What is object-oriented programming, or OOP, in Java? Whether you’re studying programming as a hobby or a career choice, you will find that using Java is inevitable. This universal programming language is one of the easiest to learn and use, hence its undeniable popularity. However, to fully understand and reap the benefits of Java as a programming alphabet, you need to understand the various methods you can use it to write code. One of Java’s writing methods is object-oriented programming.

This article will explain the principles of object-oriented programming in Java. This code-writing language has several integral principles, such as encapsulation, abstraction, inheritance and polymorphism.

What is Java?

As previously stated, Java is a universal coding and programming language. Think of Java as the foundation that helps you build websites, programs, and applications; you name it using the Java Virtual Machine (JVM) which you simply install on your device. That’s not everything Java does; it gets rid of any data you don’t need anymore by itself using its Garbage Collection feature. Java also automatically handles any errors in your program without stopping or breaking down the program.

One of Java’s elements is object-oriented programming, which is the building block of your software. Object-oriented programming is a method of observing code that models real-world entities and their interactions. To bring your code to life, you need the JVM, which translates elements into machine code and executes the program.

What is Object-Oriented Programming?

Object-oriented programming, often known as OOP, is a way to plan your code. It’s like building with blocks! There are several main elements in object-oriented programming; the “objects” are the building blocks which encapsulate “properties” and the code that operates on that data “methods”. Object-oriented programming is important because it creates more maintainable, reusable and scalable code.

Object oriented programming in java

Think of these “objects” as two main parts: data and code. Each of them has a part to play, and they must work together for the program to run smoothly. Data can be anything to describe the object, such as a banner’s colour is blue, whereas code informs us what the object does, and the banner explains the festival details.

Key Object-Oriented Programming Concepts in Java

Object-oriented programming in Java concepts are Classes, Objects, Encapsulation, Inheritance, Abstraction, Polymorphism and Interfaces.
Object-oriented programming in Java concepts are Classes, Objects, Encapsulation, Inheritance, Abstraction, Polymorphism and Interfaces.

We’ve learned that object-oriented programming includes objects and properties. Other elements join these two in object-oriented programming in Java. Put together, we will have Classes, Objects, Encapsulation, Inheritance, Abstraction, Polymorphism and Interfaces. Each concept plays a crucial role in designing and implementing efficient and modular code. 

  1. Classes

A class in Java is like a blueprint. It guides us on how to make an object. Think of it as a ground map of a construction project; the soil and surrounding elements will determine the building’s shape and height. In Java, we use classes to describe how the building will eventually look like.

To add details to the building, we use Attributes. With these attributes or templates, we can make many objects with the same details but have their own unique values. Then, we use Methods, which are a part of Classes, to tell the objects what they can do through commands. So, whenever you see a Class in Java, you know it’s there to help you create and control Objects.

  1. Objects

An Object is one of the essential aspects of object-oriented programming in Java. It is a sequence of Classes that represent a real-world entity or a logical concept with distinct states and behaviour. The object’s state is its current condition or attributes, otherwise known as variables. An object’s behaviour is defined by the methods or functions it can perform.

Think of objects as little workers that carry out specific tasks for you on your command! They play a big part in making Java strong with its focus on hiding details not needed for the job at hand; we call this concept abstraction. Methods operate on the object’s state, manipulating its data or interacting with other objects. Packaging data and methods into one class to control who can access them is encapsulation in action. This ensures our data stays safe and sound and takes us to the next concept.

  1. Encapsulation and Information Hiding

In object-oriented programming, we use a method called encapsulation. This method does what it says: it encapsulates data and methods into a single unit, an object. The encapsulation concept helps keep data safe by hiding details about the object and controlling access to data through public interfaces or methods. So, we put data and methods into objects, like boxes.

Encapsulation has an incredible advantage in that it allows us to reuse the code endlessly, making programming easier for programmers. This concept helps make clean code, shielded from unauthorised access, that programmers can manage better over time, protects data integrity and promotes modularity.

  1. Inheritance

As a key concept in object-oriented programming, inheritance enables us to create new classes that inherit attributes and methods from existing classes. We call the existing classes Superclasses and the new ones Subclasses. The subclass gets all the properties of the superclass and can also add its own unique properties or override existing ones. This concept allows us to reuse code and establish hierarchal relationships between classes.

It’s worth noting that to implement inheritance in Java, we use the keyword “extends”. Additionally, a class can only inherit from one superclass, also termed Single Inheritance in Java.

  1. Abstraction

Abstraction plays a vital role in object-oriented programming (OOP) in Java. It helps to simplify complex systems by hiding unnecessary details and showing only the essential attributes. Abstraction creates models or representations of real-world entities, allowing us to focus on what’s important and ignore the rest. Developers can use abstraction to create modular and reusable components that make their code easier to manage and understand.

We use classes and interfaces to achieve abstraction. A class resembles a blueprint for creating objects, while an interface defines a set of methods that a class must implement. With these tools, developers can create abstract classes and interfaces that provide a clear structure for their code without getting into complicated details. This process allows developers to write cleaner code that is easier to read and maintain. It also promotes modularity and reusability by allowing different parts of a program to work independently.

  1. Polymorphism

As a key concept in object-oriented programming, Polymorphism allows different classes to use the same interface, and it represents the ability of objects from numerous classes to respond differently to the same method call. If you remember, we talked about inheritance, where subclasses inherit the characteristics of superclasses. Polymorphism means that all Java objects are polymorphic because, in some way, they all share common characteristics.

Polymorphism can be used to define multiple behaviours for the same method or class, making it a powerful tool for generating flexible and reusable code in Java programming. It also enhances flexibility and code reusability.

  1. Interfaces

In object-oriented programming, Interfaces are the blueprint that clarifies what contracts the classes must adhere to by specifying the set of methods the class must implement. This promises that the class makes when implementing an interface is to provide the exact methods defined in the interface. Such a step helps ensure consistency and allows for easier code maintenance.

Additionally, interfaces are a key part of abstraction and polymorphism in Java. By defining an interface, you can specify what methods a class implementing that interface must have. This clarifies the importance of interfaces in OOP design and plays a crucial role in generating well-structured, modular, and flexible Java applications.

Java Constructors and Methods

Java Constructors are special methods in Java that are used to initialise objects of a class. The constructors have the same name as the class and do not have a return type. Conversely, methods are blocks of code that perform specific actions and can accept parameters and return values.

What are Constructors in Java?

In essence, constructors are vital to object-oriented programming in Java. They are the main methods developers use to initialise objects. When you create an object in a certain class, the constructor automatically sets the initial value of the object’s attributes or variables.

When we say that constructors can have parameters, it means they can accept values during object initialisation. This process allows for more flexibility in creating objects with different initial attribute values. In Java, a term called Constructor Overloading refers to multiple constructors with different parameter lists.

How Methods Work in Java

As an essential part of Java programming, methods are of two types: user-defined methods and built-in methods. The former type is created based on specific needs, while the latter is built into Java itself, hence the name. We can say that constructors and methods are similar but with different names and purposes.

These two components, methods and constructors, exist in a Java class alongside a third component, fields. Like constructors, methods can have parameters, referred to as inputs, and return values, referred to as outputs. Moreover, you can have multiple methods with the same name but with different parameters or return types, and we call this process Overloading.

Advantages and Disadvantages of Object-Oriented Programming in Java

Advantages and Disadvantages of Object-oriented Programming in Java
Advantages and Disadvantages of Object-oriented Programming in Java

Although object-oriented programming in Java has numerous advantages, such as reusability and modularity, it has several drawbacks, such as increased complexity and slower execution speed.

Advantages of OOP in Java

We’ve mentioned several object-oriented programming advantages that include modularity, reusability and easier maintenance, just to name a few.

  1. Modularity and Code Organisation

Modularity is one of OOP’s known advantages. This term means we can divide code into smaller, more manageable parts, which we know are called Classes. Each class has its own variables and methods, which makes organising and troubleshooting code easier. Additionally, breaking down code into smaller pieces helps us to focus on errors in certain classes instead of searching through the entire code to identify the error.

  1. Code Reusability

Code reusability is tied with inheritance and polymorphism in object-oriented programming. Initially, code reusability means we can use classes in numerous parts of an application or even in different projects, which saves time and effort and reduces redundancy. When we use inheritance to create new classes based on existing ones, we are reusing code from a superclass to make changes or additions in a subclass as needed.

For polymorphism, it allows us to treat objects from different classes as if they were objects belonging to the same superclass. Hence, extending our code without modifying existing implementations promotes flexibility and easiness.

  1. Maintainability

Object-oriented programming in Java promotes maintainability through encapsulation. This process protects internal data from direct modification and reduces the risk of reduces the risk of unintentional side effectsside effects. It also allows us to make changes to one class without affecting other parts of the code, which makes it easier to maintain and update applications.

  1. Extensibility

How object-oriented programming in Java promotes extensibility is through its inheritance concept. Since this concept enables us to create new classes, it “extends” the functionality of existing classes to new ones. This allows easy addition of new features without needing to modify existing code and makes applications more adaptable to changing requirements.

  1. Readability

OOP code often aligns with real-world concepts, making it easier to understand and model. Since we use classes and objects to represent tangible entities, mirroring ones in real life, it makes writing code more intuitive for developers and easier to grasp.

  1. Security

Since encapsulation engulfs the internal data and helps protect its integrity by controlling access to sensitive information through well-defined interfaces, it means that OOP in Java is a secure environment. This encapsulation process reduces the risk of unauthorised modifications and enhances security.

  1. Problem Solving:

OOP encourages a structured approach to problem-solving by breaking down problems into interacting objects, which leads to more efficient and organised solutions to errors that arise.

  1. Collaboration:

Since you can use classes in numerous projects, this promotes teamwork by allowing multiple developers to work separately on different parts of a project, as long as they adhere to the defined interfaces. Additionally, this benefit improves productivity and facilitates code sharing.

Disadvantages of OOP in Java

Object-oriented programming in Java has varied disadvantages, and we can sum them up in the following points.

  1. Steeper Learning Curve

While reading about OOP concepts like classes, objects, inheritance, and polymorphism seems simple, it can be challenging for beginners to grasp these concepts easily compared to procedural programming. OOP requires a shift in thinking to model problems into objects and their interactions. Programmers who once used procedural languages to write code may need time to adapt to OOP thinking.

  1. Overhead and Performance Impact

Using OOP in Java can increase memory usage and introduce overhead of the execution speed. Moreover, creating and managing objects and using polymorphism can add some overhead compared to simpler procedural code. This extensive effect on system resources might cause problems for performance-critical applications.

  1. Potential for Over-Engineering

Over-engineering translates to overly complicated code due to the excessive use of inheritance and complex class hierarchies. It also means that over-designing object models can make code harder to understand and maintain. For these reasons, it’s vital to strike a balance between flexibility and simplicity in OOP design.

  1. Tight Coupling

Tight coupling refers to the close-knit integration between classes due to improper use of inheritance, resulting in difficulty in making changes. If we create more subclasses from these complex superclasses, we create more problems that make it harder to modify classes independently. For this reason, it’s important to use design and interfaces carefully to mitigate this issue.

  1. Not Suitable for All Problems

Despite its comprehensive and easy-looking image, OOP is not a universal solution for every problem. This fact means that procedural or functional programming paradigms can sometimes solve problems better than OOP. For example, simple algorithms or data processing tasks might not benefit significantly from OOP overhead.

  1. Debugging Challenges

It can be difficult to debug OOP code due to the interactions between objects and the dynamic nature of polymorphism. While encapsulation makes it easier to identify and solve error locations, if we overuse inheritance, we require a deeper understanding of object relationships to trace those errors and solve them.

  1. Design and Implementation Challenges

Effective OOP design requires carefully planning and modelling real-world entities into classes and objects. This highlights the need for clear interfaces, manageable dependencies and avoiding overly-complex hierarchies. Such requirements mean that poorly designed OOP code can be difficult to maintain and extend.

  1. Potential for Memory Leaks

The extensive use of inheritance and polymorphism can result in large object graphs, which might lead to memory leaks. To avoid any memory-related problems, paying enough attention to object lifecycles and proper garbage collection processes is crucial.

Object-Oriented Programming in Java offers a powerful and efficient way to design and develop software while promoting code organisation and flexibility. Whether you’re just starting your programming journey or looking to enhance your skills, understanding OOP in Java is essential for career seekers and developers alike.


Why should I learn object-oriented programming in Java?

Learning object-oriented programming in Java can help you develop practical software development skills, as it is widely used in industry. It also promotes code reusability, modularity, and maintainability.

How do I create objects and use them in my Java program?

To create objects in your Java program, you must first define a class by specifying its properties (variables) and behaviours (methods). You can then instantiate objects from this class using the “new” keyword, assigning them to variables or directly using them.

Can you give me an example of how object-oriented programming works in Java?

Certainly! Let’s take the example of a car: we can define a Car class with properties such as colour, brand, and speed; methods like accelerate() or brake(); then we can create multiple Car objects from this class with different colours or brands but sharing similar behaviours.

Should I learn Phyton or Java first?

Even though Java is one of the most widely used programming languages, a number of beginner programmers find it more difficult to learn than Phyton, programmers stated they learned Phyton faster than they did Java.

Which language is 100% OOP?

Java is an ideal OOP environment due to its portability, powerful elements and its incredible application of its motto to write code once and run it anywhere. These elements make Java’s development ecosystem excellent for OOP.

Leave a comment

Your email address will not be published. Required fields are marked *