Below and Above Average [first one]

public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String[] str = scanner.nextLine().split(",");
        int[] nums = new int[str.length];
        for (int i = 0; i < str.length; i++) {
            nums[i] = Integer.parseInt(str[i]);
        }
        StringBuilder below = new StringBuilder();
        StringBuilder above = new StringBuilder();
        double avg = 0.0;

        for (int i = 0; i < nums.length; i++) {
            if (nums[i] <= 0 && i != nums[nums.length - 1]) {
                if (below.length() == 0) {
                    below.append(nums[i]);
                } else {
                    below.append(",").append(nums[i]);
                }
            }
        }
        for (int i = 0; i < nums.length; i++) {
        if (nums[i]>0 && i!=nums[nums.length-1]){
            if (above.length()==0){
                above.append(nums[i]);
            } else {
                above.append(",").append(nums[i]);
            }
        }
        }
        for (int num : nums) {
            avg += num;
        }
        System.out.printf("avg: %.2f%n",avg/nums.length);
        System.out.printf("below: %s%n", below);
        System.out.printf("above: %s%n", above);
    }
}