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;
     }
 }