Solution with some bugs:

import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.println("Enter array length from 1 to 100: ");

        if (input.hasNextInt()) {
            int arrLength = input.nextInt();

            if (arrLength > 100) {
                System.out.println("Enter array length from 1 to 100: ");
            } else {
                // fill numbers [-50.00; 50.00])
                double[] arr = new double[arrLength];

                Random random = new Random();

                double a = -50.00;
                double b = 50.00;

                for (int i = 0; i  0) {
                        double sum = 0;
                        for (int j = 0; j < arr.length; j++) {
                            sum += arr[j];
                        }
                        average = sum / arr.length;
                        System.out.println("Avarage: " + average);
                    }
                }
            }
        }
    }
}

part of code solution:
arrays