In software development, an object is an entity semantic that has state, behavior, and identity.[1] [2] [3] [4] An object can model some part of reality or can be an invention of the design process whose collaborations with other such objects serve as the mechanisms that provide some higher-level behavior. Put another way, an object represents an individual, identifiable item, unit, or entity, either real or abstract, with a well-defined role in the problem domain.
A programming language can be classified based on its support for objects. 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.[5] A language that supports creating an object from a class is classified as class-based. A language that supports object creation via a template object is classified as prototype-based.
The concept of object is used in many different software contexts, including:
In purely object-oriented programming languages, such as Java and C#, all classes might be part of an inheritance tree such that the root class is Object, meaning all objects instances of Object or implicitly extend Object.