Command

src/command/CommandPattern.java

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+package command;
+
+import command.command.impl.*;
+import command.invoker.RemoteControl;
+import command.invoker.RemoteControlWithUndo;
+import command.invoker.SimpleRemoteControl;
+import command.receiver.GarageDoor;
+import command.receiver.Light;
+import command.receiver.Stereo;
+
+/**
+ * 커맨드 패턴에서 클라이언트에 해당하는 클래스
+ */
+public class CommandPattern {
+    public static void main(String[] args) {
+//        simpleRemoteControl();
+//        remoteControl();
+        remoteControlWithUndo();
+    }
+
+    private static void simpleRemoteControl() {
+        final SimpleRemoteControl remote = new SimpleRemoteControl(); // remote 변수 : 인보커(invoker)
+
+        final Light light = new Light(); // light : 리시버
+        final LightOnCommand lightOnCommand = new LightOnCommand(light); // lightOnCommand : 커맨드 객체
+
+        final GarageDoor garageDoor = new GarageDoor(); // 리시버
+        final GarageDoorUpCommand garageDoorUpCommand = new GarageDoorUpCommand(garageDoor); // 커맨드 객체
+
+        remote.setCommand(lightOnCommand); // invoker의 setCommand 메소드로 커맨드 객체를 전달
+        remote.buttonWasPressed(); // invoker로 커맨드 객체의 execute 메소드를 호출
+
+        remote.setCommand(garageDoorUpCommand);
+        remote.buttonWasPressed();
+    }
+
+    private static void remoteControl() {
+        RemoteControl remoteControl = new RemoteControl();
+
+        Light livingRoomLight = new Light("Living Room");
+        Light kitchenLight = new Light("Kitchen");
+        GarageDoor garageDoor = new GarageDoor("Garage");
+        Stereo livingRoomStereo = new Stereo("Living Room");
+
+        LightOnCommand livingRoomLightOnCommand = new LightOnCommand(livingRoomLight);
+        LightOffCommand livingRoomLightOffCommand = new LightOffCommand(livingRoomLight);
+        LightOnCommand kitchenLightOnCommand = new LightOnCommand(kitchenLight);
+        LightOffCommand kitchenLightOffCommand = new LightOffCommand(kitchenLight);
+        GarageDoorUpCommand garageDoorUpCommand = new GarageDoorUpCommand(garageDoor);
+        GarageDoorDownCommand garageDoorDownCommand = new GarageDoorDownCommand(garageDoor);
+        StereoOnWithCDCommand stereoOnWithCDCommand = new StereoOnWithCDCommand(livingRoomStereo);
+        StereoOffCommand stereoOffCommand = new StereoOffCommand(livingRoomStereo);
+
+        remoteControl.setCommand(0, livingRoomLightOnCommand, livingRoomLightOffCommand);
+        remoteControl.setCommand(1, kitchenLightOnCommand, kitchenLightOffCommand);
+        remoteControl.setCommand(2, garageDoorUpCommand, garageDoorDownCommand);
+        remoteControl.setCommand(3, stereoOnWithCDCommand, stereoOffCommand);
+
+        System.out.println(remoteControl);
+
+        for (int i = 0; i < 4; i++) {
+            remoteControl.onButtonWasPushed(i);
+            remoteControl.offButtonWasPushed(i);
+        }
+    }
+
+    private static void remoteControlWithLambda() {
+        RemoteControl remoteControl = new RemoteControl();
+
+        Light livingRoomLight = new Light("Living Room");
+        Light kitchenLight = new Light("Kitchen");
+        GarageDoor garageDoor = new GarageDoor("Garage");
+        Stereo livingRoomStereo = new Stereo("Living Room");
+
+        StereoOnWithCDCommand stereoOnWithCDCommand = new StereoOnWithCDCommand(livingRoomStereo);
+        StereoOffCommand stereoOffCommand = new StereoOffCommand(livingRoomStereo);
+
+        // 람다식은 메소드가 오직 한개일 때에만 사용할 수 있다.
+//        remoteControl.setCommand(0, livingRoomLight::on, livingRoomLight::off);
+//        remoteControl.setCommand(1, kitchenLight::on, kitchenLight::off);
+//        remoteControl.setCommand(2, garageDoor::up, garageDoor::down);
+        remoteControl.setCommand(3, stereoOnWithCDCommand, stereoOffCommand);
+
+        System.out.println(remoteControl);
+
+        for (int i = 0; i < 4; i++) {
+            remoteControl.onButtonWasPushed(i);
+            remoteControl.offButtonWasPushed(i);
+        }
+    }
+
+    private static void remoteControlWithUndo() {
+        RemoteControlWithUndo remoteControl = new RemoteControlWithUndo();
+
+        Light livingRoomLight = new Light("Living Room");
+
+        LightOnCommand livingRoomLightOnCommand = new LightOnCommand(livingRoomLight);
+        LightOffCommand livingRoomLightOffCommand = new LightOffCommand(livingRoomLight);
+
+        remoteControl.setCommand(0, livingRoomLightOnCommand, livingRoomLightOffCommand);
+
+        remoteControl.onButtonWasPushed(0);
+        remoteControl.offButtonWasPushed(0);
+        System.out.println(remoteControl);
+
+        remoteControl.undoButtonWasPushed();
+
+        remoteControl.offButtonWasPushed(0);
+        remoteControl.onButtonWasPushed(0);
+        System.out.println(remoteControl);
+    }
+}

src/command/command/Command.java

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+package command.command;
+
+/**
+ * 커맨드 객체는 모두 같은 인터페이스(Command)를 구현해야 한다.
+ * 해당 인터페이스는 메소드가 하나뿐이다.
+ */
+public interface Command {
+    void execute();
+
+    void undo();
+}

src/command/command/impl/GarageDoorDownCommand.java

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+package command.command.impl;
+
+import command.command.Command;
+import command.receiver.GarageDoor;
+
+public class GarageDoorDownCommand implements Command {
+    private final GarageDoor garageDoor;
+
+    public GarageDoorDownCommand(GarageDoor garageDoor) {
+        this.garageDoor = garageDoor;
+    }
+
+    @Override
+    public void execute() {
+        garageDoor.down();
+    }
+
+    @Override
+    public void undo() {
+        garageDoor.up();
+    }
+}

src/command/command/impl/GarageDoorUpCommand.java

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+package command.command.impl;
+
+import command.command.Command;
+import command.receiver.GarageDoor;
+
+public class GarageDoorUpCommand implements Command {
+    private final GarageDoor garageDoor;
+
+    public GarageDoorUpCommand(GarageDoor garageDoor) {
+        this.garageDoor = garageDoor;
+    }
+
+    @Override
+    public void execute() {
+        garageDoor.up();
+    }
+
+    @Override
+    public void undo() {
+        garageDoor.down();
+    }
+}

src/command/command/impl/LightOffCommand.java

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+package command.command.impl;
+
+import command.command.Command;
+import command.receiver.Light;
+
+public class LightOffCommand implements Command {
+    private final Light light; // 리시버 객체
+
+    public LightOffCommand(Light light) {
+        this.light = light;
+    }
+
+    @Override
+    public void execute() {
+        light.off();
+    }
+
+    @Override
+    public void undo() {
+        light.on();
+    }
+}

src/command/command/impl/LightOnCommand.java

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+package command.command.impl;
+
+import command.command.Command;
+import command.receiver.Light;
+
+public class LightOnCommand implements Command {
+    private final Light light; // 리시버 객체
+
+    public LightOnCommand(Light light) {
+        this.light = light;
+    }
+
+    @Override
+    public void execute() {
+        light.on();
+    }
+
+    @Override
+    public void undo() {
+        light.off();
+    }
+}

src/command/command/impl/NoCommand.java

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+package command.command.impl;
+
+import command.command.Command;
+
+/**
+ * 일종의 null object
+ * null 처리 로직을 줄이고 싶을 때 활용한다.
+ * null object 를 일종의 디자인 패턴으로 분류하기도 한다.
+ */
+public class NoCommand implements Command {
+    @Override
+    public void execute() {
+
+    }
+
+    @Override
+    public void undo() {
+
+    }
+}

src/command/command/impl/StereoOffCommand.java

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+package command.command.impl;
+
+import command.command.Command;
+import command.receiver.Stereo;
+
+public class StereoOffCommand implements Command {
+    private final Stereo stereo;
+
+    public StereoOffCommand(Stereo stereo) {
+        this.stereo = stereo;
+    }
+
+    @Override
+    public void execute() {
+        stereo.off();
+    }
+
+    @Override
+    public void undo() {
+        stereo.on();
+        stereo.setCD();
+        stereo.setVolume(11);
+    }
+}

src/command/command/impl/StereoOnWithCDCommand.java

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+package command.command.impl;
+
+import command.command.Command;
+import command.receiver.Stereo;
+
+public class StereoOnWithCDCommand implements Command {
+    private final Stereo stereo;
+
+    public StereoOnWithCDCommand(Stereo stereo) {
+        this.stereo = stereo;
+    }
+
+    @Override
+    public void execute() {
+        stereo.on();
+        stereo.setCD();
+        stereo.setVolume(11);
+    }
+
+    @Override
+    public void undo() {
+        stereo.off();
+    }
+}

src/command/invoker/RemoteControl.java

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+package command.invoker;
+
+import command.command.Command;
+import command.command.impl.NoCommand;
+
+public class RemoteControl {
+    Command[] onCommands;
+    Command[] offCommands;
+
+    public RemoteControl() {
+        onCommands = new Command[7];
+        offCommands = new Command[7];
+
+        final NoCommand noCommand = new NoCommand(); // 빈 커맨드 객체
+        for (int i = 0; i < 7; i++) {
+            onCommands[i] = noCommand;
+            offCommands[i] = noCommand;
+        }
+    }
+
+    public void setCommand(int slot, Command onCommand, Command offCommand) {
+        onCommands[slot] = onCommand;
+        offCommands[slot] = offCommand;
+    }
+
+    public void onButtonWasPushed(int slot) {
+        onCommands[slot].execute();
+    }
+
+    public void offButtonWasPushed(int slot) {
+        offCommands[slot].execute();
+    }
+
+    @Override
+    public String toString() {
+        final StringBuilder stringBuilder = new StringBuilder();
+        stringBuilder.append("\n------- 리모컨 -------\n");
+        for (int i = 0; i < onCommands.length; i++) {
+            stringBuilder.append("[slot ")
+                    .append(i)
+                    .append("]")
+                    .append(onCommands[i].getClass().getName())
+                    .append("   ")
+                    .append(offCommands[i].getClass().getName())
+                    .append("\n");
+        }
+        return stringBuilder.toString();
+    }
+}