JAVA设计模式---命令模式

/* 遥控器命令接口，实现遥控器的动作 */
public interface Command {
    public void execute();
    public void undo();
}

/* 空对象，用于返回一个没有意义的对象*/
public class NoCommand implements Command{
    @Override
    public void execute() {

    }

    @Override
    public void undo() {

    }
}

public class Light {
    private String name;

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

    public Light() {
    }

    public void lightOn(){
        System.out.println(name  + " light is on!");
    }

    public void lightOff(){
        System.out.println(name  + " light is off!");
    }
}

public class LightOnCommand implements Command {
    Light light = new Light();
    public LightOnCommand(Light light) {
        this.light = light;
    }

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

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

public class LightOffCommand implements Command {
    Light light = new Light();

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

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

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

public class RemoteControl {
    Command[] onCommands;
    Command[] offCommands;
    Command undoCommand;

    public RemoteControl() {
        onCommands = new Command[7];
        offCommands = new Command[7];
        Command noCommand = new NoCommand();
        for(int i=0;i<7;i++){
            onCommands[i] = noCommand;
            offCommands[i] = noCommand;
        }
        undoCommand = noCommand;
    }

    public void setCommand(int slot,Command onCommand,Command offCommand){
        onCommands[slot] = onCommand;
        offCommands[slot] = offCommand;
    }

    public void onButtonWasPushed(int slot){
        onCommands[slot].execute();
        undoCommand = onCommands[slot];
    }

    public void offButtonWasPushed(int slot){
        offCommands[slot].execute();
        undoCommand = offCommands[slot];
    }

    public void undoButtonWasPushed(){
        undoCommand.undo();
    }

    @Override
    public String toString() {
        StringBuffer strBuff = new StringBuffer();
        strBuff.append("\n===========Remote Control=============\n");
        for(int i=0;i<onCommands.length;i++){
            strBuff.append("[slot "+i+"]"+onCommands[i].getClass().getName()+"   "
            +offCommands[i].getClass().getName()+"\n");
        }
        return strBuff.toString();
    }
}

public class RemoteLoader {
    public static void main(String[] args) {
        RemoteControl remoteControl = new RemoteControl();

        Light livingRoomLight = new Light("living Room");
        Light kitchenLight = new Light("kitchen");
        Light washingRoomLight = new Light("washing Room");

        LightOnCommand livingRoomLightOn = new LightOnCommand(livingRoomLight);
        LightOffCommand livingRoomLightOff = new LightOffCommand(livingRoomLight);

        LightOnCommand kitchenLightOn = new LightOnCommand(kitchenLight);
        LightOffCommand kitchenLightOff = new LightOffCommand(kitchenLight);

        LightOnCommand washingRoomLightOn = new LightOnCommand(washingRoomLight);
        LightOffCommand washingRoomLightOff = new LightOffCommand(washingRoomLight);

        remoteControl.setCommand(0,livingRoomLightOn,livingRoomLightOff);
        remoteControl.setCommand(1,kitchenLightOn,kitchenLightOff);
        remoteControl.setCommand(2,washingRoomLightOn,washingRoomLightOff);

        System.out.println(remoteControl);

        remoteControl.onButtonWasPushed(0);
        remoteControl.onButtonWasPushed(1);
        remoteControl.onButtonWasPushed(2);
        remoteControl.offButtonWasPushed(0);
        remoteControl.offButtonWasPushed(1);
        remoteControl.offButtonWasPushed(2);
        remoteControl.undoButtonWasPushed();
    }
}