6、命令模式

public interface Command {
    void execute();
    void undo();
}

public class Light {
    private String name;

    public Light(String name) {
        this.name = name;
    }

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

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

public class LightCommand implements Command {
    private Light light;

    public LightCommand(Light light){
        this.light = light;
    }

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

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

public class NoCommand implements Command {

    public NoCommand(){

    }

    @Override
    public void execute(){
        System.out.println("没有打开命令");
    }

    @Override
    public void undo(){
        System.out.println("没有关闭命令");
    }
}

public class RemoteControl {
    Command[] commands;

    public RemoteControl() {
        commands = new Command[10];
        for(int i=0;i<10;i++) {
            commands[i] = new NoCommand();
        }
    }
    public void setCommands(int slot,Command onCommand) {
        commands[slot] = onCommand;
    }
    public void onButton(int slot) {
        commands[slot].execute();
    }
    public void offButton(int slot) {
        commands[slot].undo();
    }
}

public class Test {
    public static void main(String[] args) {
        Light light = new Light("电灯");
        LightCommand lightCommand = new LightCommand(light);
        RemoteControl control = new RemoteControl();
        control.setCommands(0,lightCommand);
        control.onButton(0);
        control.offButton(0);
        control.onButton(1);
        control.offButton(1);
    }
}
执行结果：
开灯
关灯
没有打开命令
没有关闭命令