// 抽象类 Animal
abstract class Animal {
    // 抽象方法：发出声音
    public abstract void makeSound();
}

// 接口 Swimmable
interface Swimmable {
    // 游泳方法
    void swim();
}

// Dog 类继承 Animal 并实现 Swimmable 接口
class Dog extends Animal implements Swimmable {
    @Override
    public void makeSound() {
        System.out.println("汪汪汪");
    }

    @Override
    public void swim() {
        System.out.println("小狗在游泳");
    }
}

// Cat 类仅继承 Animal
class Cat extends Animal {
    @Override
    public void makeSound() {
        System.out.println("喵喵喵");
    }
}

// 测试类
public class AnimalSoundSystem {
    public static void main(String[] args) {
        // 多态调用：Animal 类型引用子类对象
        Animal dog = new Dog();
        Animal cat = new Cat();

        System.out.println("=== 动物叫声测试 ===");
        dog.makeSound();
        cat.makeSound();

        System.out.println("\n=== 游泳能力测试 ===");
        // 向下转型：只有 Dog 实现了 Swimmable，才能调用 swim()
        if (dog instanceof Swimmable) {
            ((Swimmable) dog).swim();
        }
        if (cat instanceof Swimmable) {
            ((Swimmable) cat).swim();
        } else {
            System.out.println("猫不会游泳");
        }
    }
}