public static boolean getChoice () {
		String message = "";
		boolean chosen = false;
		Scanner sc = new Scanner (System.in);
		boolean inputOK = false;
		while (! inputOK) {
			String choice = sc.nextLine();
			choice = choice.toUpperCase();
			if (choice != null) {
				if ( choice.equals("Y") || choice.equals("N")) {
					inputOK = true;
					if (choice.equals("Y")) {
						chosen = true;
					} 
				} else {
					message = "ongeldige ingave (Y/y of N/n)";
				}
			} else {
				message = "niets ingegeven";
			}
			if (! message.isEmpty()) {
				System.out.println(message);
			}
		}
		return chosen;
	}