Factory method Pattern of design pattern

Factory method Mode

Defines an interface for creating objects, letting subclasses decide which class to instantiate. The factory method defers the instantiation of a class to a subclass.

Operation class

 PackageCom.hml.factory.method; Public Abstract classOperation {Private intNumbera; Private intNumberb;  Public intGetnumbera () {returnNumbera; }     Public voidSetnumbera (intNumbera) {         This. Numbera =Numbera; }     Public intGetnumberb () {returnNumberb; }     Public voidSetnumberb (intNumberb) {         This. Numberb =Numberb; }     Public Abstract intGetResult ();}

Addoperation class

 Package Com.hml.factory.method;  Public class extends Operation {    publicint  getresult () {        return Getnumbera () + Getnumberb ();    }}

Suboperation class

 Package Com.hml.factory.method;  Public class extends Operation {    publicint  getresult () {        return Getnumbera ()- Getnumberb ();    }}

Ifactory class

 Package Com.hml.factory.method;  Public Interface ifactory {    public  Operation CreateOperation ();}

Addoperationfacotry class

 Package Com.hml.factory.method;  Public class Implements ifactory {    public  Operation CreateOperation () {        returnnew addoperation ();    }}

 Package Com.hml.factory.method;  Public class Implements ifactory {    public  Operation CreateOperation () {        returnnew suboperation ();    }}

Class diagram

When the factory method pattern is implemented, the client needs to decide which factory to instantiate to implement the Operation class, the problem of choosing judgment is still there, that is, the factory method moves the internal logic judgment of the simple factory to the client code, wants to add the function, it is to modify the factory class, and now is to modify the client code.

Factory method Pattern of design pattern