感想

命令模式：将请求、命令、动作等封装成对象，这样可以让项目使用这些对象来参数化其他对象。是的命令的请求者和执行者解耦。

例子以一行2个按钮的遥控器作示范。

如下图所示，若添加新的设备，则需要在该类中添加新的成员变量，及实现的方法中添加更多的代码，使得代码耦合度高，相互依赖大，影响后期的维护以及开发。

1.将请求、命令、动作等分类为一个接口，可以当作为执行命令，如下：

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public interface Command {
	public void execute();
	public void undo();
}

2.设备类，如下：

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public class Light {

	String loc = "";

	public Light(String loc) {
		this.loc = loc;
	}

	public void On() {
		System.out.println(loc + " On");
	}

	public void Off() {
		System.out.println(loc + " Off");
	}

}
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public class Stereo {
	static int volume = 0;

	public void On() {
		System.out.println("Stereo On");
	}

	public void Off() {
		System.out.println("Stereo Off");
	}

	public void SetCd() {
		System.out.println("Stereo SetCd");
	}

	public void SetVol(int vol) {
		volume = vol;
		System.out.println("Stereo volume=" + volume);
	}

	public int GetVol() {
		return volume;
	}

	public void Start() {
		System.out.println("Stereo Start");
	}
}

3.将遥控器上面的按钮划分为3种，如下：

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public interface Control {

	public void onButton(int slot);

	public void offButton(int slot);

	public void undoButton();
}

4.设置设备的命令，如灯的开关，音响的开关，设置音响的大小声量，如下：

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public class LightOffCommand implements Command {
	private Light light;

	public LightOffCommand(Light light) {
		this.light = light;
	}

	@Override
	public void execute() {
		light.Off();
	}

	@Override
	public void undo() {
		light.On();
	}

}
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public class LightOffCommand implements Command {
	private Light light;

	public LightOffCommand(Light light) {
		this.light = light;
	}

	@Override
	public void execute() {
		light.Off();
	}

	@Override
	public void undo() {
		light.On();
	}

}
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public class StereoAddVolCommand implements Command {
	private Stereo setreo;

	public StereoAddVolCommand(Stereo setreo) {
		this.setreo = setreo;
	}

	@Override
	public void execute() {
		int vol = setreo.GetVol();
		if (vol < 11) {
			setreo.SetVol(++vol);
		}
	}

	@Override
	public void undo() {
		int vol = setreo.GetVol();
		if (vol > 0) {
			setreo.SetVol(--vol);
		}
	}
}
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public class StereoOffCommand implements Command {
	private Stereo setreo;

	public StereoOffCommand(Stereo setreo) {
		this.setreo = setreo;
	}

	@Override
	public void execute() {
		setreo.Off();
	}

	@Override
	public void undo() {
		setreo.On();
		setreo.SetCd();
	}

}
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public class StereoOnCommand implements Command {
	private Stereo setreo;

	public StereoOnCommand(Stereo setreo) {
		this.setreo = setreo;
	}

	@Override
	public void execute() {
		setreo.On();
		setreo.SetCd();
	}

	@Override
	public void undo() {
		setreo.Off();
	}

}
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public class StereoSubVolCommand implements Command {
	private Stereo setreo;

	public StereoSubVolCommand(Stereo setreo) {
		this.setreo = setreo;
	}

	@Override
	public void execute() {
		int vol = setreo.GetVol();
		if (vol > 0) {
			setreo.SetVol(--vol);
		}
	}

	@Override
	public void undo() {
		int vol = setreo.GetVol();
		if (vol < 11) {
			setreo.SetVol(++vol);
		}
	}
}

5.可以设置按钮为空命令模式，如下：

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public class NoCommand implements Command {

	@Override
	public void execute() {
	}

	@Override
	public void undo() {
	}
}

6.可以设置组合键，如下：

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public class MarcoCommand implements Command {

	private Command[] commands;

	public MarcoCommand(Command[] commands) {
		this.commands = commands;
	}

	@Override
	public void execute() {
		for (int i = 0, len = commands.length; i < len; i++) {
			commands[i].execute();
		}
	}

	@Override
	public void undo() {
		for (int i = commands.length - 1; i >= 0; i--) {
			commands[i].undo();
		}
	}
}

7.实现遥控器，如下：

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public class CommandModeControl implements Control {
	private Command[] onCommands;
	private Command[] offCommands;
	private Stack<Command> stack = new Stack<Command>();

	public CommandModeControl() {
		//设置6行的按钮，每行按钮有2个
		onCommands = new Command[5];
		offCommands = new Command[5];

		Command noCommand = new NoCommand();

		//默认初始化的时候按钮处于空命令模式，此处的作用用于不用在onButton，offButton和undoButton中判断对象。
		for (int i = 0, len = onCommands.length; i < len; i++) {
			onCommands[i] = noCommand;
			offCommands[i] = noCommand;
		}

	}

	//设置每行按钮的需要执行的命令，此处每行有2个按钮，则需要传递2个命令以及对于的行数
	public void setCommand(int slot, Command onCommand, Command offCommand) {
		onCommands[slot] = onCommand;
		offCommands[slot] = offCommand;

	}

	@Override
	public void onButton(int slot) {

		onCommands[slot].execute();
		stack.push(onCommands[slot]);
	}

	@Override
	public void offButton(int slot) {

		offCommands[slot].execute();
		stack.push(offCommands[slot]);
	}

	@Override
	public void undoButton() {
		stack.pop().undo();
	}

}

8.遥控器的使用，如下：

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public class ControlTest {

	public static void main(String[] args) {
		CommandModeControl control = new CommandModeControl();

		//组合键
		MarcoCommand onmarco, offmarco;

		//不同设备
		Light bedroomlight = new Light("BedRoom");
		Light kitchlight = new Light("Kitch");
		Stereo stereo = new Stereo();

		//灯的命令
		LightOnCommand bedroomlighton = new LightOnCommand(bedroomlight);
		LightOffCommand bedroomlightoff = new LightOffCommand(bedroomlight);
		LightOnCommand kitchlighton = new LightOnCommand(kitchlight);
		LightOffCommand kitchlightoff = new LightOffCommand(kitchlight);

		//灯具有组合使用
		Command[] oncommands = {bedroomlighton, kitchlighton};
		Command[] offcommands = {bedroomlightoff, kitchlightoff};

		onmarco = new MarcoCommand(oncommands);
		offmarco = new MarcoCommand(offcommands);

		//音响的命令
		StereoOnCommand stereoOn = new StereoOnCommand(stereo);
		StereoOffCommand stereoOff = new StereoOffCommand(stereo);
		StereoAddVolCommand stereoaddvol = new StereoAddVolCommand(stereo);
		StereoSubVolCommand stereosubvol = new StereoSubVolCommand(stereo);

		//将灯设置在遥控上，一行2个按钮
		control.setCommand(0, bedroomlighton, bedroomlightoff);
		control.setCommand(1, kitchlighton, kitchlightoff);
		control.setCommand(2, stereoOn, stereoOff);
		control.setCommand(3, stereoaddvol, stereosubvol);
		control.setCommand(4, onmarco, offmarco);

		//使用遥控器
		control.onButton(0);
		control.undoButton();
		//control.offButton(0);
		control.onButton(1);
		control.offButton(1);
		control.onButton(2);
		control.onButton(3);

		control.offButton(3);
		control.undoButton();
		control.offButton(2);
		control.undoButton();
		control.onButton(4);
		control.offButton(4);
	}

}

最后，通过接口的统一并实现接口内的方法，使遥控器中的控制更加容易及规范，加上遥控器中对排列的设计以及记录命令执行的顺序，添加了遥控器的功能，该命令模式在其中运用合理。