命令模式定义：将“请求”封装成对象，以便使用不同的请求、队列或者日志来参数化其他对象。命令模式也支持可撤销的操作。
类图：
适用设计方案举例：实现一种遥控器，该遥控器具有七个可编程的插槽（每个都可以指定到一个不同的家电装置），每个插槽都有对应的开关按钮。这个遥控器还具备一个整体的撤销按钮。另外，多家厂商已经开发了一组Java类，例如电灯、风扇、热水器、音响设备和其他类似的可控制装置。遥控器如下图所示：
实现Code：
(1) 如下设备相关的Java类由厂商提供：
1 //CeilingFan.java
2 package RemoteControl.device;
3
4 public class CeilingFan {
5 String name;
6 public CeilingFan(String str)
7 {
8 name = str;
9 }
10
11 public void on()
12 {
13 System.out.println(name + "CeilingFan On");
14 }
15
16 public void off()
17 {
18 System.out.println(name + "CeilingFan Off");
19 }
20 }
1 //GarageDoor.java
2 package RemoteControl.device;
3
4 public class GarageDoor {
5 String name;
6 public GarageDoor(String str)
7 {
8 name = str;
9 }
10
11 public void up()
12 {
13 System.out.println(name + "GarageDoor On");
14 }
15
16 public void down()
17 {
18 System.out.println(name + "GarageDoor Off");
19 }
20 }
1 //Light.java
2 package RemoteControl.device;
3
4 public class Light {
5 String name;
6 public Light(String str)
7 {
8 name = str;
9 }
10
11 public void on()
12 {
13 System.out.println(name + "Light On");
14 }
15
16 public void off()
17 {
18 System.out.println(name + "Light Off");
19 }
20 }
1 //Stereo.java
2 package RemoteControl.device;
3
4 public class Stereo {
5 String name;
6 public Stereo(String str)
7 {
8 name = str;
9 }
10
11 public void on()
12 {
13 System.out.println(name + "Stereo On");
14 }
15
16 public void off()
17 {
18 System.out.println(name + "Stereo Off");
19 }
20
21 public void setCD()
22 {
23 System.out.println(name + "Stereo setCD");
24 }
25
26 public void setVolume(int num)
27 {
28 System.out.println(name + "Stereo setVolume:" + num);
29 }
30 }
(2) 将厂商提供的设备Java类库(即receiver)封装到Command类里面：
1 //CeilingFanOffCommand.java
2 package RemoteControl.Command;
3
4 import RemoteControl.device.CeilingFan;
5
6 public class CeilingFanOffCommand implements Command{
7 CeilingFan cf;
8
9 public CeilingFanOffCommand(CeilingFan cf)
10 {
11 this.cf = cf;
12 }
13
14 @Override
15 public void execute()
16 {
17 cf.off();
18 }
19
20 @Override
21 public void undo() {
22 cf.on();
23 }
24
25 }
1 //CeilingFanOnCommand.java
2 package RemoteControl.Command;
3
4 import RemoteControl.device.CeilingFan;
5
6
7 public class CeilingFanOnCommand implements Command{
8 CeilingFan cf;
9
10 public CeilingFanOnCommand(CeilingFan cf)
11 {
12 this.cf = cf;
13 }
14
15 @Override
16 public void execute()
17 {
18 cf.on();
19 }
20
21 @Override
22 public void undo() {
23 cf.off();
24 }
25 }
1 //Command.java
2 package RemoteControl.Command;
3
4 public interface Command {
5 public void execute();
6 public void undo();
7 }
1 //GarageDoorDownCommand.java
2 package RemoteControl.Command;
3
4 import RemoteControl.device.GarageDoor;
5
6 public class GarageDoorDownCommand implements Command {
7 GarageDoor gd;
8
9 public GarageDoorDownCommand(GarageDoor gd)
10 {
11 this.gd = gd;
12 }
13
14 @Override
15 public void execute()
16 {
17 gd.down();
18 }
19
20 @Override
21 public void undo() {
22 gd.up();
23 }
24 }
1 //GarageDoorUpCommand.java
2 package RemoteControl.Command;
3
4 import RemoteControl.device.GarageDoor;
5
6 public class GarageDoorUpCommand implements Command {
7 GarageDoor gd;
8
9 public GarageDoorUpCommand(GarageDoor gd)
10 {
11 this.gd = gd;
12 }
13
14 @Override
15 public void execute()
16 {
17 gd.up();
18 }
19
20 @Override
21 public void undo() {
22 gd.down();
23 }
24 }
1 //LightOffCommand.java
2 package RemoteControl.Command;
3
4 import RemoteControl.device.Light;
5
6 public class LightOffCommand implements Command {
7 Light light;
8
9 public LightOffCommand(Light light)
10 {
11 this.light = light;
12 }
13
14 @Override
15 public void execute()
16 {
17 light.off();
18 }
19
20 @Override
21 public void undo() {
22 light.on();
23 }
24 }
1 //LightOnCommand.java
2 package RemoteControl.Command;
3
4 import RemoteControl.device.Light;
5
6 public class LightOnCommand implements Command {
7
8 Light light;
9
10 public LightOnCommand(Light light)
11 {
12 this.light = light;
13 }
14
15 @Override
16 public void execute()
17 {
18 light.on();
19 }
20
21 @Override
22 public void undo() {
23 light.off();
24 }
25 }
1 //NoCommand.java
2 package RemoteControl.Command;
3
4 public class NoCommand implements Command{
5 public void execute()
6 {}
7
8 public void undo()
9 {}
10 }
1 //StereoOffCommand.java
2 package RemoteControl.Command;
3
4 import RemoteControl.device.Stereo;
5
6 public class StereoOffCommand implements Command {
7 Stereo stereo;
8
9 public StereoOffCommand(Stereo stereo)
10 {
11 this.stereo = stereo;
12 }
13
14 public void execute()
15 {
16 stereo.off();
17 }
18
19 @Override
20 public void undo() {
21 stereo.on();
22 }
23 }
1 //StereoOnWithCDCommand.java
2 package RemoteControl.Command;
3
4 import RemoteControl.device.Stereo;
5
6 public class StereoOnWithCDCommand implements Command {
7 Stereo stereo;
8
9 public StereoOnWithCDCommand(Stereo stereo)
10 {
11 this.stereo = stereo;
12 }
13
14 public void execute()
15 {
16 stereo.on();
17 stereo.setCD();
18 stereo.setVolume(11);
19 }
20
21 @Override
22 public void undo() {
23 stereo.off();
24 }
25 }
(3) 实现Invoker类：
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