java/main/w6/Animals.java

// 抽象类Animal
abstract class Animal {
    // 抽象方法makesound()
    public abstract void makesound();
}

// 接口Swimmable
interface Swimmable {
    // 方法swim()
    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("Dog barks: Woof! Woof!");
    }
    
    @Override
    public void swim() {
        System.out.println("Dog is swimming");
    }
}

// Cat类继承Animal
class Cat extends Animal {
    @Override
    public void makesound() {
        System.out.println("Cat meows: Meow! Meow!");
    }
}

public class Animals {
    public static void main(String[] args) {
        // 多态测试
        Animal animal1 = new Dog();
        Animal animal2 = new Cat();
        
        System.out.println("Testing polymorphism:");
        animal1.makesound();
        animal2.makesound();
        
        // 测试Dog的swim方法
        System.out.println("\nTesting swim method:");
        if (animal1 instanceof Swimmable) {
            ((Swimmable) animal1).swim();
        }
        
        if (animal2 instanceof Swimmable) {
            ((Swimmable) animal2).swim();
        } else {
            System.out.println("Cat cannot swim");
        }
    }
}