某灯具厂商欲生产一个灯具遥控器，该遥控器具有7个可编程的插槽，每个插槽都有开关灯具的开关，现采用Command（命令）模式实现该遥控器的软件部分。Command模式的类图如图6-1所示。
【Java代码】
class Light{
public Light（ ）{}
public Light(String name){/*代码省略*/}
public void on（ ）{/*代码省略*/}//开灯
public void off（ ）{/*代码省略*/}//关灯
//其余代码省略
}
（1）{
public void execute（ ）;
}
class LightOnCommand implements Command{//开灯命令
Light light;
public LightOnCommand(Light light){this.light=light;}
public void execute（ ）{（2）;}
}
class LightOffCommand implements Command{//关灯命令
Light light;
public LightOffCommand(Light light){this.light=light;}
public void execute（ ）{（3）;}
}
class RemoteControl{//遥控器
Command[]onCommands=new Command[7];
Command[]offCommands=new Command[7];
public RemoteControl（ ）{/*代码省略*/}
public void setCommand(int slot,Command onCommand,Command offCommand){
（4）=onCommand;
（5）=offCommand;
}
public void onButtonWasPushed(int slot){
（6）;
}
public void offlButtonWasPushed(int slot){
（7）;
}
}
class RemoteLoader{
public static void main(String[]args){
RemoteControl remoteControl=new RemoteControl（ ）;
Light livingRoomLight=new Light("Living Room");
Light kitchenLight=new Light("kitchen");
LightOnCommand livingRoomLightOn=new LightOnCommand(livingRoomLight);
LightOffCommand livingRoomLightOff=new LightOffCommand(livingRoomLight);
LightOnCommand kitchenLightOn=new LightOnCommand(kitchenLight);
LightOffCommand kitchenLightOff=new LightOffCommand(kitchenLight);
remoteControl.setCommand(0,livingRoomLightOn,livingRoomLightOff);
remoteControl.setCommand(1,kitchenLightOn,kitchenLightOff);
remoteControl.onButtonWasPushed(0);
remoteControl.offButtonWasPushed(0);
remoteControl.onButtonWasPushed(1);
remoteControl.offButtonWasPushed(1);
}
}
正确答案及解析
正确答案
解析
（1）interface Command
（2）light.on()
（3）light.off()
（4）onCommands[slot]
（5）offCommands[slot]
（6）onCommands[slot].execute()
（7）offCommands[slot].execute()
本题考察设计模式的实现，难度较小。根据类图和已有代码可写出空缺的代码.
（1）是Command接口的实现，应该填写interface Command；
（2）和（3）定义了开灯、关灯action，因此，分别填写（2）light->on()（3）light->off()；
（4）（5）分别设置“开灯”命令对象、“关灯”命令对象，因此分别填写（4）onCommands[slot]（5）offCommands[slot]；
（6）（7）分别完成对开灯、关灯命令对象的execute方法的调用，因此分别填写（6）onCommands[slot].execute()
（7）offCommands[slot].execute()。
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