NullRobot.java

package thinkinginjava.typeinfo;

// Using a dynamic proxy to create a Null Object.
import java.lang.reflect.*;
import java.util.*;

import thinkinginjava.util.Null;

class NullRobotProxyHandler implements InvocationHandler {
	private String nullName;
	private Robot proxied = new NRobot();

	NullRobotProxyHandler(Class<? extends Robot> type) {
		nullName = type.getSimpleName() + " NullRobot";
	}

	private class NRobot implements Null, Robot {
		public String name() {
			return nullName;
		}

		public String model() {
			return nullName;
		}

		public List<Operation> operations() {
			return Collections.emptyList();
		}
	}

	public Object invoke(Object proxy, Method method, Object[] args)
			throws Throwable {
		return method.invoke(proxied, args);
	}
}

public class NullRobot {
	public static Robot newNullRobot(Class<? extends Robot> type) {
		return (Robot) Proxy.newProxyInstance(NullRobot.class.getClassLoader(),
				new Class[] { Null.class, Robot.class },
				new NullRobotProxyHandler(type));
	}

	public static void main(String[] args) {
		Robot[] bots = { new SnowRemovalRobot("SnowBee"),
				newNullRobot(SnowRemovalRobot.class) };
		for (Robot bot : bots)
			Robot.Test.test(bot);
	}
}