Concept
1. Downward transformation is the conversion of parent class objects into subclass objects. We give a reference of the Animal type from the parent class to a Bird type reference. This is a downward transformation.
2. The format is
子类 子类对象=(子类)父类实例
Note
Be sure to perform forced type conversion when converting downward
Example
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 } }
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