What is the difference between Builder Design pattern and Factory Design pattern

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What is the difference between the Builder design pattern and the Factory design pattern    Which one is more advantageous and why     How do I represent my findings as a graph if I want to test and compare contrast these patterns

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Both patterns come for the same necessity: Hide from some client code the construction logic of a complex object. But what makes "complex" (or, sometimes, complicate) an object? Mainly, it's due to dependencies, or rather the state of an object composed by more partial states. You can inject dependencies by constructor to set the initial object state, but an object may require a lot of them, some will be in a default initial state (just because we should have learned that set a default dependency to null is not the cleanest way) and some other set to a state driven by some condition. Moreover, there are object properties that are some kind of "oblivious dependencies" but also they can assume optional states.

there are two well known ways to dominate that complexity:

Composition/aggregation: Construct an object, construct its dependent objects, then wire together. Here, a builder can make transparent and flexible the process that determines the rules that lead the construction of component.
Polymorphism: Construction rules are declared directly into subtype definition, so you have a set of rules for each subtype and some condition decides which one among these set of rules apply to construct the object. A factory fits perfectly in this scenario.

Nothing prevents to mix these two approaches. A family of product could abstract object creation done with a builder, a builder could use factories to determine which component object instantiate.

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------------------------------------------------------------------- ---------------------------------------------------                                 Builder                                                     Factory                         ------------------------------------------------------------------- ---------------------------------------------------    Return only single instance to handle complex object construction   Retrun various instances on multiple constructors     No interface required                                               Interface driven                                      Inner classes is involved  to avoid telescopic constructors         Subclasses are involved                              ------------------------------------------------------------------- ---------------------------------------------------      Telescoping Constructor Pattern    Analogy        Factory  Consider a restaurant  The creation of  today s meal  is a factory pattern  because you tell the kitchen  get me today s meal  and the kitchen  factory  decides what object to generate  based on hidden criteria  Builder  The builder appears if you order a custom pizza  In this case  the waiter tells the chef  builder   I need a pizza  add cheese  onions and bacon to it   Thus  the builder exposes the attributes the generated object should have  but hides how to set them    Courtesy

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The Factory pattern can almost be seen as a simplified version of the Builder pattern   In the Factory pattern  the factory is in charge of creating various subtypes of an object depending on the needs   The user of a factory method doesn t need to know the exact subtype of that object  An example of a factory method createCar might return a Ford or a Honda typed object   In the Builder pattern  different subtypes are also created by a builder method  but the composition of the objects might differ within the same subclass   To continue the car example you might have a createCar builder method which creates a Honda-typed object with a 4 cylinder engine  or a Honda-typed object with 6 cylinders  The builder pattern allows for this finer granularity   Diagrams of both the Builder pattern and the Factory method pattern are available on Wikipedia

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Abstract Factory  amp  Builder pattern are both Creational patterns but with different intent   Abstract Factory Pattern emphasizes object creation for families of related objects where    Each family is a set of classes derived from a common base class Interface  Each object is returned immediately as a result of one call    Builder pattern focuses on constructing a complex object step by step   It decouples the representation from the process of constructing the complex object  so that the same construction process can be used for different representations    Builder object encapsulates configuration of the complex object  Director object knows the protocol of using the Builder  where the protocol defines all logical steps required to build the complex object

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Factory pattern creates a concrete implementation of a class at runtime  i e its main intention is to use polymorphism to allow subclasses decide which class to instantiate  This means at compile time we dont know the exact class that will be created  while Builder pattern is mainly concerned with solving the problem of telescoping constructors antipattern  which arises due to a large number of optional fields of a class  In builder pattern there is no notion of polymorphism  as we know what object we are trying to construct at compile time   The only common theme of these two patterns is the hiding of constructors and object creation behind factory methods  and the build method  for improved object construction

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Factory pattern let you create an object at once at once while builder pattern let you break the creation process of an object  In this way  you can add different functionality during the creation of an object

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Both are very much similar   but if you have a large number of parameters for object creation with some of them optional with some default values   go for Builder pattern

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The main difference between them is that the Builder pattern primarily describes the creation of complex objects step by step  In the Abstract Factory pattern  the emphasis is on families of objects-products  Builder returns the product in the last step  While in the Abstract Factory pattern the product is available immediately   Example   Let say that we are creating Maze  1  Abstract Factory   Maze  MazeGame  CreateMaze  MazeFactory amp  factory    Maze  maze   factory MakeMaze        product is available at start       Call some methods on maze    return maze      2  Builder   Maze  MazeGame  CreateMaze  MazeBuilder amp  builder    builder buildMaze        We don t have access to maze     Call some methods on builder    return builder GetMaze

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First some general things to follow my argumentation   The main challenge in designing big software systems is that they have to be flexible and uncomplicated to change  For this reason  there are some metrics like coupling and cohesion  To achieve systems that can be easily altered or extended in its functionality without the need to redesign the whole system from scratch  you can follow the design principles  like SOLID  etc    After a while some developer recognized that if they follow those principles there are some similar solutions that worked well to similar problems  Those standard solutions turned out to be the design patterns   So the design patterns are to support you to follow the general design principles in order to achieve loosely coupled systems with high cohesion   Answering the question   By asking the difference between two patterns you have to ask yourself what pattern makes your system in which way more flexible  Each pattern has its own purpose to organize dependencies between classes in your system   The Abstract Factory Pattern  GoF     Provide an interface for creating families of related or dependent objects without specifying their concrete classes      What does this mean  By providing an interface like this the call to the constructor of each of the family   s product is encapsulated in the factory class  And because this is the only place in your whole system where those constructors are called you can alter your system by implementing a new factory class  If you exchange the representation of the factory through another  you can exchange a whole set of products without touching the majority of your code   The Builder Pattern  GoF     Separate the construction of a complex object from its representation so that the same construction process can create different representations      What does this mean  You encapsulate the process of construction in another class  called the director  GoF   This director contains the algorithm of creating new instances of the product  e g  compose a complex product out of other parts   To create the integral parts of the whole product the director uses a builder  By exchanging the builder in the director you can use the same algorithm to create the product  but change the representations of single parts  and so the representation of the product   To extend or modify your system in the representation of the product  all you need to do is to implement a new builder class   So in short  The Abstract Factory Pattern   s purpose is to exchange a set of products which are made to be used together  The Builder Pattern   s purpose is to encapsulate the abstract algorithm of creating a product to reuse it for different representations of the product   In my opinion you can   t say that the Abstract Factory Pattern is the big brother of the Builder Pattern  YES  they are both creational patterns  but the main intent of the patterns is entirely different

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Build pattern emphasizes on complexity  of creating object  solved by  steps    Abstract pattern emphasizes  just  on  abstraction  of  multiple but related  objects

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One striking difference between Builder  amp  factory which I could make out was the following  suppose we have a car  class Car     bool HasGPS    bool IsCityCar    bool IsSportsCar    int   Cylenders    int Seats     public       void Car bool hasGPs false bool IsCityCar false bool IsSportsCar false  int Cylender 2  int Seats 4         In the above interface we can get car by the following way     int main          BadCar   new Car false false true 4 4         but what if  some exception happens while creating the Seats     YOU WILL NOT GET THE OBJECT AT ALL    BUT  suppose you have implementation like the following   class Car        bool mHasGPS      bool mIsCityCar      bool mIsSportsCar      int mCylenders      int mSeats    public      void Car     mHasGPs false   mIsCityCar false   mIsSportsCar false   mCylender 2   mSeats 4         void SetGPS bool hasGPs false    mHasGPs   hasGPs       void SetCity bool CityCar    mIsCityCar   CityCar       void SetSports bool SportsCar    mIsSportsCar   SportsCar       void SetCylender int Cylender    mCylenders   Cylender           void SetSeats int seat   mSeats   seat            class CarBuilder         Car  mCar  public          CarBuilder   mCar NULL      mCar    new Car                CarBuilder         if mCar         delete mCar               Car  GetCar         return mCar  mCar new Car                 CarBuilder  SetSeats int n      mCar- gt SetSeats n   return this            CarBuilder  SetCylender int n       mCar- gt SetCylender n   return this             CarBuilder  SetSports bool val      mCar- gt SetSports val   return this             CarBuilder  SetCity bool val        mCar- gt SetCity val   return this               CarBuilder  SetGPS bool val         mCar- gt SetGPS val   return this        Now you can create like this    int main         CarBuilder  bp  new CarBuilder      Car  NewCar    bp- gt SetSeats 4 - gt SetSports 4 - gt SetCity ture - gt SetGPS false - gt SetSports true - gt GetCar          bp- gt SetSeats 2         bp- gt SetSports 4         bp- gt SetCity ture         bp- gt SetSports true        Car  Car II   bp- gt GetCar           Here in the second case   even if one operation fails you would still get the Car   May be that car does not works perfectly later but   you would have the object   Because Factory Method gives you the Car in single call   whereas the Builder builds one by one   Although  It depends on the needs of the deign which one to go for

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The main advantage of the builder pattern over factory pattern is in case if you want to create some standard object with lots of possible customizations  but you usually end up customizing just a few    For example  if you want to write an HTTP Client - you ll set up some default parameters like default write read timeout  protocols  cache  DNS  interceptors  etc    Most of the users of your client will just use those default parameters  while some other users might want to customize some of the other parameters  In some cases  you ll just want to change timeouts and use the rest as it is  while in other cases you might need to customize for example the cache    Here are possible ways of instantiating your client  taken from OkHttpClient       just give me the default stuff HttpClient Builder   build         I want to use custom cache HttpClient Builder   cache MyCache    build       I want custom connection timeout HttpClient Builder   connectTimeout 30  TimeUnit SECONDS  build       I am more interested in read write timeout HttpClient Builder            readTimeout 30  TimeUnit SECONDS           writeTimeout 30  TimeUnit SECONDS  build     If you d use a factory pattern for this  you ll end up writing a lot of methods with all possible combinations of creational parameters  With the builder  you just specify those you care about and let the builder build it for you taking care of all those other params

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IMHO  Builder is some kind of more complex Factory   But in Builder you can instantiate objects with using another factories  that are required to build final and valid object   So  talking about  Creational Patterns  evolution by complexity you can think about it in this way   Dependency Injection Container - gt  Service Locator - gt  Builder - gt  Factory

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I believe  the usage of and the difference between Factory  amp  Builder patterns can be understood clarified easier in a certain time period as you worked on the same code base and changing requirements    From my experience  usually  you start with a Factory pattern including couple of static creator methods to primarily hide away relatively complex initialisation logic  As your object hierarchy gets more complex  or as you add more types  parameters   you probably end up having your methods populated with more parameters and not to mention you gonna have to recompile your Factory module  All those stuff  increases the complexity of your creator methods  decreases the readability and makes the creation module more fragile   This point possibly will be the transition extension point  By doing so  you create a wrapper module around the construction parameters and then you will be able represent new  similar  objects by adding some more abstractions perhaps  and implementations without touching actual your creation logic  So you ve had  less  complex logic   Frankly  referring to something sort of  having an object created in one-step or multiple steps is the difference  as the sole diversity factor was not sufficient for me to distinguish them since I could use both ways for almost all cases I faced up to now without experiencing any benefit  So this is what I ve finally thought about it

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Builder and Abstract Factory The Builder design pattern is very similar  at some extent  to the Abstract Factory pattern  That s why it is important to be able to make the difference between the situations when one or the other is used  In the case of the Abstract Factory  the client uses the factory s methods to create its own objects  In the Builder s case  the Builder class is instructed on how to create the object and then it is asked for it  but the way that the class is put together is up to the Builder class  this detail making the difference between the two patterns  Common interface for products In practice the products created by the concrete builders have a structure significantly different  so if there is not a reason to derive different products a common parent class  This also distinguishes the Builder pattern from the Abstract Factory pattern which creates objects derived from a common type   From  http   www oodesign com builder-pattern html

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Many designs start by using Factory Method  less complicated and more customizable via subclasses  and evolve toward Abstract Factory  Prototype  or Builder  more  exible  but more complicated   Builder focuses on constructing complex objects step by step  Implementing it   Clearly define the common construction steps for building all available product representations  Otherwise  you won   t be able to proceed with implementing the pattern  Declare these steps in the base builder interface  Create a concrete builder class for each of the product representations and implement their construction steps   Abstract Factory specializes in creating families of related objects  Abstract Factory returns the product immediately  whereas Builder lets you run some additional construction steps before fetching the product  You can use Abstract Factory along with Bridge  This pairing is useful when some abstractions defined by Bridge can only work with specific implementations  In this case  Abstract Factory can encapsulate these relations and hide the complexity from the client code  Dive into design pattern

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With design patterns  there usually is no  more advantageous  solution that works for all cases  It depends on what you need to implement   From Wikipedia          Builder focuses on constructing a   complex object step by step  Abstract   Factory emphasizes a family of product   objects  either simple or complex     Builder returns the product as a final   step  but as far as the Abstract   Factory is concerned  the product gets   returned immediately    Builder often builds a Composite    Often  designs start out using Factory Method  less complicated  more   customizable  subclasses proliferate    and evolve toward Abstract Factory    Prototype  or Builder  more flexible    more complex  as the designer   discovers where more flexibility is   needed    Sometimes creational patterns are complementary  Builder can use one   of the other patterns to implement   which components get built  Abstract   Factory  Builder  and Prototype can   use Singleton in their   implementations       Wikipedia entry for factory design pattern  http   en wikipedia org wiki Factory method pattern  Wikipedia entry for builder design pattern  http   en wikipedia org wiki Builder pattern

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Constructing a complex object step by step   builder pattern  A simple object is created by using a single method   factory method pattern  Creating Object by using multiple factory method   Abstract factory pattern

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The builder design pattern describes an object that knows how to craft another object of a specific type over several steps   It holds the needed state for the target item at each intermediate step  Think what StringBuilder goes through to produce a final string   The factory design pattern describes an object that knows how to create several different but related kinds of object in one step  where the specific type is chosen based on given parameters  Think of the serialization system  where you create your serializer and it constructs the desired in object all in one load call

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Difference is clear  In builder pattern  builder will create specific type of object for you  You have to tell what builder has to build   In factory pattern   using abstract class you are directly building the specific object   Here builder class acts as mediator between main class and specific type classes   More abstraction

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Both are Creational patterns  to create Object   1  Factory Pattern - Assume  you have one super class and N number of sub classes      The object is created depends on which parameter value is passed   2  Builder pattern - to create complex object   Ex  Make a Loan Object  Loan could be house loan  car loan       education loan   etc  Each loan will have different interest rate  amount         duration    etc  Finally a complex object created through step by step process

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In my opinion  Builder pattern is used when you want to create an object from a bunch of other objects and creation of part needs to be independent of the object you want to create  It helps to hide the creation of part from the client to make builder and client independent  It is used for complex objects creation  objects which may consists of complicated properties   While factory pattern specifies that you want to create objects of a common family and you want it to be cerated at once  It is used for simpler objects

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Builder Pattern and Factory pattern  both seem pretty similar to naked eyes because they both create objects for you  But you need to look closer This real-life example will make the difference between the two more clear  Suppose  you went to a fast food restaurant and you ordered Food  1  What Food  Pizza 2  What toppings  Capsicum  Tomato  BBQ chicken  NO PINEAPPLE So different kinds of foods are made by Factory pattern but the different variants flavors  of a particular food are made by Builder pattern   Different kinds of foods  Pizza  Burger  Pasta  Variants of Pizza  Only Cheese  Cheese Tomato Capsicum  Cheese Tomato etc  Code sample You can see the sample code implementation of both patterns here Builder Pattern Factory Pattern

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A complex construction is when the object to be constructed is composed of different other objects which are represented by abstractions   Consider a menu in McDonald s  A menu contains a drink  a main and a side  Depending on which descendants of the individual abstractions are composed together  the created menu has another representation    Example  Cola  Big Mac  French Fries Example  Sprite  Nuggets  Curly Fries   There  we got two instances of the menu with different representations  The process of construction in turn remains the same  You create a menu with a drink  a main and a side   By using the builder pattern  you separate the algorithm of creating a complex object from the different components used to create it   In terms of the builder pattern  the algorithm is encapsulated in the director whereas the builders are used to create the integral parts  Varying the used builder in the algorithm of the director results in a different representation because other parts are composed to a menu  The way a menu is created remains the same

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Factory  Used for creating an instance of an object where the dependencies of the object are entirely held by the factory  For the abstract factory pattern   there are often many concrete implementations of the same abstract factory  The right implementation of the factory is injected via dependency injection   Builder  Used to build immutable objects  when the dependencies of the object to be instantiated are partly known in advance and partly provided by the client of the builder

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Builder and Abstract Factory have meant for different purposes  Depending on right use case  you have to select suitable design pattern    Builder salient features    Builder pattern builds a complex object using simple objects and using a step by step approach A Builder class builds the final object step by step  This builder is independent of other objects Replacement to Factory method Abstract Factory in this scenario   Too Many arguments to pass from client program to the Factory class that can be error prone Some of the parameters might be optional unlike in Factory which forces to send all parameters   Factory  simple Factory  salient features    Creational pattern Based on inheritance Factory returns a Factory Method  interface  which in turn returns Concrete Object You can substitute new Concrete Objects for interface and client  caller  should not be aware of all concrete implementations Client always access interface only and you can hide object creation details in Factory method    Often  designs start out using Factory Method  less complicated  more customizable  subclasses proliferate  and evolve toward Abstract Factory  Prototype  or Builder  more flexible  more complex    Have a look at related posts   Keeping builder in separate class  fluent interface   Design Patterns  Factory vs Factory method vs Abstract Factory  You can refer to below articles for more details   sourcemaking  journaldev

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A factory is simply a wrapper function around a constructor  possibly one in a different class   The key difference is that a factory method pattern requires the entire object to be built in a single method call  with all the parameters passed in on a single line  The final object will be returned   A builder pattern  on the other hand  is in essence a wrapper object around all the possible parameters you might want to pass into a constructor invocation  This allows you to use setter methods to slowly build up your parameter list  One additional method on a builder class is a build   method  which simply passes the builder object into the desired constructor  and returns the result   In static languages like Java  this becomes more important when you have more than a handful of  potentially optional  parameters  as it avoids the requirement to have telescopic constructors for all the possible combinations of parameters  Also a builder allows you to use setter methods to define read-only or private fields that cannot be directly modified after the constructor has been called   Basic Factory Example     Factory static class FruitFactory       static Fruit create name  color  firmness               Additional logic         return new Fruit name  color  firmness               Usage Fruit fruit   FruitFactory create  apple    red    crunchy      Basic Builder Example     Builder class FruitBuilder       String name  color  firmness      FruitBuilder setName name            this name       name      return this        FruitBuilder setColor color          this color      color     return this        FruitBuilder setFirmness firmness    this firmness   firmness  return this        Fruit build             return new Fruit this      Pass in the builder             Usage Fruit fruit   new FruitBuilder            setName  apple            setColor  red            setFirmness  crunchy            build      It may be worth comparing the code samples from these two wikipedia pages   http   en wikipedia org wiki Factory method pattern http   en wikipedia org wiki Builder pattern

[design-patterns] What is the difference between Builder Design pattern and Factory Design pattern?

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