5|3多态中静态成员函数（变量）的特点

无论编译还是运行，都参考左边。静态类型，静态绑定。非静态类型，动态绑定。

class Fu { static void method1() { System.out.println("Fu_Method_1"); } } class Zi extends Fu { static void method1() { System.out.println("Zi_Method_1"); } } public class Demo5 { public static void main(String[] args) { Fu f = new Zi(); f.method1(); Zi z = new Zi(); z.method1(); } }

运行结果：

Fu_Method_1 Zi_Method_1

6|0多态-转型

abstract class Animal { public abstract void eat(); } class Cat extends Animal { @Override

public void eat() { System.out.println("eat fish"); } public void CatchMouse() { System.out.println("CatchMouse"); } } class Dog extends Animal { @Override

public void eat() { System.out.println("eat bone"); } public void GuardHouse() { System.out.println("GuardHouse"); } } class Monkey extends Animal { @Override

public void eat() { System.out.println("eat banana"); } public void PlayBall() { System.out.println("Play Ball"); } } public class Demo1 { public static void main(String[] args) { function(new Cat()); function(new Dog()); function(new Monkey()); } public static void function(Animal a) { a.eat(); if (a instanceof Cat) { //instanceof关键字用于判断所属类型 Cat c = (Cat)a; //向下转型 c.CatchMouse(); } else if (a instanceof Dog) { Dog d = (Dog)a; //向下转型 d.GuardHouse(); } else { Monkey m = (Monkey)a;//向下转型 m.PlayBall(); } } }

运行结果：

eat fish CatchMouse eat bone GuardHouse eat banana Play Ball

7|0多态的应用

以电脑主板为例的示例分析电脑主板要考虑到拓展性，使用了pci接口，板卡（声卡，网卡等）和主板都遵循pci接口。

interface Pci { public void open(); public void close(); }

class MainBoard { public void run() { System.out.println("Main Board run"); } public void usePci(Pci p){ //接口类型指向自己的子类对象

if(p != null){ //加入判断防止空指针 p.open(); p.close(); } } } class Netcard implements Pci { @Override

public void open() { System.out.println("Netcard open"); }

@Override

public void close() { System.out.println("Netcard close"); } } class Soundcard implements Pci { @Override

public void open() { System.out.println("Soundcard open"); }

@Override

public void close() { System.out.println("Soundcard close"); } } public class Demo6 { public static void main(String[] args) { MainBoard mb = new MainBoard(); mb.run(); mb.usePci(null); mb.usePci(new Netcard()); mb.usePci(new Soundcard()); } }

运行结果

Main Board run Netcard open Netcard close Soundcard open Soundcard close

__EOF__

本文作者：Liyuxin 本文链接：https://www.cnblogs.com/liyuxin2/p/12313781.html

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Java学习笔记(十一)面向对象---多态(2)

5|3多态中静态成员函数（变量）的特点

6|0多态-转型

7|0多态的应用