public static void main(String[]args){
        AnimalFactory animalFactory = AnimalFactory.getAnimalFactoryInstance();
        
        Animal a1 = animalFactory.getAnimal("feline");
        System.out.println("a1 sound: " + a1.makeSound());
        
        Animal a2 = animalFactory.getAnimal("canine");
        System.out.println("a2 sound: " + a2.makeSound());
    }