设计模式 随笔（一）

命令模式，active object模式：

需要一个执行引擎，一个执行接口（规约），若干个实现类。

如 开关 后边接 电扇--》电扇开关

接电视：电视开关

空调：空调开关

开关（引擎并不知道要做什么），由后边的电器实现。也就意味着，电器要实现可开关接口。

可以实现多线程，通过控制条件如时间。RTC线程。通过返回非空对象实现do 和 undo。

public void execute();

public object do();

public object undo();

package advanceobject;

import java.util.LinkedList;

public class ActiveObjectEngine {
	LinkedList itsCommands = new LinkedList();
	public void addCommand(Command c){
		itsCommands.add(c);
	}
	
	public void run() throws Exception{
		while(!itsCommands.isEmpty()){
			Command c=(Command) itsCommands.getFirst();
			itsCommands.removeFirst();
			c.execute();
		}
	}
	
	
}

package advanceobject;

public interface Command {
	public void execute() throws Exception;
}

package advanceobject;

public class SleepCommand implements Command {

	private Command wakeupCommand = null;
	private ActiveObjectEngine engine=null;
	private long sleepTime = 0;
	private long startTime = 0;
	private boolean started = false;
	private String objectname=null;
	private int count=0;
	
	public SleepCommand(Command wakeupCommand, ActiveObjectEngine engine,
			long sleepTime,String objname) {
		super();
		this.wakeupCommand = wakeupCommand;
		this.engine = engine;
		this.sleepTime = sleepTime;
		this.objectname=objname;
	}



	@Override
	public void execute() throws Exception {
		// TODO Auto-generated method stub
		long currentTime = System.currentTimeMillis();
		if(!started){
			System.out.println("Init control flag and ready to run");
			started = true;
			startTime=currentTime;
			engine.addCommand(this);
		}
		else if((currentTime-startTime)<sleepTime){
			System.out.println("Running do some business before condition is false "+objectname+" times "+count);
			count++;
			engine.addCommand(this);
		}
		else
		{
			System.out.println("Time out add exit into loop");
			if(null!=wakeupCommand)
				engine.addCommand(wakeupCommand);
		}
	}

}

package advanceobject;

public class TestMain {
	
	public static void main(String[] args){
		Command wakeup = null;
		ActiveObjectEngine e=new ActiveObjectEngine();
		SleepCommand c1=new SleepCommand(wakeup,e,10,"c1");
		e.addCommand(c1);
		SleepCommand c2=new SleepCommand(wakeup,e,10,"c2");
		e.addCommand(c2);
		SleepCommand c3=new SleepCommand(wakeup,e,10,"c3");
		e.addCommand(c3);
		SleepCommand c4=new SleepCommand(wakeup,e,10,"c4");
		e.addCommand(c4);
		try {
			e.run();
		} catch (Exception e1) {
			// TODO Auto-generated catch block
			e1.printStackTrace();
		}
	}
}