import java.util.ArrayList;

public class Variance {

    public static int sum(ArrayList<Integer> list) {
        int sum = 0;

        for (int number : list) {
            sum += number;
        }
        return sum;
    }

    public static double average(ArrayList<Integer> list) {
        int sum = sum(list);
        double average = (double) sum / list.size();

        return average;
    }

    public static double variance(ArrayList<Integer> list) {
        int sum = sum(list);
        double average = average(list);

        int sumSquared = sum * sum;
        int firstNumber = sumSquared / list.size();
        int numberSquared = 0;

        for (int number : list) {
            number *= number;
            numberSquared += number;
        }
        int secondNumber = numberSquared - firstNumber;

        double variance = (double) secondNumber / list.size() - 1;

        return variance;
    }

    public static void main(String[] args) {
        ArrayList<Integer> list = new ArrayList<Integer>();
        list.add(3);
        list.add(2);
        list.add(7);
        list.add(2);

        System.out.println("The variance is: " + variance(list));
    }
}