java之多态(Polymorphic)动态绑定(Dynamic Binding)迟绑定(Late Binding)

Posted 2020-08-07

今天，我们来说说java面向对象最核心的东西，多态。通过多态可以使我们的程序可复用性达到极致，这就是我们为什么要学多态的原因。

“多态”(Polymorphic)也叫“动态绑定”(Dynamic Binding)同时也叫“迟绑定”(Late Binding)。

动态绑定是指“在执行期间（而非编译期间）判断所引用对象的实际类型，根据其实际类型调用其相应的方法。”

程序代码：

public class TestPolymorphic{
    public static void main(String args[]){
    
        Animal animal = new Animal("animal");
        Cat cat = new Cat("cat","blue");
        Dog dog = new Dog("dog","black");
        
        Lily l1 = new Lily("l1",animal);
        Lily l2 = new Lily("l1",dog);
        
        l1.myAnimalEnjoy();
        l2.myAnimalEnjoy();
    }
}
class Lily{
    private String name;
    private Animal animal;
    public Lily(String name, Animal animal){
        this.name = name;
        this.animal = animal;
    }
    public void myAnimalEnjoy(){
        animal.enjoy();
    }
}
class Animal{
    private String name;
    public Animal(String name){
        this.name = name;
    }
    public void enjoy(){
        System.out.println("叫声~~~");
    }
}
class Dog extends Animal{
    
    private String forlorColor;
    public Dog(String name,String forlorColor){
        super(name);
        this.forlorColor = forlorColor;
    }
    public void enjoy(){
        System.out.println("dog叫声~~~");
    }
}
class Cat extends Animal{
    
    private String eyesColor;
    public Cat(String name,String eyesColor){
        super(name);
        this.eyesColor = eyesColor;
    }
    public void enjoy(){
        System.out.println("cat叫声~~~");
    }
}

程序运行结果：

总结：通过以上示例，我们发现多态必备的三个条件1、有继承2、有重写3、父类引用指向子类对象