When
creating a software system for a particular problem domain, the problem is
carefully analyzed and a design or working model is worked upon [1]. If this
process involves an object-oriented point of view, then it is called
object-oriented analysis and design (OOAD) process [1]. The design or model is
created in the OOAD process using class diagrams [4]. To implement such model,
object-oriented programming (OOP) is needed [1]. OOP is currently the world’s
most widely practiced programming paradigm [1].
History
Alan
Kay is considered to be the inventor of what we call today “object-oriented
development” [8]. Before the notion of having real world objects to solve
problems, structured programming was in place [2]. The major drawback of this
approach was that data was not secure [2]. Additionally, there was problem with
manageability of software system for large systems [2]. OOP was introduced to
tackle these problems [2]. The OOP introduced ways to limit access to data and
many design patterns and architectures were introduced around OOP to manage
complex systems. There were many different works by many different inventors
around the world for OOP starting from the 1960s [8]. Among them, the main two
notable contributions were created by Bjarne Stroustrup in 1979 with the invention
of C++ and by James Gosling in 1995 with the invention of Java [3, 6]. The
essence of OOP has remained the same throughout these years however various OOP
languages, frameworks and design patterns have come out and become popular [9].
The frameworks provide boilerplate code for rapid application development and
the design patterns plus architecture provide best practice guidelines for maintainable
code [9, 10]. Some popular frameworks are Spring (Java), Express (JavaScript),
Laravel (PHP), etc. SOLID and GRASP are examples of prevalent OOP architectures
and Singleton, Factory, etc. are popular design patterns nowadays [9, 10].
Major
Concepts
OOP
involves the following major three concepts: Encapsulation, Inheritance and
Polymorphism [2]. Encapsulation is the representation of a real-world entity by
combining the characteristics and the associated behaviors of that entity [2].
It is implemented by the use of a class that encapsulates data and methods that
act on the data [2]. It provides data hiding by utilizing access modifiers
thereby providing data security on need basis [2]. Inheritance provides
hierarchical categorization of real-world entities, so as to conveniently model
the system [2]. It is implemented by the use of superclass-subclass
relationship where common characteristics and behaviors are implemented in
superclass and specialized characteristics and behaviors are implemented in
subclass [2]. It provides code reusability where once written and tested class
can be reused later in the inheritance hierarchy [2]. Polymorphism means having
multiple behavioral forms depending on the entity or context [2]. It is
implemented by the use of method overloading which provides context at compile
time and method overriding which provides context at runtime [2]. It increases
code readability, reduces code redundancy and supports lose coupling thereby
making code more maintainable for developers [2].
The
OOP languages are basically divided into following three types according to their
inclination towards object-orientation [8]:
- Pure OO languages: In these languages, everything is object including primitives [8]. Most popular example is Ruby [8].
- OO with procedural components: In these languages, there are procedural components like primitives but they support all features of pure OO languages [8]. Most popular example is Java [8].
- Object based languages / Prototype-based languages: In these languages, they do not include all the features of object orientation or have support in a different way [7]. Most popular example is JavaScript which is used to provide prototype-based full object orientation but currently can provide object-based also [8].
Implementation
The
most pervasive programming language in the world currently is Java [6]. Java
supports all features of OOP plus contains some procedural features like
primitives and lambdas [6]. It provides encapsulation by the use of a class utilizing
access modifiers like private, package-private (default), protected and public as:
Similarly,
Java provides inheritance with superclass-subclass relationship as:
Further,
Java provides polymorphism in many ways out of which one example is:
In
this implementation of polymorphism, the appropriate version of myMethod() is
called depending on the object that is in context. This is called dynamic
polymorphism or late binding in Java [6]. We also have static polymorphism or
early binding in Java via method overloading [6].
JavaScript
(JS) is another popular language in the world. But it is used for more of
functional programming rather than object-oriented [7]. In current version of
JS, functions are objects [5,7]. Earlier JS used to be object based only but
with the introduction of class in ECMAScript 6, it can now support object
orientation [5]. Also, with the introduction of asynchronous programming in JS,
it is currently one of the most powerful programming languages [5].
For
OO, we can write encapsulation code in JS as:
The same code with class can be written nowadays as:
Inheritance in JS can be achieved similar to Java as:
Polymorphism
in JS can be realized as:
Thus,
we can conclude that JavaScript and Java are both powerful languages as both
can be used to implement OOP and solve real-world problems. However, Java is
more preferred in electronic devices and large financial applications such as
banks whereas JavaScript is more chosen for web development for both client-side
and server-side programming [6, 7].
Further
Reading
Due
to the limitation of time and other constraints, this work cannot get into more
detail explaining every aspect of OOP. As an enthusiast on the art of OOP, it
might be a good idea to take a deep dive on Gang of Four, SOLID, and GRASP techniques
[10]. Further newer technologies like asynchronous programming may be a good
topic for another study.
References
- Deitel, P., & Deitel, Harvey M. (2012). Java : How to program (9th ed., How to program series). Upper Saddle River, N.J.: Prentice Hall.
- Ganesh, S.G., Kiran H., & Sharma T. (2016). Oracle Certified Professional Java SE 8 Programmer Exam 1Z0-809: A Comprehensive OCPJP 8 Certification Guide. Apress.
- https://en.wikipedia.org/wiki/C++
- https://en.wikipedia.org/wiki/Class_diagram
- https://en.wikipedia.org/wiki/ECMAScript
- https://en.wikipedia.org/wiki/Java_(programming_language)
- https://en.wikipedia.org/wiki/JavaScript
- https://en.wikipedia.org/wiki/Object-oriented_programming
- https://en.wikipedia.org/wiki/Software_design_pattern
- https://en.wikipedia.org/wiki/SOLID
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