6. Command mode

Command pattern definition: Encapsulates a request into an object so that different requests, queues, or logs are used to parameterize other objects.

• The command mode decouples the requesting object (Remotecontrol remote control Class) from the object executing the request (illumination Class);
• Communicate between the decoupled objects by command object (for example, the light class Lightcommand and the Turn off command);
• The caller makes a request by invoking the command execute (), and execute () invokes the actual performer;
• The caller can receive command arguments, even dynamically at run time (dynamically binds the command to the caller's remote, and the caller's remote is programmed for the interface);
• Command can support undo undo operation, on the caller (remote control) can record the last executed command, call undo undo the last command;
• Command mode enables logging and queuing systems:

Log system: Each command executed can be logged to the log system, when the system crashes or freezes, the system can be re-executed according to the command of the log system to restore; Queue system: Work queue, the actual work object and the caller decoupling, such as: thread pool, etc.; Defining a command interface: a way to standardize the implementation of each command

 Public Interface Command {    void  execute ();     void undo ();}

Define LAMP class: Under the light includes open and close two commands.

 Public class Light {    private  String name;      Public Light (String name) {        this. Name = name;    }       Public void On () {        System.out.println ("open Light");    }      Public void off () {        System.out.println ("Off Light");}    }

Define the Light command class: The light-on and off-lights command for encapsulating lights.

 Public class Implements Command {    private light light ;      Public Lightcommand (light) {        this. Light = light ;    }    @Override    publicvoid  execute () {        light.on ();    }    @Override    publicvoid  undo () {        light.off ();    }}

Defines the Nocommand command for numeric keys that do not have commands on the remote.

 Public class Implements Command {    public  Nocommand () {    }    @Override    publicvoid  Execute () {        System.out.println ("no command opened");    }    @Override    publicvoid  undo () {        System.out.println ("no Close Command") ;    }}

Defines the remote control class: Defines an array of commands to be stored, and two commands for opening and closing a user;

 Public classRemotecontrol {command[] commands;  PublicRemotecontrol () {commands=NewCommand[10];  for(inti=0;i<10;i++) {Commands[i]=NewNocommand (); }    }     Public voidSetcommands (intSlot,command OnCommand) {Commands[slot]=OnCommand; }     Public voidOnbutton (intslot)    {Commands[slot].execute (); }     Public voidOffbutton (intslot)    {Commands[slot].undo (); }}

Test class:

 Public classTest { Public Static voidMain (string[] args) { light light=NewLight ("Electric bulb"); Lightcommand Lightcommand=NewLightcommand (light); Remotecontrol Control=NewRemotecontrol (); Control.setcommands (0, Lightcommand); Control.onbutton (0); Control.offbutton (0); Control.onbutton (1); Control.offbutton (1); }} results: Turn off the lights without opening the command without closing the command

6. Command mode