StandardDeviation

import java.util.Arrays;
import java.util.Scanner;

public class StandartDeviation {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        //First we enter the number of players and check if the input is correct.
        System.out.println("Enter number of players: ");
        String number = scanner.nextLine();
        while (!number.matches("\\d+")) {
            System.out.println("Number must be integer. Try again.");
            number = scanner.nextLine();
        }
        int n = Integer.parseInt(number);
        //Then we create the score array and check it.
        double[] scores = new double[n];
        boolean isDigit = true;
        System.out.println("Enter scores separated by ','");
        String[] scoresLine = scanner.nextLine().split(",".trim());
        for (int i = 0; i < n; i++) {
            if (!scoresLine[i].matches("\\d+")) {
                System.out.printf("The score %d is entered incorrectly.%n", i + 1);
                isDigit = false;
                break;
            } else scores[i] = Double.parseDouble(scoresLine[i]);
        }
        //Check if scores was given correctly.
        while (n != scores.length || n != scoresLine.length || !isDigit) {
            System.out.println("Your input is wrong. Try again.");
            scoresLine = scanner.nextLine().split(",".trim());
        }

        System.out.printf("The fastest is %.2f%nThe slowest is %.2f%nThe average is %.2f%nThe standard deviation is %.2f%n",
                theFastest(scores), theSlowest(scores), average(scores), standardDeviation(scores));

    }

    public static double theFastest(double[] arr) {
        double fastest = arr[0];
        for (int i = 0; i < arr.length; i++) {
            if (arr[i] > fastest) {
                fastest = arr[i];
            }
        }
        return fastest;
    }

    public static double theSlowest(double[] arr) {
        double slowest = arr[arr.length - 1];
        for (int i = 0; i < arr.length; i++) {
            if (arr[i] < slowest) {
                slowest = arr[i];
            }
        }
        return slowest;
    }

    public static double average(double[] arr) {
        double sum = 0;
        double average = 1;
        for (int i = 0; i < arr.length; i++) {
            sum += arr[i];
            average = sum / arr.length;
        }
        return average;
    }

    public static double standardDeviation(double[] arr) {
        double sd1 = 0;
        double sd = 0;
        for (int i = 0; i < arr.length; i++) {
            sd1 += Math.pow(arr[i] - average(arr), 2);
            sd = Math.sqrt(sd1 / arr.length);
        }
        return sd;
    }
}