学步园

/**多态是指执行期间（而非编译期间）判断所印象对象的实际类型，根据其实际的类型调用相应的方法。
 多态存在的三个必要条件：
    一、要有继承
    二、要有重写
    三、父类引用指向子类对象
 多态的有点：
    使得程序的扩张性达到极致
  */
abstract class Animal {
  private String name;
  Animal(String name) {this.name = name;}
 
  public void enjoy(){
    System.out.println("叫声......");
  }
 
//  public abstract void enjoy();
}

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......");
  }
 
  //public abstract void enjoy();
}

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);
        Lady l3 = new Lady("l3",b);
        l1.myPetEnjoy();
        l2.myPetEnjoy();
        l3.myPetEnjoy();
    }
}