanner(System.in);

        System.out.println("Please enter an integer greater than 0 and less than 30 or type 'quit' to exit :");

        String input = scan.next();
        int number = Integer.parseInt(input);

        if (input.equals("quit")) {
                System.out.println("quitting");
        }

        while (!input.equals("quit")){
                int i = (int) catalan(number);
                System.out.println(i);
                System.out.println("Please enter an integer greater than 0 and less than 30 or type 'quit' to exit :");
                String continued;
            continued = scan.next();
            int continue_loop = Integer.parseInt(continued);
                int f = (int) catalan(continue_loop);
                System.out.println(f);
            }

        }

    public static void main(String[] args) {
        exercise3a();
    }
}

任何帮助都将不胜感激。

Answer 1

问题就在这里

   String input = scan.next();
    int number = Integer.parseInt(input);

    if (input.equals("quit")) {
            System.out.println("quitting");
    }