java/w6/AnimalSystem.java

abstract class Animal {
    public abstract void makeSound();
}
interface Swimmable {
    void swim();
}
class Dog extends Animal implements Swimmable {
    @Override
    public void makeSound() {
        System.out.println("小狗汪汪叫");
    }
    @Override
    public void swim() {
        System.out.println("小狗会游泳");
    }
}
class Cat extends Animal {
    @Override
    public void makeSound() {
        System.out.println("小猫喵喵叫");
    }
}
public class AnimalSystem {
    public static void main(String[] args) {
        Animal animal1 = new Dog();
        Animal animal2 = new Cat();
        animal1.makeSound();
        animal2.makeSound();
        System.out.println("-------------------");
        if (animal1 instanceof Swimmable) {
            Swimmable swimmer = (Swimmable) animal1;
            swimmer.swim();
        }
        if (animal2 instanceof Swimmable) {
            Swimmable swimmer = (Swimmable) animal2;
            swimmer.swim();
        } else {
            System.out.println("小猫不会游泳");
        }
    }
}