Java新手学习笔记---多态

public class testpolymorphism {
    public static void main(String[] args) {
         animal a = new cat();
         testVoice(a);
        //testVoice(new cat());
    }
    public static void testVoice(animal a){
        a.voice();
        if(a instanceof cat){
            ((cat)a).catchmouse();
        }
    }
}
class animal {
    String name;
    public void voice(){
        System.out.println("aaaaa");
    }
}
class cat extends animal{
    public void voice(){
        System.out.println("nya");
    }
    public void catchmouse(){
        System.out.println("抓");
    }
}
class dog extends animal{
    public void voice(){
        System.out.println("wang");
    }
}

nya
抓