In object-oriented programming (OOP), encapsulation refers to the bundling of data with the methods that operate on that data, or the restricting of direct access to some of an object's components.Encapsulation is used to hide the values or state of a structured data object inside a class, preventing unauthorized parties' direct access to them. Publicly accessible methods are generally provided in the class (so-called "getters" and "setters") to access the values, and other client classes call these methods to retrieve and modify the values within the object.
This mechanism is not unique to OOP. Implementations of abstract data types, e.g., modules, offer a similar form of encapsulation. The similarity has been explained by programming language theorists in terms of existential types.
Some programming language researchers and academics use the first meaning alone or in combination with the second as a distinguishing feature of object-oriented programming, while some programming languages that provide lexical closures view encapsulation as a feature of the language orthogonal to object orientation.
The second definition is motivated by the fact that in many object-oriented languages, and other related fields, the components are not hidden automatically and this can be overridden; thus, information hiding is defined as a separate notion by those who prefer the second definition.
The features of encapsulation are supported using classes in most object-oriented languages, although other alternatives also exist.
