Software Engineering: Object-Oriented Programming Concepts Explained

Object-Oriented Programming Concepts Explained
Object-Oriented Programming Concepts Explained

As computer systems and technologies continue to advance, so do computer science skills. Computer science experts are familiar with today's most popular programming languages and continue to build competencies that make them more efficient, strategic, and effective developers. Object-oriented programming (OOP) is the foundation of many widely used programming languages, including Java, C++, and Python. Today, data analysts, software engineers, software developers, and other professionals in the field of computer science use the main concepts of OOP to construct objects used throughout the programming cycle. For example, OOP is essential to preserve and reuse code in the Java programming language while upholding security. Discover the critical object-oriented programming concepts and real-world object-oriented programming examples that software engineers must understand to complete their day-to-day responsibilities.

What are the Main Concepts of Object-oriented Programming?

Object-oriented programming (OOP) is a programming model that operates at the root of today's commonly used programming languages. Three fundamental concepts comprise OOP, including classes and instances, inheritance, and encapsulation. As the name implies, software engineers use OOP to fragment programs into the objects contained within them. Software engineers can also use OOP to make changes and operate on software functions and data.

Classes and Instances

The classes and instances in OOP refer to the abstract definitions that symbolize objects within a computer software program. In OOP, a class is a template used to create things within that umbrella category. An instance refers to the objects that are categorized within each class. For example, if the class for an e-commerce website is "women's clothing," this would be the "parent" class that would include types of women's clothing like dresses, tops, trousers, accessories, etc. Each type would be considered the "child" class within the parent category and have associated attributes that differentiate them. The differentiators are data points that allow for granular segmentation. Next, programmers use constructors to define each instance. In this example, colours, sizes, prices, and other variables would help define and construct each instance.

A programmer may use the classes, instances, and constructors to create keywords on a website for an item such as a "new red, size four women's dress priced at $200." Each keyword and variable would be visible in the coding language on a website to build a storefront and allow businesses to upload, advertise, and sell clothing online. Of course, this OOP paradigm is not just used for online shopping; it can be employed to list and categorize everything from financial stocks and automobiles to people employed at an organization or students enrolled at a university.


Inheritance allows programmers to classify properties that share certain attributes. Developers can model a new class and define commonalities. In the example above, purses and jewelry both fall into the accessory category and share the same parent class. The e-commerce site might also filter by categories such as "popular items," "back in stock," or "new items." Say a dress, top, and pair of shoes fall into the "new items" section of the storefront. In this case, all items, regardless of their parent category, would be tagged and fall temporarily into this section; this is known as polymorphism. Finally, there are certain cases where a subclass can override its superclass and share the same implementation as other items. Inheritance allows programmers to modify objects while sustaining commonalities.


One of the benefits of OOP is that it allows programmers to alter data without disrupting the entire code or existing properties. An object's state is private, meaning other objects can not influence or change the state of one object. The barrier between the general, publicly-available interface and the back-end interface is called encapsulation. Encapsulation is helpful for upholding data privacy and security. This is especially relevant within programs that already understand certain attributes of their users and can serve personalized content to users with specific qualifications. For example, say a website requires users to log in to access additional benefits, and VIP members can buy specialized products. The system can detect "VIP" as the internal state of an object or user and limit other objects without this tag from accessing the same content. Objects that attempt to access content outside of their allowance will be directed to an error page.

Example of Object-oriented Programming Concepts in Java

Example of Object-oriented Programming Concepts in Java

Objects and inclusions, inheritance, and encapsulation make up the main concepts of OOP, but other concepts work in tandem to deliver the optimal programming capacity. When a programmer enlists OOP in the programming language Java, they will learn all of the concepts below:

  • Class: The classification of objects in OOP.
    • Modifiers: Public or default access.
    • Class name: Initial letter.
    • Superclass: Parent class.
    • Interfaces: A class can implement more than one interface.
    • Body: Surrounded by braces { } in coding.
  • Object: The instances of a class that contains specific attributes or behaviours.
    • Mybook Myobj= new Mybook (); a system used for object creation.
    • System.out.println(Myobj.x); a technique used to replace the value of x of an object.
  • Inheritance: A hierarchical classification method of objects into the appropriate super- and subclasses.
    • Single
    • Multilevel
    • Multiple
    • Hybrid
    • Hierarchical
  • Polymorphism: A process in OOP that serves a single action in multiple ways.
    • Static / Compile-Time Polymorphism
    • Dynamic / Runtime Polymorphism
  • Abstraction: Collecting all necessary information and hiding unnecessary or private information.
  • Encapsulation: Secure data storage that protects information from outside interference via data hiding
  • Coupling: In Java, this denotes the relationship between two classes in an OOP.
    • Tight coupling
    • Loose coupling
  • Cohesion: In Java, this measures how classified methods and attributes are strongly related to each other to identify data patterns and determine the system's overall performance.
    • Low cohesion
    • High cohesion
  • Association: In Java, this is the relationship between two disparate classes with the help of their child objects.
  • Aggregation: In Java, this is a weak association between objects containing other objects.
  • Composition: In Java, this is the association representing a component of an entire relationship where a part cannot exist without a whole. For example, a room object cannot exist without a school object.

The Benefits and Disadvantages of Object-oriented Programming

OOP offers many advantages; however, building software that is easy to use can be more complex to build. Additionally, OOP is only usable within some programming languages and is more useful for specific applications. The following represents the typical benefits and drawbacks of using OOP.

The Benefits of OOP:

  • Increased productivity: Instead of writing code by scratch, programmers can use OOP to develop standardized working models that interact with one another quickly.
  • Manageable: Programmers can segment each program into components and edit objects one at a time.
  • Reduced cost: The OOP method allows programmers to save time and improve efficiency, which ultimately reduces overhead costs.
  • Innovative: Programmers can make necessary upgrades to systems of all sizes, which accelerates opportunities for innovation.
  • Better project management: Isolated objects allow programmers to delegate work on a project-by-project basis.
  • Enhanced tracking: Project managers can use OOP to more easily associate a problem with an object and track coding errors.
  • Strong security and privacy: OOP allows programmers to hide select data to maintain security systems and avoid potential threats or breaches.
  • Efficient: The inheritance feature allows programmers to reuse existing classes and duplicate code while editing or adding new variables.
  • Seamless communication: OOP allows information to pass between objects to simplify descriptions and external displays.
  • Data-driven: The entire methodology allows systems to capture more data and categorize these details for use.

The Drawbacks of OOP:

  • Size of the program: Although already-built OOP programming is efficient, it takes longer to build the initial program. Additionally, the OOP language contains many classifications and data points that make OOP large in size.
  • Speed: OOP may slow down programs due to the program's size.
  • Specialized: OOP is not a universal language and can only be used with certain programming languages and applications.
  • Skill-restricted: Only highly skilled programmers with an organized plan can reap the benefits of OOP.
  • Requires planning: OOP is an organized programming method and also demands a strategy for success.
  • Object-dependent: As the name infers, OOP can only classify specific objects and is restricted to object-dependent use cases.

Explore Object-oriented Programming Examples

The best way to understand object-oriented programming is through real-world applications. There are nine applications where programmers would commonly enlist OOP, including:

  1. Client-server systems: OOP is used to build IT infrastructure. This model splits tasks and workloads between servers and deals with operating systems, networks, and hardware.
  2. Object-oriented database management systems (ODBMS): These databases contain objects (defined by OOP) with attributes to determine characteristics and behaviours.
  3. Real-time system design: This form of system and software design allows programmers to adopt agile procedures that help businesses complete real-time data processing.
  4. Simulation and modelling system: OOP is integral to simulation and modelling systems that deal with probability, including applications like weather forecasting, car crash modelling, and predictive testing models.
  5. Hypertext and hypermedia: These components are used to design and enhance user experience (UX) on web platforms. For example, websites like YouTube offer an enhanced multimedia experience with video, text, and clickable content.
  6. Neural networking and parallel programming: This type of programming mirrors the systems of the human brain to deliver faster computational capabilities.
  7. Office automation systems: This automated documentation allows programmers to collect, store, transfer, alter and use office information to streamline tasks. OOP is used to classify objects within this suite of programs.
  8. CIM/CAD/CAM systems: This stands for Computer Integrated Manufacturing (CIM), Computer-Aided Design (CAD), and Computer-Aided Manufacturing (CAM). These systems use OOP to automate repetitive manual tasks and lead to an error-free manufacturing process.
  9. AI expert systems: Artificial intelligence (AI) enlists OOP in AI expert systems to allow computing algorithms to mirror human-like decision-making and solve complex programs through data-driven code.

Learn Advanced Programming Skills in an Online Master of Computer Science Degree

Are you interested in learning foundational and advanced programming skills to enter a rewarding career in computer science? Wilfrid Laurier University is the only university in Canada that offers a 100% online Master of Computer Science Degree.

The program allows students to cultivate in-demand computer science skills, including parallel programming, application development, algorithm design, data mining and analysis, cyber-attack and defence, and machine learning. The program also teaches students business acumen that prepares graduates to work for innovative, data-driven organizations and pursue a career in technology entrepreneurship. The curriculum includes specialized courses that bridge the gap from the classroom to today's top computer science jobs, including courses like iPhone and Android Application Programming. For those looking to start out with OOP from a beginner level, CP213 (OOP) is part of Laurier’s pathway program that upon completion will grant direct access to the Master of Computer Science program.

Build requisite skills and hands-on experience with the latest programming languages and technologies by earning your Master of Computer Science online from Laurier, a world-class Canadian university.

Learn more about Wilfrid Laurier University's Online Master of Computer Science.