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。