java向下转型是什么意思

子类 子类对象=（子类）父类实例

class Animal {

    public String name;

    public void eat() {

        System.out.println(this.name + " 正在吃");

    }

}

class Cat extends Animal {

}

class Bird extends Animal {

    public int age;

    public void fly() {

        System.out.println(this.name+"起飞");

    }

}

public class Test extends TestDemo {

    public static void main(String[] args) {

        Animal animal = new Animal();

        Bird bird = (Bird) animal;//必须进行强制类型转换

    }

}