public static void main(String[] args) {
        Zoo aZoo = new Zoo();
        ZooInterface aZooInterface = new ZooInterface();
        Scanner userInput = new Scanner(System.in);
        String user_input;

        do {
            aZooInterface.displayOptions();
            user_input = userInput.nextLine();

            if (user_input.equals("1")) {
                Pen penToAdd = aZooInterface.addPen();
                aZoo.addPenToZoo(penToAdd);
            } else if (user_input.equals("2")) {
                String nameToDelete = aZooInterface.userPenName();
                Pen penToDelete = aZoo.searchPenByName(nameToDelete);
                aZoo.deletePenFromZoo(penToDelete);
            } else if (user_input.equals("3")) {

            } else if (user_input.equals("4")) {

            } else if (user_input.equals("5")) {

            } else if (user_input.equals("6")) {
                String searchPen = aZooInterface.userPenName();
                aZoo.searchPenByName(searchPen);
                aZoo.penInfoDisplay();
                // get it to display only the pen I search for
            } else if (user_input.equals("7")) {

            } else if (user_input.equals("8")) {
                System.out.println("You are now exiting the program. Thank you!");
            } else {
                System.out.println("Please select from options 1-8.");
            }
        } while(!user_input.equals("8"));
    }