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The features of encapsulation are supported using classes in most object-oriented languages, although other alternatives also exist. Encapsulation may also refer to containing a repetitive or complex process in a single unit to be invoked. Object-oriented programming facilitate this at both the method and class levels.
Data encapsulation, also known as data hiding, is the mechanism whereby the implementation details of a class are kept hidden from the user. The user can only perform a restricted set of operations on the hidden members of the class by executing special functions commonly called methods to prevent attributes of objects from being easily viewed and accessed.
In object oriented programming, objects provide a layer which can be used to separate internal from external code and implement abstraction and encapsulation. External code can only use an object by calling a specific instance method with a certain set of input parameters, reading an instance variable, or writing to an instance variable.
In this sense, the idea of encapsulation is more general than how it is applied in object-oriented programming. For example, a relational database is encapsulated in the sense that its only public interface is a query language (such as SQL ), which hides all the internal machinery and data structures of the database management system.
Encapsulation is a means of information hiding. [2] Layered designs in information systems are another embodiment of separation of concerns (e.g., presentation layer, business logic layer, data access layer, persistence layer). [3] Separation of concerns results in more degrees of freedom for some aspect of the program's design, deployment, or ...
The meaning of these modifiers may differ from one language to another. A comparison of the keywords, ordered from the most restrictive to the most open, and their meaning in these three languages follows. Their visibility ranges from the same class to the package where the class is defined to a general access permission.
A language that provides an encapsulation construct for state, behavior, and identity is classified as object-based. If the language also provides polymorphism and inheritance it is classified as object-oriented. A language that supports creating an object from a class is classified as class-based.
Class-based programming, or more commonly class-orientation, is a style of object-oriented programming (OOP) in which inheritance occurs via defining classes of objects, instead of inheritance occurring via the objects alone (compare prototype-based programming).