java/w6/AnimalSystem.java

// 抽象类 Animal
abstract class Animal {
    public abstract void makeSound();
}

// 接口 Swimmable
interface Swimmable {
    void swim();
}

// Dog 类继承 Animal 并实现 Swimmable
class Dog extends Animal implements Swimmable {
    @Override
    public void makeSound() {
        System.out.println("狗叫：汪汪汪！");
    }
    
    @Override
    public void swim() {
        System.out.println("狗会游泳，正在狗刨式前进...");
    }
}

// Cat 类继承 Animal，不实现 Swimmable
class Cat extends Animal {
    @Override
    public void makeSound() {
        System.out.println("猫叫：喵喵喵～");
    }
}

// 测试主类
public class AnimalSystem {
    public static void main(String[] args) {
        // 多态调用：父类引用指向子类对象
        Animal dog = new Dog();
        Animal cat = new Cat();
        
        System.out.println("===== 动物叫声系统 =====");
        dog.makeSound();
        cat.makeSound();
        
        System.out.println("\n===== 游泳测试 =====");
        // Dog 实现了 Swimmable，可以调用 swim()
        if (dog instanceof Swimmable) {
            ((Swimmable) dog).swim();
        }
        
        // Cat 没有实现 Swimmable，不能调用 swim()
        if (cat instanceof Swimmable) {
            ((Swimmable) cat).swim();
        } else {
            System.out.println("猫不会游泳，所以不能调用 swim() 方法");
        }
        
        System.out.println("\n===== 完整多态演示 =====");
        // 使用 Swimmable 接口类型引用 Dog 对象
        Swimmable swimmableDog = new Dog();
        swimmableDog.swim();
        
        // 验证 Dog 和 Cat 的类型
        System.out.println("\ndog 是 Dog 的实例？" + (dog instanceof Dog));
        System.out.println("dog 是 Swimmable 的实例？" + (dog instanceof Swimmable));
        System.out.println("cat 是 Swimmable 的实例？" + (cat instanceof Swimmable));
    }
}