abstract class Animal {
    // 抽象方法：动物叫声
    public abstract void makeSound();
}

// 2. Swimmable 接口
interface Swimmable {
    // 游泳方法
    void swim();
}

// 3. Dog 类：继承 Animal，实现 Swimmable
class Dog extends Animal implements Swimmable {
    @Override
    public void makeSound() {
        System.out.println("小狗汪汪叫：汪汪汪！");
    }

    @Override
    public void swim() {
        System.out.println("小狗在水里狗刨式游泳！");
    }
}

// 4. Cat 类：继承 Animal，不实现 Swimmable
class Cat extends Animal {
    @Override
    public void makeSound() {
        System.out.println("小猫喵喵叫：喵喵喵！");
    }
}