如何定义方法的返回类型是超类的实现

public class Animal {
    public void eat() {
        System.out.println("Animal is eating.");
    }
}

public class Dog extends Animal {
    @Override
    public void eat() {
        System.out.println("Dog is eating.");
    }

    public void bark() {
        System.out.println("Dog is barking.");
    }
}

public class Cat extends Animal {
    @Override
    public void eat() {
        System.out.println("Cat is eating.");
    }

    public void meow() {
        System.out.println("Cat is meowing.");
    }
}

public class Main {
    public static Animal getAnimal() {
        // 返回类型为Animal，可以返回Animal的任何子类对象
        return new Dog();
    }

    public static void main(String[] args) {
        Animal animal = getAnimal();
        animal.eat();  // 输出：Dog is eating.
        
        // 由于animal的类型是Animal，无法调用子类特有的方法
        // animal.bark();  // 编译错误
        
        // 可以将animal强制转换为Dog类型，然后调用子类特有的方法
        if (animal instanceof Dog) {
            Dog dog = (Dog) animal;
            dog.bark();  // 输出：Dog is barking.
        }
    }
}