题解 | #记负均正II#

DecimalFormat

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.text.DecimalFormat;

public class Main {
    public static void main(String args[]) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String str;
        int countNegative = 0;
        int countPositive = 0;
        int sum = 0;
        while ((str = reader.readLine()) != null) {
            Integer item = Integer.parseInt(str);
            if (item < 0) {
                countNegative++;
            } else {
                countPositive++;
                sum += item;
            }
        }
        System.out.println(countNegative);
        if (countPositive == 0) {
            System.out.println(0.0);
        } else {
            DecimalFormat df = new DecimalFormat(".#");
            System.out.println( df.format((double) sum / (double)countPositive));
        }
    }
}