两个计数器来记录正数和负数的个数,最后保留11位小数。

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] a = new int[n];
        for (int i = 0; i < n; i++) {
            a[i] = in.nextInt();
        }
        double sum = 0.0;
        int cnt1 = 0;
        int cnt2 = 0;
        for (int i : a) {
            if (i < 0)cnt1++;
            if (i > 0) {
                sum += i;
                cnt2++;
            }
        }
        double avg = 0.0;
        if (cnt2 == 0) {
            avg = 0;
        } else {
            avg = sum / cnt2;
        }
        System.out.printf("%d %.11f", cnt1, avg);
    }
}