在Java中如何实现多态调用与对象替换_OOP多态对象替换方法分享

class Animal {
    void makeSound() {
        System.out.println("Animal makes a sound");
    }
}

class Dog extends Animal {
    @Override
    void makeSound() {
        System.out.println("Woof!");
    }
}

class Cat extends Animal {
    @Override
    void makeSound() {
        System.out.println("Meow!");
    }
}

public class TestPolymorphism {
    public static void main(String[] args) {
        Animal a1 = new Dog();
        Animal a2 = new Cat();

        a1.makeSound(); // 输出: Woof!
        a2.makeSound(); // 输出: Meow!
    }
}

Animal[] animals = {new Dog(), new Cat(), new Dog()};
for (Animal animal : animals) {
    animal.makeSound(); // 自动调用对应子类的方法
}

void playWithPet(Animal pet) {
    pet.makeSound();
}

class Parent {
    String name = "Parent";
    void show() { System.out.println(name); }
}

class Child extends Parent {
    String name = "Child";
}

Parent p = new Child();
System.out.println(p.name); // 输出: Parent
p.show();                   // 输出: Parent（因为show未被重写）

Animal a = new Dog();
((Dog) a).fetch(); // 强制转型后调用Dog特有方法