Java多態:upcast和downcast

標籤：

upcast例:

public class Test{    public static void main(String[] args)    {         Cup aCup = new BrokenCup();        aCup.addWater(10); // method binding    }}class Cup {    public void addWater(int w)     {        this.water = this.water + w;    }    public void drinkWater(int w)    {        this.water = this.water - w;    }    private int water = 0;}class BrokenCup extends Cup{    public void addWater(int w)     {        System.out.println("shit, broken cup");    }    public void drinkWater(int w)    {        System.out.println("om...num..., no water inside");    }}

 

downcast例:

public class TestJavaDemo{    public static void main(String[] args) {        Person p=new Student();        Student s=(Student)p;        s.fun1();        s.fun2();    }}class Person{    public void fun1(){        System.out.println("1.Person{fun1()}");    }    public void fun2(){        System.out.println("2.Person{fun2()}");    }}class Student extends Person{    public void fun1(){        System.out.println("3.Student{fun1()}");    }    public void fun3(){        System.out.println("4.Student{fun3()}");    }}

 

Java多態:upcast和downcast