Java与.net的区别delegate和event

There is no delegate concept in Java
The right-side C# program may be mimiced 
with reflection technology.

在Java中没有delegate的概念，而C#中delegate使用的是类似Java中反射的工具。

import java.lang.reflect.*;
import java.io.*;
public class Test
{
    public static void main(String[] args) throws Exception
    {
        String[] list= {"to","be","or","not","to","be"};
        Method m1 = Test.class.getMethod("toConsole",new Class[] {String.class});
        Display(m1, list);
        Method m2 = Test.class.getMethod("toFile",new Class[] {String.class});
        Display (m2, list);
    }
    public static void toConsole (String str)
    {
        System.out.print(str+" ");
    }
    public static void toFile (String s)
    {
        File f = new File("delegate.txt");
        try{
            PrintWriter fileOut = 
               new PrintWriter(new FileOutputStream(f));
            fileOut.write(s);
            fileOut.flush();
            fileOut.close();
        }catch(IOException ioe) {}
    }
    public static void display(Method m, String[] list)
    {
        for(int k = 0; k < list.length; k++) {
            try {
                Object[] args = {new String(list[k])};
                m.invoke(null, args);
            }catch(Exception e) {}
        }
    }
}
 

Delegate是引用类型允许间接访问方法。以下是简单和多维的委托Delegate

Delegates are reference types which allow 
indirect calls to methods. There are single and multicast
delegates.
============================================
 using System;
 using System.IO;
 public class DelegateTest
 {
     public delegate void Print (String s);
     public static void Main()
     {
         Print s = new Print (toConsole);
         Print v = new Print (toFile);
         Display (s);
         Display (v);
     }
     public static void toConsole (String str)
     {
         Console.WriteLine(str);
     }
     public static void toFile (String s)
     {
         File f = new File("delegate.txt");
         StreamWriter fileOut = f.CreateText();
         fileOut.WriteLine(s);
         fileOut.Flush();
         fileOut.Close();
     }
     public static void Display(Print pMethod)
     {
         pMethod("This should be displayed in the console");
     }
 }

 A delegate instance encapsulates one or more methods, 
 each of which is referred to as a callable entity. 
 To add or reduce a list of calls
 by using operators += or -=.
 for example
 Print p = s + v;
 s += v;

对比可以得出的概念是：Java中没有这个Delegate的概念，但是通过反射的方法可以实现，C#却可以通过直接使用Delegate用来实现函数方法的间接调用。