public class Main {
    public static void main(String[] args) {
        // Test polymorphism with Animal references
        Animal dog = new Dog();
        Animal cat = new Cat();

        System.out.println("Testing makeSound():");
        dog.makeSound(); // Should output "Woof!"
        cat.makeSound(); // Should output "Meow!"

        // Test swim() method for Dog
        System.out.println("\nTesting swim():");
        if (dog instanceof Swimmable) {
            Swimmable swimmableDog = (Swimmable) dog;
            swimmableDog.swim(); // Should output "Dog is swimming"
        }

        // Test that Cat doesn't implement Swimmable
        if (!(cat instanceof Swimmable)) {
            System.out.println("Cat cannot swim");
        }
    }
}