Java 递归中出现的问题

递归打印数字的每一位（按顺序打印一个数字的每一位(例如 1234 打印出 1 2 3 4)    （递归））

public static void print(int n) {
        if(n < 10) {
            System.out.println(n);
        }else {
            print(n / 10);
            System.out.println(n % 10);
        }
    }

    public static void main5(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        print(n);
    }

 

 递归求解汉诺塔问题

public static void move(char pos1,char pos2) {
        System.out.println(pos1+" -> "+pos2+" ");
    }

    public static void hanoi(int n,char pos1,char pos2,char pos3) {
        if(n == 1) {
            move(pos1,pos3);
        }else {
            hanoi(n - 1,pos1,pos3,pos2);
            move(pos1,pos3);
            hanoi(n - 1,pos2,pos1,pos3);
        }
    }

    public static void main7(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        hanoi(n, 'A', 'B', 'C');
    }

    //6、递归求斐波那契数列的第 n 项
    public static int fib2(int n) {
        if(n == 1 || n == 2) {
            return 1;
        }
        return fib2(n-1) + fib2(n-2);
    }

    public static void main6(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        System.out.println(fib2(n));
    }

返回的数字之和（写一个递归方法，输入一个非负整数，返回组成它的数字之和） 

public static int fun(int n) {
        if(n < 10) {
            return n;
        }
        return n % 10 + fun(n / 10);
    }
    
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        System.out.println(fun(n));
    }