Java vs. C# delegate

最新推荐文章于 2024-08-18 19:16:03 发布

转载最新推荐文章于 2024-08-18 19:16:03 发布 · 1.9k 阅读

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本文通过Java反射技术展示了如何实现方法调用，并通过示例代码解释了反射原理及应用。

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

Java

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

C#
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;

 
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;