java/w6/MainSix.java

public class MainSix {
    public static abstract class Animal {
        protected String name;

        Animal(String name) {
            this.name = name;
        }

        abstract public void makeSound();
    }

    public interface Swimmable {
        void swim();
    }

    public static class Dog extends Animal implements Swimmable {
        Dog(String name) {
            super(name);
        }

        @Override
        public void makeSound() {
            System.out.printf("This is dog %s.%n", this.name);
        }

        @Override
        public void swim() {
            System.out.printf("Dog %s swimming.%n", this.name);
        }
    }

    public static class Cat extends Animal {
        Cat(String name) {
            super(name);
        }

        @Override
        public void makeSound() {
            System.out.printf("This is cat %s.%n", this.name);
        }
    }

    public static void trySwim(Animal animal) {
        System.out.printf("Moving %s to swimming pool.%n", animal.name);

        if (animal instanceof Swimmable) {
            ((Swimmable) animal).swim();
        } else {
            System.out.printf("Oops, looks like %s cannot swim...%n", animal.name);
        }
    }

    public static void main(String[] args) {
        Animal dog1 = new Dog("Adam");
        Animal dog2 = new Dog("Belly");
        Animal cat1 = new Cat("Carl");

        dog1.makeSound();
        dog2.makeSound();
        cat1.makeSound();

        trySwim(dog1);
        trySwim(dog2);
        trySwim(cat1);
    }
}