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Essentially, encapsulation prevents external code from being concerned with the internal workings of an object. Encapsulation allows developers to present a consistent interface that is independent of its internal implementation. As one example, encapsulation can be used to hide the values or state of a structured data object inside a class.
The class will be accessible to other classes in the same package but will be inaccessible to classes outside the package. When we say that a class is inaccessible, it simply means that we cannot create an object of that class or declare a variable of that class type. The protected access specifier too cannot be applied to a class.
The bridge pattern is a design pattern used in software engineering that is meant to "decouple an abstraction from its implementation so that the two can vary independently", introduced by the Gang of Four. [1]
In this example of a simple class representing a student with only the name stored, one can see the variable name is private, i.e. only visible from the Student class, and the "setter" and "getter" are public, namely the "getName()" and "setName(name)" methods.
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 ...
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. As such, encapsulation is a core principle of good software architecture, at every level of granularity.
Encapsulation may be weakened in several ways, including: By declaring internal members public, or by providing free access to data via public mutator methods (setter). By providing non-public access. For example, see: Java access modifiers and accessibility levels in C# [1] In C++, via some of the above means, and by declaring friend classes ...
Composition over inheritance (or composite reuse principle) in object-oriented programming (OOP) is the principle that classes should favor polymorphic behavior and code reuse by their composition (by containing instances of other classes that implement the desired functionality) over inheritance from a base or parent class. [2]