命令模式应用场景

　　比如有个这样的场景，一个控制器，上面有很多对按钮，一对按钮包括开和关，然后这个可以将一些电器插在这个上面，然后就可以通过这个控制器来进行控制相应的电器。如果以后类似于需要模拟这种场景，你可以参考下这种模式。

命令模式使用步骤

　　1.定义一个命令接口，所有命令都需要是现在这个接口，其主要方法有execute，即执行命令。

public interface Command {    public void execute();}

　　2.定义一个电器接口，所有电器实现这个接口，方法主要是有on和off，即打开和关闭。

public interface Device {    public void on();    public void off();}

　　3.编写一些接口实现类，如灯泡、收音机等及其相关命令实现类

//Light.javapublic class Light implements Device {    private String deviceName;    public Light() {        deviceName = "Light";    }    @Override    public void on() {
            System.out.println(deviceName + " is twinkling");    }    @Override    public void off() {
            System.out.println(deviceName + " is off");    }}//Radio.javapublic class Radio implements Device {    private String deviceName;            public Radio() {        deviceName = "radio";    }        @Override    public void on() {        System.out.println(deviceName + "is working");    }    @Override    public void off() {            System.out.println(deviceName + "is over");    }}//CommandOn.javapublic class CommandOn implements Command {    private Device device;    public CommandOn(Device device) {        this.device = device;    }    @Override    public void execute() {        device.on();    }}//CommandOff.javapublic class CommandOff implements Command {        private Device device;    public CommandOff(Device device) {        this.device = device;    }        @Override    public void execute() {        device.off();    }}

　　4.编写控制器

public class RemoteController {    private Command[] commandsOn;    private Command[] commandsOff;    public RemoteController() {        commandsOn = new Command[7];        commandsOff = new Command[7];    }    public void setCommand(int index, Command on, Command off) {        commandsOn[index] = on;        commandsOff[index] = off;    }    public void onButton(int index) {        if (commandsOn[index] != null)            commandsOn[index].execute();    }    public void offButton(int index) {        if (commandsOff[index] != null)            commandsOff[index].execute();    }}

　　测试代码

public class Test {    public static void main(String[] args) {        RemoteController remoteController = new RemoteController();        Light light = new Light();        Radio radio = new Radio();        remoteController.setCommand(0, new CommandOn(light), new CommandOff(light));        remoteController.onButton(0);        remoteController.offButton(0);        remoteController.setCommand(0, new CommandOn(radio), new CommandOff(radio));        remoteController.onButton(0);        remoteController.offButton(0);    }}

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