命令模式

將請求封裝成物件,可將此物件參數化,可用於操作日誌.佇列.還原等行為

主要分為

• Invoker
  1. 只負責執行invoke(),不關心物件及細節
  2. 可在此放進還原或是其他動作
• Receiver
  1. 請求所有細節在此決定(Ex. TV 有 on(), off() )
• Command
  1. 相關動作execute()的實作

public class Invoker {
    List<Command> commands = new LinkedList<>();

    public void addCommand(Command command){
        commands.add(command);
    }

    public void invoke(){
        for (Command command : commands) {
            command.execute();
        }
    }
}

public class TV {
    private String location = "";

    public TV(String location) {
        this.location = location;
    }

    public void on(){
        System.out.println(location + " TV is on");
    }

    public void off(){
        System.out.println(location + " TV is off");
    }

}

public interface Command {
    public void execute();
}

public class TVOnCommand implements Command {
   TV tv;

   public TVOnCommand(TV tv) {
      this.tv = tv;
   }

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

public class TVOffCommand implements Command {
   TV tv;

   public TVOffCommand(TV tv) {
      this.tv = tv;
   }

   @Override
   public void execute() {
      tv.off();
   }
}

public class Test {
   public static void main(String[] args) {
      Invoker invoker = new Invoker();
      TV tv = new TV("Living Room");
      TVOnCommand tvOnCommand = new TVOnCommand(tv);
      TVOffCommand tvOffCommand = new TVOffCommand(tv);
      invoker.addCommand(tvOnCommand);
      invoker.addCommand(tvOffCommand);
      invoker.invoke();

   }
}

Result:

Living Room TV is on
Living Room TV is off