Design pattern appearance (facade) mode (note)

The appearance mode (facade) provides a consistent interface for a set of interfaces in a subsystem that defines a high-level interface that makes this subsystem easier to use.
The appearance pattern perfectly embodies the thought that relies on the reversal principle and the Dimitri rule, so it is one of the more common design patterns.
The appearance mode structure diagram is as follows:

Define three subsystem classes

 Public classSubsystemone { Public void MethodOne() {System. out. println ("Subsystem Method 1"); }} Public classSubsystemtwo { Public void Methodtwo() {System. out. println ("Subsystem Method 2"); }} Public classSubsystemthree { Public void Methodthree() {System. out. println ("Subsystem Method 3"); }}

Define a skin facade class

public      Class  facade {private  subsystemone one; private     Subsystemtwo; private     Subsystemthree three; public  facade         () {One =new  subsystemone ();        Two=new  subsystemtwo ();    Three=new  subsystemthree (); } public  void          MethodA  () {one.methodone ();    Three.methodthree (); } public  void          MethodB  () {one.methodone ();    Two.methodtwo (); }}

Client code

publicstaticvoidmain(String[] args) {        Facade facade=new Facade();        facade.methodA();        facade.methodB();}

Due to the role of the facade class, the client can not know the existence of three subsystems at all

Design pattern appearance (facade) mode (note)