通过if语句调用方法时，出现NoSuchElementException

Question

试图制作一个程序来测试用户的算术技能。 level1方法会生成两个不超过10的随机数，然后测试用户的答案。当在if语句中调用level1方法时，它可以完美运行，但是在线程“ main”中抛出NoSuchElementException，如何避免这种情况？

public static void main(String[] args) {

        if (level1() == true) {
            System.out.println("passed level 1");
            } else { System.out.println("failed level 1");
            }

        if (level2() == true) {
                System.out.println("passed level 2");
                }else {
            System.out.println("failed level 2");
        }

    }


    public static boolean level1() {
        boolean passFail;

        Scanner in = new Scanner(System.in); 
        Random ran = new Random();
        int indexNum;

        int num1 = ran.nextInt(10);
        indexNum = 10 - num1;
        int num2 = ran.nextInt(indexNum);

        int sum = num1 + num2;

        System.out.println("Level 1:");
        System.out.println("What is " + num1 + " + " + num2);

        if(sum == Integer.parseInt(in.next())) {
            System.out.println("Correct!");
            passFail = true;

        } else {
        System.out.println("Incorrect");
        passFail = false;
        } 
        in.close();
        return passFail;
}