设计模式——命令模式

public interface Command {

    void execute();

    void undo();
}

public class LightOffCommand implements Command {

    private Light light = new Light();

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

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

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

public class LightOnCommand implements Command {

    private Light light = new Light();

    public LightOnCommand() {
        this.light = light;
    }

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

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

public class Light {

    public void on() {
        System.out.println("Light is on");
    }

    public void off() {
        System.out.println("Light is off");
    }
}

public class NoCommand implements Command {

    @Override
    public void execute() {

    }

    @Override
    public void undo() {

    }
}

public class StereoOffWithCDCommand implements Command {

    private Stereo stereo = new Stereo();

    public StereoOffWithCDCommand() {
        this.stereo = stereo;
    }

    @Override
    public void execute() {
        stereo.off();
    }

    @Override
    public void undo() {
        stereo.on();
        stereo.setCD();
        stereo.setVolume(11);
    }
}

public class StereoOnWithCDCommand implements Command {

    private Stereo stereo = new Stereo();

    public StereoOnWithCDCommand() {
        this.stereo = stereo;
    }

    @Override
    public void execute() {
        stereo.on();
        stereo.setCD();
        stereo.setVolume(11);
    }

    @Override
    public void undo() {
        stereo.off();
    }
}

public class Stereo {

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

    public void setCD() {
        System.out.println("CD is set");
    }

    public void setVolume(int volume) {
        System.out.println("Volume is set " + volume);
    }

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

public class RemoteControl {

    private Command[] onCommands;
    private Command[] offCommands;
    private Command undoCommand;

    public RemoteControl() {
        onCommands = new Command[2];
        offCommands = new Command[2];

        Command command = new NoCommand();
        for (int i = 0; i < 2; i++) {
            onCommands[i] = command;
            offCommands[i] = command;
        }
        undoCommand = command;
    }

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

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

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

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

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

        return stringBuffer.toString();
    }
}

public class RemoteControlTest {

    public static void main(String[] args) {

        RemoteControl remte = new RemoteControl();
        LightOnCommand lightOnCommand = new LightOnCommand();
        LightOffCommand lightOffCommand = new LightOffCommand();
        StereoOnWithCDCommand onWithCDCommand = new StereoOnWithCDCommand();
        StereoOffWithCDCommand offWithCDCommand = new StereoOffWithCDCommand();

        remte.setCommand(0, lightOnCommand, lightOffCommand);
        remte.setCommand(1, onWithCDCommand, offWithCDCommand);

        System.out.println(remte.toString());

        remte.onButtonWasPush(0);
        remte.onButtonWasPush(1);
        remte.offButtonWasPush(0);
        remte.offButtonWasPush(1);

        remte.undoButtonWasPushed();
    }
}