命令模式

Commands.java

import static com.mceiba.util.Print.*;
import java.util.*;

interface Command { void action(); }
enum Signal { RED, YELLOW, GREEN }
public class Commands{
	public static void main(String[] args){
		EnumMap<Signal, Command> em = new EnumMap<Signal, Command>(Signal.class);
		em.put(Signal.RED, new Command(){
			public void action() { println("stop"); }
		});
		em.put(Signal.YELLOW, new Command(){
			public void action() { println("wait"); }
		});
		em.put(Signal.GREEN, new Command(){
			public void action() { println("go"); }
		});
		for(Map.Entry<Signal, Command> e : em.entrySet()){
			print(e.getKey()+": ");
			e.getValue().action();
		}
	}
}