java 对象转型

1.一个基类的引用类型变量可以“指向”其子类的对象

2.一个基类的引用不可以访问其子类对象新增加的成员属性和方法

3.可以使用 【引用变量 instanceof  类名】来判断该引用变量所指向的对象时候属于该类或该类的子类

4.子类的对象，可以当做基类的对象来使用，称作向上转型（upcasting）,反之称为向下转型(downcasting)

 

class Animal {
  private String name;
  Animal(String name) {this.name = name;}
  
  public void enjoy(){
    System.out.println("叫声......");
  }

 
}

class Cat extends Animal {
  private String eyesColor;
  Cat(String n,String c) {super(n); eyesColor = c;}

  public void enjoy() {
    System.out.println("猫叫声......");
  }

}

class Dog extends Animal {
  private String furColor;
  Dog(String n,String c) {super(n); furColor = c;}
 
  public void enjoy() {
    System.out.println("狗叫声......");
  }
}

class Bird extends Animal {
	 Bird() {
	 	 super("bird");
	 }
	 public void enjoy() {
    System.out.println("鸟叫声......");
  }
}

class Lady {
    private String name;
    private Animal pet;
    Lady(String name,Animal pet) {
        this.name = name; this.pet = pet;
    }
    public void myPetEnjoy(){pet.enjoy();}
}

public class Test {
    public static void main(String args[]){
        Cat c = new Cat("catname","blue");
        Dog d = new Dog("dogname","black");
        Bird b = new Bird();
        Lady l1 = new Lady("l1",c);
        Lady l2 = new Lady("l2",d);
       
        l1.myPetEnjoy();
        l2.myPetEnjoy();

    }
}