JAVA通过反映方法实现C#的委托

C#委托实现了类内部的方法暴露给调用者，类似C++中的方法指针，方法以返回值的形式传递。这种设计方式可以实现统一方法名。

Java代码







import java.util.*;
import java.lang.reflect.*;

interface Command {
Method executeMethod();
}

class StartComputer implements Command {

Class classType = StartComputer.class;
public Method executeMethod() {
try {
return classType.getMethod("innerMethod",
new Class[]{ int.class });

} catch(NoSuchMethodException e) {
e.printStackTrace();
return null;
}
}

public void innerMethod(int param) {

// TODO: something.
System.out.println("----------------- OUTPUT ------------------");

System.out.println(param);
}
}

public class CommandStudy {

public static Map<String, Class> commandMap =
new HashMap<String, Class>();
static {
commandMap.put("StartComputer", StartComputer.class);

}
public static
void main(String[] args) throws IllegalAccessException, InstantiationException , InvocationTargetException{

Class startComputerClass = commandMap.get("StartComputer");

Command someCommand = (Command)startComputerClass.newInstance();
Method executeMethod = someCommand.executeMethod();
executeMethod.invoke(someCommand, new Object[] {
new Integer(200) });
}
}

import java.util.*;
import java.lang.reflect.*;

interface Command {
Method executeMethod();
}

class StartComputer implements Command {
Class classType = StartComputer.class;
public Method executeMethod() {
try {
return classType.getMethod("innerMethod", new Class[]{ int.class });
} catch(NoSuchMethodException e) {
e.printStackTrace();
return null;
}
}

public void innerMethod(int param) {
// TODO: something.
System.out.println("----------------- OUTPUT ------------------");
System.out.println(param);
}
}

public class CommandStudy {
public static Map<String, Class> commandMap = new HashMap<String, Class>();
static {
commandMap.put("StartComputer", StartComputer.class);
}
public static void main(String[] args) throws IllegalAccessException, InstantiationException , InvocationTargetException{
Class startComputerClass = commandMap.get("StartComputer");
Command someCommand = (Command)startComputerClass.newInstance();
Method executeMethod = someCommand.executeMethod();
executeMethod.invoke(someCommand, new Object[] { new Integer(200) });
}
}

Command类是公共接口类，对外开放的接口方法。StartCommand实现一个Command接口。在StartCommand的executeMethod方法的内部实现了方法的转移，把StartCommand里其它方法转移到接口方法executeMethod里，这样设计后，统一方法接口。

C#中委托对象delegate与JAVA中Method对象主要区别在于delegate里包含方法的对象，而Method主要是对方法的描述，不包含任务对象信息。

JAVA中用invoke方法时可能会产生大量的异常。