What are the differences between Abstract Factory and Factory design patterns

Question

I know there are many posts out there about the differences between these two patterns  but there are a few things that I cannot find   From what I have been reading  I see that the factory method pattern allows you to define how to create a single concrete product but hiding the implementation from the client as they will see a generic product  My first question is about the abstract factory  Is its role to allow you to create families of concrete objects in  that can depend on what specific factory you use  rather than just a single concrete object  Does the abstract factory only return one very large object or many objects depending on what methods you call   My final two questions are about a single quote that I cannot fully understand that I have seen in numerous places      One difference between the two is that   with the Abstract Factory pattern  a   class delegates the responsibility of   object instantiation to another object   via composition whereas the Factory   Method pattern uses inheritance and   relies on a subclass to handle the   desired object instantiation    My understanding is that the factory method pattern has a Creator interface that will make the ConcreteCreator be in charge of knowing which ConcreteProduct to instantiate  Is this what it means by using inheritance to handle object instantiation   Now with regards to that quote  how exactly does the Abstract Factory pattern delegate the responsibility of object instantiation to another object via composition  What does this mean  It looks like the Abstract Factory pattern also uses inheritance to do the construction process as well in my eyes  but then again I am still learning about these patterns   Any help especially with the last question  would be greatly appreciated

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Factory Method relies on inheritance  Object creation is delegated to subclasses  which implement the factory method to create objects   Abstract Factory relies on object composition  object creation is implemented in methods exposed in the factory interface   High level diagram of Factory and Abstract factory pattern     For more information about the Factory method  refer this article   For more information about Abstract factory method  refer this article

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Understand the differences in the motivations       Suppose you   re building a tool where you   ve objects and a concrete implementation of the interrelations of the objects  Since you foresee variations in the objects  you   ve created an indirection by assigning the responsibility of creating variants of the objects to another object  we call it abstract factory   This abstraction finds strong benefit since you foresee future extensions needing variants of those objects       Another rather intriguing motivation in this line of thoughts is a case where every-or-none of the objects from the whole group will have a corresponding variant  Based on some conditions  either of the variants will be used and in each case all objects must be of same variant  This might be a bit counter intuitive to understand as we often tend think that - as long as the variants of an object follow a common uniform contract  interface in broader sense   the concrete implementation code should never break  The intriguing fact here is that  not always this is true especially when expected behavior cannot be modeled by a programming contract   A simple  borrowing the idea from GoF  is any GUI applications say a virtual monitor that emulates look-an-feel of MS or Mac or Fedora OS   s  Here  for example  when all widget objects such as window  button  etc  have MS variant except a scroll-bar that is derived from MAC variant  the purpose of the tool fails badly       These above cases form the fundamental need of Abstract Factory Pattern    On the other hand  imagine you   re writing a framework so that many people can built various tools  such as the one in above examples  using your framework  By the very idea of a framework  you don   t need to  albeit you could not use concrete objects in your logic  You rather put some high level contracts between various objects and how they interact  While you  as a framework developer  remain at a very abstract level  each builders of the tool is forced to follow your framework-constructs  However  they  the tool builders  have the freedom to decide what object to be built and how all the objects they create will interact  Unlike the previous case  of Abstract Factory Pattern   you  as framework creator  don   t need to work with concrete objects in this case  and rather can stay at the contract level of the objects  Furthermore  unlike the second part of the previous motivations  you or the tool-builders never have the situations of mixing objects from variants  Here  while framework code remains at contract level  every tool-builder is restricted  by the nature of the case itself  to using their own objects  Object creations in this case is delegated to each implementer and framework providers just provide uniform methods for creating and returning objects  Such methods are inevitable for framework developer to proceed with their code and has a special name called Factory method  Factory Method Pattern for the underlying pattern    Few Notes     If you   re familiar with    template method     then you   d see that factory methods are often invoked from  template methods in case of programs pertaining to any form of framework  By contrast  template methods of application-programs are often simple implementation of specific algorithm and void of factory-methods  Furthermore  for the completeness of the thoughts  using the framework  mentioned above   when a tool-builder is building a tool  inside each factory method  instead of creating a concrete object  he she may further delegate the responsibility to an abstract-factory object  provided the tool-builder foresees variations of the concrete objects for future extensions    Sample Code     Part of framework-code BoardGame       Board createBoard     factory method  Default implementation can be provided as well     Piece createPiece     factory method      startGame             template method          Board borad   createBoard            Piece piece   createPiece            initState board  piece              Part of Tool-builder code Ludo inherits  BoardGame        Board createBoard      overriding of factory method            Option A  return new LudoBoard     Lodu knows object creation            Option B  return LudoFactory createBoard     Lodu asks AbstractFacory                  Part of Tool-builder code Chess inherits  BoardGame       Board createBoard      overriding of factory method           return a Chess board

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Abstract Factory  A factory of factories  a factory that groups the individual but related dependent factories together without specifying their concrete classes  Abstract Factory Example  Factory  It provides a way to delegate the instantiation logic to child classes  Factory Pattern Example

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Allow me to put it precisely  Most of the answers have already explained  provided diagrams and examples as well  So my answer would just be a one-liner  My own words      An abstract factory pattern adds on the abstract layer over multiple factory method implementations  It means an abstract factory contains or composite one or more than one factory method pattern

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Abstract Factory is an interface for creating related products  but Factory Method is only one method  Abstract Factory can be implemented by multiple Factory Methods

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To make it very simple with minimum interface  amp  please focus    1    class FactoryProgram               static void Main                         object myType   Program MyFactory  byte                Console WriteLine myType GetType   Name                myType   Program MyFactory  float      3             Console WriteLine myType GetType   Name                Console ReadKey                       static object MyFactory string typeName                        object desiredType   null    1             switch  typeName                                case  byte   desiredType   new System Byte    break    2                 case  long   desiredType   new System Int64    break                  case  float   desiredType   new System Single    break                  default  throw new System NotImplementedException                              return desiredType                    Here important points  1  Factory  amp  AbstractFactory mechanisms must use inheritance  System Object-  byte  float       so if you have inheritance in program then Factory Abstract Factory would not be there most probably  is already there by design 2  Creator  MyFactory  knows about concrete type so returns concrete type object to caller Main   In abstract factory return type would be an Interface   interface IVehicle   string VehicleName   get  set      interface IVehicleFactory               IVehicle CreateSingleVehicle string vehicleType         class HondaFactory   IVehicleFactory               public IVehicle CreateSingleVehicle string vehicleType                        switch  vehicleType                                case  Sports   return new SportsBike                    case  Regular  return new RegularBike                    default  throw new ApplicationException string Format  Vehicle   0   cannot be created   vehicleType                                  class HeroFactory   IVehicleFactory               public IVehicle CreateSingleVehicle string vehicleType                        switch  vehicleType                                case  Sports    return new SportsBike                    case  Scooty   return new Scooty                    case  DarkHorse  return new DarkHorseBike                    default  throw new ApplicationException string Format  Vehicle   0   cannot be created   vehicleType                                   class RegularBike   IVehicle   public string VehicleName   get   return  Regular Bike- Name     set   VehicleName   value        class SportsBike   IVehicle   public string VehicleName   get   return  Sports Bike- Name     set   VehicleName   value        class RegularScooter   IVehicle   public string VehicleName   get   return  Regular Scooter- Name     set   VehicleName   value        class Scooty   IVehicle   public string VehicleName   get   return  Scooty- Name     set   VehicleName   value        class DarkHorseBike   IVehicle   public string VehicleName   get   return  DarkHorse Bike- Name     set   VehicleName   value         class Program       static void Main string   args                IVehicleFactory honda   new HondaFactory      1         RegularBike hondaRegularBike    RegularBike honda CreateSingleVehicle  Regular      2         SportsBike hondaSportsBike    SportsBike honda CreateSingleVehicle  Sports            Console WriteLine          Honda             hondaRegularBike VehicleName  hondaSportsBike VehicleName            IVehicleFactory hero   new HeroFactory            DarkHorseBike heroDarkHorseBike    DarkHorseBike hero CreateSingleVehicle  DarkHorse            SportsBike heroSportsBike    SportsBike hero CreateSingleVehicle  Sports            Scooty heroScooty    Scooty hero CreateSingleVehicle  Scooty            Console WriteLine          Hero             heroDarkHorseBike VehicleName   heroScooty VehicleName  heroSportsBike VehicleName            Console ReadKey              Important points  1  Requirement  Honda would create  Regular    Sports  but Hero would create  DarkHorse    Sports  and  Scooty   2  why two interfaces   One for manufacturer type IVehicleFactory  and another for product  factory IVehicle   other way to understand 2 interfaces is abstract factory is all about creating related objects 2  The catch is the IVehicleFactory s children returning and IVehicle instead of concrete in factory   so I get parent variable IVehicle   then I create actual concrete type by calling CreateSingleVehicle and then casting parent object to actual child object  What would happen if I do RegularBike heroRegularBike    RegularBike hero CreateSingleVehicle  Regular     you will get ApplicationException and that s why we need generic abstract factory which I would explain if required  Hope it helps from beginner to intermediate audience

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Let us put it clear that most of the time in production code  we use abstract factory pattern because class A is programmed with interface B   And A needs to create instances of B   So A has to have a factory object to produce instances of B  So A is not dependent on any concrete instance of B   Hope it helps

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I would favor Abstract Factory over Factory Method anytime  From Tom Dalling s example  great explanation btw  above  we can see that Abstract Factory is more composable in that all we need to do is passing a different Factory to the constructor  constructor dependency injection in use here   But Factory Method requires us to introduce a new class  more things to manage  and use subclassing  Always prefer composition over inheritance

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There are quite a few definitions out there  Basically  the three common way of describing factory pattern are  Simple Factory   Simple object creation method class based on a condition    Factory Method   The Factory Method design pattern using subclasses to provide the implementation    Abstract Factory   The Abstract Factory design pattern producing families of related or dependent objects without specifying their concrete classes   The below link was very useful - Factory Comparison - refactoring guru

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My first question is about the abstract factory  Is its role to allow you to create families of concrete objects in  that can depend on what specific factory you use  rather than just a single concrete object        Yes  The intent of Abstract Factory is      Provide an interface for creating families of related or dependent objects without specifying their concrete classes            Does the abstract factory only return one very large object or many objects depending on what methods you call       Ideally it should return one object per the method client is invoking          My understanding is that the factory method pattern has a Creator interface that will make the ConcreteCreator be in charge of knowing which ConcreteProduct to instantiate  Is this what it means by using inheritance to handle object instantiation       Yes  Factory method uses inheritance           Abstract Factory pattern delegate the responsibility of object instantiation to another object via composition  What does this mean       AbstractFactory defines a FactoryMethod and ConcreteFactory is responsible for building a ConcreteProduct  Just follow through the code example in this article   You can find more details in related SE posts   What is the basic difference between the Factory and Abstract Factory Patterns   Design Patterns  Factory vs Factory method vs Abstract Factory

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Abstract factory creates a base class with abstract methods defining methods for the objects that should be created  Each factory class which derives the base class can create their own implementation of each object type     Factory method is just a simple method used to create objects in a class  It s usually added in the aggregate root  The Order class has a method called CreateOrderLine     Abstract factory  In the example below we design an interface so that we can decouple queue creation from a messaging system and can therefore create implementations for different queue systems without having to change the code base   interface IMessageQueueFactory     IMessageQueue CreateOutboundQueue string name     IMessageQueue CreateReplyQueue string name      public class AzureServiceBusQueueFactory   IMessageQueueFactory         IMessageQueue CreateOutboundQueue string name                       init queue            return new AzureMessageQueue                           IMessageQueue CreateReplyQueue string name                       init response queue            return new AzureResponseMessageQueue                        public class MsmqFactory   IMessageQueueFactory         IMessageQueue CreateOutboundQueue string name                       init queue            return new MsmqMessageQueue                           IMessageQueue CreateReplyQueue string name                       init response queue            return new MsmqResponseMessageQueue                        Factory method  The problem in HTTP servers is that we always need an response for every request   public interface IHttpRequest             all other methods         IHttpResponse CreateResponse int httpStatusCode       Without the factory method  the HTTP server users  i e  programmers  would be forced to use implementation specific classes which defeat the purpose of the IHttpRequest interface   Therefore we introduce the factory method so that the creation of the response class also is abstracted away   Summary  The difference is that the intended purpose of the class containing a factory method is not to create objects  while an abstract factory should only be used to create objects   One should take care when using factory methods since it s easy to break the LSP  Liskov Substitution principle  when creating objects

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abstract factory design pattern with realtime example  what is an abstract factory design pattern   It is similar to the factory method design pattern  we need to use this pattern when we have multiple factories  there will be a grouping of factories defined in this pattern  factory method pattern is a subset of abstract factory design pattern  They have the same advantages as factory patterns  abstract factory relies on object composition whereas the factory method deals with inheritance  factory design pattern in java with a realtime example  what is the factory design pattern  it is mostly used design in object-oriented programming  It is one of the creational patterns  it is all about creating instances  Clients will create the object without exposed to object creational logic  it is widely used in different frameworks ex  the spring framework  we use this pattern when the class doesn   t know the objects of another it must create  Realtime example  when our car breaks down on the road  We need to inform the repairman about what type of vehicle we are using so that repairman will carry tools to fix the repair  as per our input  the repairman will fix the issue and make it ready for us to travel again  There are a few built-in methods that use these patterns  example getInstance   method in JavaUtilcalendar class  With help of getInstance    we can get objects whenever we execute this method  Javautilcalendar   getInstance   is method return object  https   trendydevx com factory-design-pattern-in-java-with-realtime-example

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The main difference between Abstract Factory and Factory Method is that Abstract Factory is implemented by Composition  but Factory Method is implemented by Inheritance   Yes  you read that correctly  the main difference between these two patterns is the old composition vs inheritance debate   UML diagrams can be found in the  GoF  book  I want to provide code examples  because I think combining the examples from the top two answers in this thread will give a better demonstration than either answer alone  Additionally  I have used terminology from the book in class and method names   Abstract Factory   The most important point to grasp here is that the abstract factory is injected into the client  This is why we say that Abstract Factory is implemented by Composition  Often  a dependency injection framework would perform that task  but a framework is not required for DI  The second critical point is that the concrete factories here are not Factory Method implementations  Example code for Factory Method is shown further below  And finally  the third point to note is the relationship between the products  in this case the outbound and reply queues  One concrete factory produces Azure queues  the other MSMQ  The GoF refers to this product relationship as a  family  and it s important to be aware that family in this case does not mean class hierarchy    public class Client       private final AbstractFactory MessageQueue factory       public Client AbstractFactory MessageQueue factory               The factory creates message queues either for Azure or MSMQ             The client does not know which technology is used          this factory   factory             public void sendMessage               The client doesn t know whether the OutboundQueue is Azure or MSMQ          OutboundQueue out   factory createProductA            out sendMessage  Hello Abstract Factory                public String receiveMessage               The client doesn t know whether the ReplyQueue is Azure or MSMQ          ReplyQueue in   factory createProductB            return in receiveMessage             public interface AbstractFactory MessageQueue       OutboundQueue createProductA        ReplyQueue createProductB       public class ConcreteFactory Azure implements AbstractFactory MessageQueue        Override     public OutboundQueue createProductA             return new AzureMessageQueue                Override     public ReplyQueue createProductB             return new AzureResponseMessageQueue             public class ConcreteFactory Msmq implements AbstractFactory MessageQueue        Override     public OutboundQueue createProductA             return new MsmqMessageQueue                Override     public ReplyQueue createProductB             return new MsmqResponseMessageQueue              Factory Method   The most important point to grasp here is that the ConcreteCreator is the client  In other words  the client is a subclass whose parent defines the factoryMethod    This is why we say that Factory Method is implemented by Inheritance  The second critical point is to remember that the Factory Method Pattern is nothing more than a specialization of the Template Method Pattern  The two patterns share an identical structure  They only differ in purpose  Factory Method is creational  it builds something  whereas Template Method is behavioral  it computes something   And finally  the third point to note is that the Creator  parent  class invokes its own factoryMethod    If we remove anOperation   from the parent class  leaving only a single method behind  it is no longer the Factory Method pattern  In other words  Factory Method cannot be implemented with less than two methods in the parent class  and one must invoke the other    public abstract class Creator       public void anOperation             Product p   factoryMethod            p whatever               protected abstract Product factoryMethod       public class ConcreteCreator extends Creator        Override     protected Product factoryMethod             return new ConcreteProduct              Misc   amp  Sundry Factory Patterns  Be aware that although the GoF define two different Factory patterns  these are not the only Factory patterns in existence  They are not even necessarily the most commonly used Factory patterns  A famous third example is Josh Bloch s Static Factory Pattern from Effective Java  The Head First Design Patterns book includes yet another pattern they call Simple Factory   Don t fall into the trap of assuming every Factory pattern must match one from the GoF

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Consider this example for easy understanding    What does telecommunication companies provide  Broadband  phone line and mobile for instance and you re asked to create an application to offer their products to their customers   Generally what you d do here is  creating the products i e broadband  phone line and mobile are through your Factory Method where you know what properties you have for those products and it s pretty straightforward   Now  the company wants to offer their customer a bundle of their products i e broadband  phone line  and mobile altogether  and here comes the Abstract Factory to play   Abstract Factory is  in other words  are the composition of other factories who are responsible for creating their own products and Abstract Factory knows how to place these products in more meaningful in respect of its own responsibilities   In this case  the BundleFactory is the Abstract Factory  BroadbandFactory  PhonelineFactory and MobileFactory are the Factory  To simplify more  these Factories will have Factory Method to initialise the individual products   Se the code sample below   public class BroadbandFactory   IFactory       public static Broadband CreateStandardInstance                broadband product creation logic goes here          public class PhonelineFactory   IFactory       public static Phoneline CreateStandardInstance                phoneline product creation logic goes here          public class MobileFactory   IFactory       public static Mobile CreateStandardInstance                mobile product creation logic goes here          public class BundleFactory   IAbstractFactory        public static Bundle CreateBundle             broadband   BroadbandFactory CreateStandardInstance            phoneline   PhonelineFactory CreateStandardInstance            mobile   MobileFactory CreateStandardInstance             applySomeDiscountOrWhatever broadband  phoneline  mobile              private static void applySomeDiscountOrWhatever Broadband bb  Phoneline pl  Mobile m               some logic here            maybe manange some variables and invoke some other methods services etc            Hope this helps

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Real Life Example   Easy to remember   Factory  Imagine you are constructing a house and you approach a carpenter for a door  You give the measurement for the door and your requirements  and he will construct a door for you  In this case  the carpenter is a factory of doors  Your specifications are inputs for the factory  and the door is the output or product from the factory   Abstract Factory  Now  consider the same example of the door  You can go to a carpenter  or you can go to a plastic door shop or a PVC shop  All of them are door factories  Based on the situation  you decide what kind of factory you need to approach  This is like an Abstract Factory   I have explained here both Factory method pattern and abstract factory pattern beginning with not using them explaining issues and then solving issues by using the above patterns https   github com vikramnagineni Design-Patterns tree master

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The Difference Between The Two The main difference between a  quot factory method quot  and an  quot abstract factory quot  is that the factory method is a method  and an abstract factory is an object  I think a lot of people get these two terms confused  and start using them interchangeably  I remember that I had a hard time finding exactly what the difference was when I learnt them  Because the factory method is just a method  it can be overridden in a subclass  hence the second half of your quote       the Factory Method pattern uses inheritance and relies on a subclass to handle the desired object instantiation   The quote assumes that an object is calling its own factory method here  Therefore the only thing that could change the return value would be a subclass  The abstract factory is an object that has multiple factory methods on it  Looking at the first half of your quote       with the Abstract Factory pattern  a class delegates the responsibility of object instantiation to another object via composition      What they re saying is that there is an object A  who wants to make a Foo object  Instead of making the Foo object itself  e g   with a factory method   it s going to get a different object  the abstract factory  to create the Foo object  Code Examples To show you the difference  here is a factory method in use  class A       public void doSomething             Foo f   makeFoo            f whatever                  protected Foo makeFoo             return new RegularFoo             class B extends A       protected Foo makeFoo               subclass is overriding the factory method            to return something different         return new SpecialFoo             And here is an abstract factory in use  class A       private Factory factory       public A Factory factory            this factory   factory             public void doSomething               The concrete class of  quot f quot  depends on the concrete class           of the factory passed into the constructor  If you provide a           different factory  you get a different Foo object          Foo f   factory makeFoo            f whatever             interface Factory       Foo makeFoo        Bar makeBar        Aycufcn makeAmbiguousYetCommonlyUsedFakeClassName         need to make concrete factories that implement the  quot Factory quot  interface here

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A lot of the previous answers do not provide code comparisons between Abstract Factory and Factory Method pattern  The following is my attempt at explaining it via Java  I hope it helps someone in need of a simple explanation   As GoF aptly says   Abstract Factory provides an interface for creating families of related or dependent objects without specifying their concrete classes   public class Client       public static void main String   args            ZooFactory zooFactory   new HerbivoreZooFactory            Animal animal1   zooFactory animal1            Animal animal2   zooFactory animal2            animal1 sound            animal2 sound             System out println             AnimalFactory animalFactory   new CowAnimalFactory            Animal animal   animalFactory createAnimal            animal sound              public interface Animal       public void sound       public class Cow implements Animal         Override     public void sound             System out println  quot Cow moos quot             public class Deer implements Animal         Override     public void sound             System out println  quot Deer grunts quot              public class Hyena implements Animal         Override     public void sound             System out println  quot Hyena java quot              public class Lion implements Animal         Override     public void sound             System out println  quot Lion roars quot               public interface ZooFactory       Animal animal1         Animal animal2       public class CarnivoreZooFactory implements ZooFactory         Override     public Animal animal1             return new Lion                Override     public Animal animal2             return new Hyena              public class HerbivoreZooFactory implements ZooFactory         Override     public Animal animal1             return new Cow                Override     public Animal animal2             return new Deer               public interface AnimalFactory       public Animal createAnimal       public class CowAnimalFactory implements AnimalFactory         Override     public Animal createAnimal             return new Cow              public class DeerAnimalFactory implements AnimalFactory         Override     public Animal createAnimal             return new Deer              public class HyenaAnimalFactory implements AnimalFactory         Override     public Animal createAnimal             return new Hyena              public class LionAnimalFactory implements AnimalFactory         Override     public Animal createAnimal             return new Lion

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Difference between AbstractFactory and Factory design patterns are as follows    Factory Method is used to create one product only but Abstract Factory is about creating families of related or dependent products  Factory Method pattern exposes a method to the client for creating the object whereas in the case of Abstract Factory they expose a family of related objects which may consist of these Factory methods  Factory Method pattern hides the construction of a single object whereas Abstract Factory hides the construction of a family of related objects  Abstract factories are usually implemented using  a set of  factory methods  Abstract Factory pattern uses composition to delegate the responsibility of creating an object to another class while Factory Method design pattern uses inheritance and relies on a derived class or subclass to create an object  The idea behind the Factory Method pattern is that it allows for the case where a client doesn t know what concrete classes it will be required to create at runtime  but just wants to get a class that will do the job while Abstract Factory  pattern is best utilized when your system has to create multiple families of products or you want to provide a library of products without exposing the implementation details     Factory Method Pattern Implementation    Abstract Factory Pattern Implementation

[factory-pattern] What are the differences between Abstract Factory and Factory design patterns?

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