Difference between Encapsulation and Abstraction

Question

I had an interview today  I had a question from OOP  about the difference between Encapsulation  amp  Abstraction   I replied her to my knowledge that Encapsulation is basically to bind data members  amp  member functions into a single unit called Class  Whereas Abstraction is basically to hide complexity of implementation  amp  provide ease of access to the users  I thought she would be fine with my answer  But she queried  if the purpose of both are to hide information then what is the actual difference between these two  I could not give any answer to her   Before asking this question  I read other threads on StackOverFlow about the difference between these two OOPs concepts  But I am not finding my self in a position to convince the interviewer   Can anyone please justify it with a simplest example

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Abstraction  what are the minimum functions and variables that should be exposed to the outside of our class   Encapsulation  how to achieve this requirement  meaning how to implement it

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Encapsulation is wrapping up of data and methods in a single unit and making the data accessible only through methods getter setter  to ensure safety of data  Abstraction is hiding internal implementation details of how work is done  Take and example of following stack class  Class Stack   private top  void push    int pop       Now encapsulation helps to safeguard internal data as top cannot be accessed directly outside  And abstraction helps to do push or pop on stack without worrying about what are steps to push or pop

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Yes  it is true that Abstraction and Encapsulation are about hiding     Using only relevant details and hiding unnecessary data at Design Level is called Abstraction   Like selecting only relevant properties for a class  Car  to make it more abstract or general   Encapsulation is the hiding of data at Implementation Level  Like how to actually hide data from direct external access  This is done by binding data and methods to a single entity unit to prevent external access  Thus  encapsulation is also known as data hiding at implementation level

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Abstraction  In Java  abstraction means hiding the information to the real world  It establishes the contract between the party to tell about    what should we do to make use of the service       Example  In API development  only abstracted information of the service has been revealed to the world rather the actual implementation  Interface in java can help achieve this concept very well    Interface provides contract between the parties  example  producer and consumer  Producer produces the goods without letting know the consumer how the product is being made  But  through interface  Producer let all consumer know what product can buy  With the help of abstraction  producer can markets the product to their consumers     Encapsulation   Encapsulation is one level down of abstraction  Same product company try shielding information from each other production group  Example  if a company produce wine and chocolate  encapsulation helps shielding information how each product Is being made from each other     If I have individual package one for wine and another one for chocolate  and if all the classes are declared in the package as default access modifier  we are giving package level encapsulation for all classes  Within a package  if we declare each class filed  member field  as private and having a public method to access those fields  this way giving class level encapsulation to those fields

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Let me explain it in with the same example discussed above  Kindly consider the same TV   Encapsulation  The adjustments we can make with the remote is a good example - Volume UP DOWN  Color  amp  Contrast - All we can do is adjust it to the min and max value provided and cannot do anything beyond what is provided in the remote - Imagine the getter and setter here The setter function will check whether the value provided is valid if Yes  it process the operation if not won t allow us to make changes - like we cannot decrease the volume beyond zero even we press the volume down button a hundred times    Abstraction  We can take the same example here but with a higher Degree Context  The volume down button will decrease the volume - and this is the info we provide to the user and the user is not aware of neither the infrared transmitter inside the remote nor the receiver in the TV and the subsequent process of parsing the signal and the microprocessor architecture inside the TV  Simply put it is not needed in the context - Just provide what is necessary  One can easily relate the Text book definition here ie   Hiding the inner implementation and only providing what it will do rather than how it do that   Hope it clarifies a bit

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Encapsulate hides variables or some implementation that may be changed so often in a class to prevent outsiders access it directly  They must access it via getter and setter methods   Abstraction is used to hiding something too but in a higher degree class  interface   Clients use an abstract class or interface  do not care about who or which it was  they just need to know what it can do

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There is a great article that touches on differences between Abstraction  Encapsulation and Information hiding in depth  http   www tonymarston co uk php-mysql abstraction txt  Here is the conclusion from the article      Abstraction  information hiding  and encapsulation are very different    but highly-related  concepts  One could argue that abstraction is a   technique that helps us identify which specific information should be   visible  and which information should be hidden  Encapsulation is then   the technique for packaging the information in such a way as to hide   what should be hidden  and make visible what is intended to be   visible

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A very practical example is  let s just say I want to encrypt my password   I don t want to know the details  I just call encryptionImpl encrypt password  and it returns an encrypted password  public interface Encryption  public String encrypt String password      This is called abstraction  It just shows what should be done   Now let us assume We have Two types of Encryption Md5 and RSA which implement Encryption from a third-party encryption jar  Then those Encryption classes have their own way of implementing encryption which protects their implementation from outsiders This is called Encapsulation  Hides how it should be done    Remember what should be done vs how it should be done  Hiding complications vs Protecting implementations

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difference in both is just the View Point Encapsulation word is used for hiding data if our aim is to prevent client seeing inside view of our logic  Abstraction word is used for hiding data if our aim is to show our client a out side view  Outside view means that let suppose   BubbleSort      code  swap x y       here we use swap in bubble sort for just showing our client what logic we are applying  If we replace swap x y  with whole code here  In a single instance he she can t understand our logic

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Encapsulation   Hiding something  sort of like medicine capsule  We don t know what is in the capsule  we just take it  Same as in programming - we just hide some special code of method or property and it only gives output  same as capsule  In short  encapsulation hides data   Abstraction    Abstraction means hiding logic or implementation  For example  we take tablets and see their color and but don t know what is the purpose of this and how it works with the body

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Just a few more points to make thing clear   One must not confuse data abstraction and the abstract class  They are different   Generally we say abstract class or method is to basically hide something  But no    That is wrong  What is the word abstract means   Google search says the English word abstraction means    Existing in thought or as an idea but not having a physical or concrete existence    And thats right in case of abstract class too  It is not hiding the content of the method but the method s content is already empty  not having a physical or concrete existence  but it determines how a method should be  existing in thought or as an idea  or  a method should be in the calss   So when do you actually use abstract methods      When a method from base class will differ in each child class that extends it  And so you want to make sure the child class have this function implemented  This also ensures that method  to have compulsory signature like  it must have n number of parameters    So about abstract class  - An Abstract class cannot be instantiated only extended  But why     A class with abstract method must be prevented from creating its own instance because the abstract methods in it  are not having any meaningful implementation  You can even make a class abstract  if for some reason you find that it is meaning less to have a instance of your that class    An Abstract class help us avoid creating new instance of it   An abstract method in a class forces the child class to implement that function for sure with the provided signature

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Encapsulation  Wrapping code and data together into a single unit  Class is an example of encapsulation  because it wraps the method and property     Abstraction  Hiding internal details and showing functionality only  Abstraction focus on what the object does instead of how it does  It provides generalized view of classes   int number   5  string aStringNumber   number ToString       Here  ToString   is abstraction  And how this mechanism number variable converted to string and initialize into aStringNumber is encapsulation   Let us take a real world example of calculator  Encapsulation is the internal circuits  battery  etc   that combine to make it a calculator  Abstraction is the different buttons like on-off  clear and other buttons provided to operate it

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Briefly  Abstraction happens at class level by hiding implementation and implementing an interface to be able to interact with the instance of the class  Whereas  Encapsulation is used to hide information  for instance  making the member variables private to ban the direct access and providing getters and setters for them for indicrect access

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Abstraction  Is usually done to provide polymorphic access to a set of classes  An abstract class cannot be instantiated thus another class will have to derive from it to create a more concrete representation   A common usage example of an abstract class can be an implementation of a template method design pattern where an abstract injection point is introduces so that the concrete class can implement it in its own  concrete  way   see  http   en wikipedia org wiki Abstraction  computer science   Encapsulation  It is the process of hiding the implementation complexity of a specific class from the client that is going to use it  keep in mind that the  client  may be a program or event the person who wrote the class   see  http   en wikipedia org wiki Encapsulation  object-oriented programming

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If I am the one who faced the interview  I would say that as the end-user perspective abstraction and encapsulation are fairly same  It is nothing but information hiding  As a Software Developer perspective  Abstraction solves the problems at the design level and Encapsulation solves the problem in implementation level

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Abstraction - is the process  and result of this process  of identifying the common essential characteristics for a set of objects  One might say that Abstraction is the process of generalization  all objects under consideration are included in a superset of objects  all of which possess given properties  but are different in other respects    Encapsulation - is the process of enclosing data and functions manipulating this data into a single unit  so that to hide the internal implementation from the outside world    This is a general answer not related to a specific programming language  as was the question   So the answer is  abstraction and encapsulation have nothing in common  But their implementations might relate to each other  say  in Java  Encapsulation - details are hidden in a class  Abstraction - details are not present at all in a class or interface

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Yes      If I say Encapsulation is a kind of an advanced specific scope abstraction  How many of you read upvote my answer  Let s dig in why I am saying like this  I need to clear two things before my claiming  One is data hiding and   another one is the abstraction  Data hiding  Most of the time  we will not give direct access to our internal data  Our internal data should not go out directly that is an outside person can t access our internal data directly  It s all about security since we need to protect the internal states of a particular object    Abstraction  For simplicity  hide the internal implementations is called abstraction  In abstraction  we only focus on the necessary things  Basically  We talk about  What to do  and not  How to do  in abstraction  Security also can be achieved by abstraction since we are not going to highlight  how we are implementing   Maintainability will be increased since we can alter the implementation but it will not affect our end user   I said   quot Encapsulation is a kind of an advanced specific scope abstraction quot    Why  because we can see encapsulation as data hiding   abstraction  encapsulation     data hiding     abstraction  In encapsulation  we need to hide the data so outside person can not see the data and we need to provide methods that can be used to access the data  These methods may have validations or other features inside those things also hidden to an outside person  So here  we are hiding the implementation of access methods and it is called abstraction  This is why I said like above encapsulation is a kind of abstraction  So Where is the difference  The difference is the abstraction is a general one if we are hiding something from the user for simplicity  maintainability and security and  encapsulation is a specific one for which is related to internal states security where we are hiding the internal state  data hiding  and we are providing methods to access the data and those methods implementation also hidden from the outside person abstraction

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This image sums pretty well the difference between both   Source here

[oop] Difference between Encapsulation and Abstraction

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