Java用反射实现C#的Delegate

来源：互联网发布：windows mac 编辑：程序博客网时间：2024/06/08 02:56

在java中没有Delegate，但是可以通过反射实现。

我们假设有一只猫类和老鼠类。猫叫的时候老鼠就跑。但是老鼠不知道猫什么时候叫，因此我们需要一个事件去通知老鼠，告诉它们猫来了。那么这个事件我们可以用Delegate来实现。

首先，我们先针对静态方法去实现。

using System;namespace DeletegateTest{    class Mouse    {        private string name;        public Mouse(string name)        {            this.name = name;        }        public static void Run()        {            Console.WriteLine("Cat is coming，run.");        }    }    class Cat    {        private string name;        public Cat()        {            this.name = "Unkonw";        }        public Cat(string name)        {            this.name = name;        }        public delegate void CatShoutEventHandler();        public event CatShoutEventHandler catShout;        public void Shout()        {            Console.WriteLine("Miao，I am {0}", name);            if (catShout != null)            {                catShout();            }        }        public static void Main(string[] args)        {            Cat tom = new Cat("Tom");            tom.catShout = Mouse.Run;            tom.Shout();        }    }}

此时，运行结果如下。我们看到，我们调用了猫叫的方法，老鼠就跑了。

下面我们用Java实现：

import java.lang.reflect.Method;class Mouse {private String name;public Mouse(String name){this.name = name;}public static void Run(){System.out.println("Cat is coming,run");}}public class Cat {private String name;public Method CatShout;public Cat(String name){this.name = name;}public void Shout(){System.out.println("Miao,I am " + name);if(CatShout != null){try {CatShout.invoke(null);} catch (Exception e) {System.out.println("error");}}}public static void main(String[] args) throws Exception{Cat tom = new Cat("Tom");tom.CatShout = Mouse.class.getMethod("Run");tom.Shout();}}

结果和刚才C#的运行是一样滴。

现在我们假设有这样一个需求：我们通知老鼠是哪一只猫来了，并且通知每一只老鼠以便让大家共存亡。即就是通知老鼠猫来时需要知道猫的名字，并且将刚才的静态run方法作为实例化方法。

代码分别如下：

using System;namespace DeletegateTest{    class Mouse    {        private string name;        public Mouse(string name)        {            this.name = name;        }        public void Run(string catName)        {            Console.WriteLine("Cat {0} is coming，run.I am {1}", catName, name);        }    }    class Cat    {        private string name;        public Cat()        {            this.name = "Unkonw";        }        public Cat(string name)        {            this.name = name;        }        public delegate void CatShoutEventHandler(string name);        public event CatShoutEventHandler catShout;        public void Shout()        {            Console.WriteLine("Miao，I am {0}", name);            if (catShout != null)            {                catShout(name);            }        }        public static void Main(string[] args)        {            Cat tom = new Cat("Tom");            Mouse jerry = new Mouse("Jeery");            Mouse jack = new Mouse("Jack");            tom.catShout = jerry.Run;            tom.catShout += jack.Run;            tom.Shout();        }    }}

package com.refelection.delegate;import java.lang.reflect.Method;class Mouse {private String name;public Mouse(String name){this.name = name;}public void Run(String name){System.out.println("Cat " + name +  " is coming,run.I am " + this.name);}}public class Cat {private String name;public Method CatShout;public Cat(String name){this.name = name;}public void Shout(Mouse[] mouse){System.out.println("Miao,I am " + name);if(CatShout != null){try {for(Mouse m : mouse){CatShout.invoke(m, new Object[]{name});}} catch (Exception e) {System.out.println("error");}}}public static void main(String[] args) throws Exception{Cat tom = new Cat("Tom");Mouse jerry = new Mouse("Jerry");Mouse jack = new Mouse("Jack");tom.CatShout = jerry.getClass().getMethod("Run", new Class[]{ String.class });tom.Shout(new Mouse[] {jerry,jack});}}

0 0