Compute deviation

The problem

Programming exercise computes the standard deviation of numbers. This exercise uses a different but equivalent formula to compute the standard deviation of n numbers. To compute the standard deviation with this formula, you have to store the individual numbers using an array, so that they can be used after the mean is obtained. Your program should contain the following methods:

public static double deviation(double[] x)
public static double mean(double[] x)

Breaking it down

static final int USER_INPUT_SIZE = 10;

public static void main(String[] args) {

    Scanner input = new Scanner(System.in);
    double[] numbers = new double[USER_INPUT_SIZE];
    System.out.print("Enter " + USER_INPUT_SIZE + " numbers: ");
    for (int i = 0; i < numbers.length; i++) {
        numbers[i] = input.nextDouble();
    }

    input.close();

    System.out.println("The mean is: " + mean(numbers).getAsDouble());
    System.out.println("The standard deviation is: " + deviation(numbers));

}

public static double deviation(double[] x) {

    double mean = mean(x).getAsDouble();
    double deviation = 0;
    for (int i = 0; i < x.length; i++) {
        deviation += Math.pow(x[i] - mean, 2);
    }
    return Math.sqrt(deviation / (x.length - 1));
}

public static OptionalDouble mean(double[] x) {

    return Arrays.stream(x).average();
}

Output

Enter 10 numbers: 2
886
44
33
66
88
99
55
22
22
The mean is: 131.7
The standard deviation is: 266.7645861887301