I am currently learning Java and my first project is a simple calculator.
For some reason it does not accept decimal numbers that have “.” in them, but does accept “,”
I can use “0,4 + 0,4” but it won’t work with “0.4 + 0.4”

import java.util.Scanner;

class Operations {

public static void subtractTwoNumbers(double a, double b) {
    System.out.println(a - b);
}

public static void sumTwoNumbers(double a, double b) {
    System.out.println(a + b);
}

public static void divideTwoNumbers(double a, double b) {
    if (b == 0) {
        System.out.println("Error!");
    } else {
        System.out.println(a / b);
    }
}

public static void multiplyTwoNumbers(double a, double b) {
    System.out.println(a * b);
}

// Implemented method
public static void power(double n, double p) {
    long result = 1;
    while (p > 0) {
        if (p % 2 != 0) {
            result *= n;
        }
        p /= 2;
        n *= n;
    }
    System.out.println(result);
}

}

public class SimpleCalculator {
public static void main(String[] args) {

   Scanner scanner = new Scanner(System.in);

    System.out.println("Enter number 1: ");
    double num1 = scanner.nextDouble();

    System.out.println("Choose an operator n '+' n '-' n '*' n '/' n '^' ");
    String operator = scanner.next();

    System.out.println("Enter number 2: ");
    double num2 = scanner.nextDouble();

    switch (operator) {
        case "^":
            Operations.power(num1, num2);
            break;
        case "+":
            Operations.sumTwoNumbers(num1, num2);
            break;
        case "-":
            Operations.subtractTwoNumbers(num1, num2);
            break;
        case "/":
            Operations.divideTwoNumbers(num1, num2);
            break;
        case "*":
            Operations.multiplyTwoNumbers(num1, num2);
            break;
        default:
            System.out.println("You entered an invalid operator");
    }
    scanner.close();
}

}