39 编写一个函数，输入n为偶数时，调用函数求1/2+1/4+...+1/n,当输入n为奇数时，调用函数1/1+1/3+...+1/n(利用指针函数)

题目：编写一个函数，输入n为偶数时，调用函数求1/2+1/4+...+1/n,当输入n为奇数时，调用函数1/1+1/3+...+1/n(利用指针函数)

   public class _039PrintFunction {

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

    private static void printFunction() {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入一个正整数 :");
        int n = scanner.nextInt();

        System.out.println("相应数列的和为 :" + sum(n));
    }

    private static double sum(int n) {
        double res = 0;
        if (n % 2 == 0) {
            for (int i = 2; i <= n; i += 2) {
                res += (double) 1 / i;
            }
        } else {
            for (int i = 1; i <= n; i += 2) {
                res += (double) 1 / i;
            }
        }
        return res;
    }
}