39 编写一个函数，输入n为偶数时，调用函数求1/2+1/4+

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)

 1    public class _039PrintFunction {
 2 
 3     public static void main(String[] args) {
 4         printFunction();
 5     }
 6 
 7     private static void printFunction() {
 8         Scanner scanner = new Scanner(System.in);
 9         System.out.println("请输入一个正整数 :");
10         int n = scanner.nextInt();
11 
12         System.out.println("相应数列的和为 :" + sum(n));
13     }
14 
15     private static double sum(int n) {
16         double res = 0;
17         if (n % 2 == 0) {
18             for (int i = 2; i <= n; i += 2) {
19                 res += (double) 1 / i;
20             }
21         } else {
22             for (int i = 1; i <= n; i += 2) {
23                 res += (double) 1 / i;
24             }
25         }
26         return res;
27     }
28 }