Encapsulation vs Abstraction?
Here are the brief definitions of encapsulation and abstraction.
Abstraction:
The process of abstraction in Java is used to hide certain details and only show the essential features of the object. In other words, it deals with the outside view of an object (interface). The only good example i see for this across different sites is interface.
Encapsulation:
Its basically about hiding the state of object with the help of modifiers like private,public,protected etc. we expose the state thru public methods only if require.
What we achieve with modifiers like private , public also hides unnecessary details from out side world which is nothing but also a abstraction concept
So, from above explanation looks like encapsulation is a part of abstraction or we can say it's a subset of abstraction. But why then encapsulation term is invented when we could deal it with abstraction only? I am sure there should be some major difference which distinguishes them but most of material on net says almost same thing for both of them.
Though this question has been raised on this forum earlier too but I am posting it again with specific doubts. Some replies also says abstraction is a concept and encapsulation is implementation. But I don't buy this - If it is true, then I can think these two different concepts are provided to confuse us.
Update:- After 5 years i have come up with my own answer whichs is the gist based on answers in this post and below ones
Encapsulation is a strategy used as part of abstraction. Encapsulation refers to the state of objects - objects encapsulate their state and hide it from the outside; outside users of the class interact with it through its methods, but cannot access the classes state directly. So the class abstracts away the implementation details related to its state.
Abstraction is a more generic term, it can also be achieved by (amongst others) subclassing. For example, the interface List in the standard library is an abstraction for a sequence of items, indexed by their position, concrete examples of a List are an ArrayList or a LinkedList . Code that interacts with a List abstracts over the detail of which kind of a list it is using.
Abstraction is often not possible without hiding underlying state by encapsulation - if a class exposes its internal state, it can't change its inner workings, and thus cannot be abstracted.
Abstraction is the concept of describing something in simpler terms, ie abstracting away the details, in order to focus on what is important (This is also seen in abstract art, for example, where the artist focuses on the building blocks of images, such as colour or shapes). The same idea translates to OOP by using an inheritance hierarchy, where more abstract concepts are at the top and more concrete ideas, at the bottom, build upon their abstractions. At its most abstract level there is no implementation details at all and perhaps very few commonalities, which are added as the abstraction decreases.
As an example, at the top might be an interface with a single method, then the next level, provides several abstract classes, which may or may not fill in some of the details about the top level, but branches by adding their own abstract methods, then for each of these abstract classes are concrete classes providing implementations of all the remaining methods.
Encapsulation is a technique. It may or may not be for aiding in abstraction, but it is certainly about information hiding and/or organisation. It demands data and functions be grouped in some way - of course good OOP practice demands that they should be grouped by abstraction. However, there are other uses which just aid in maintainability etc.
encapsulation is a part of abstraction or we can say its a subset of abstraction
They are different concepts.
Abstraction is the process of refining away all the unneeded/unimportant attributes of an object and keep only the characteristics best suitable for your domain.
Eg for a person: you decide to keep first and last name and SSN. Age, height, weight etc are ignored as irrelevant.
Abstraction is where your design starts.
Ie data and methods are bundled together.
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