DEV Community

Angela Gupta
Angela Gupta

Posted on


OOPs Concepts in Java

OOPs (Object-Oriented Programming) refers to a style of programming characterized by identifying classes of the objects defined that are closely linked with the associated methods/functions. OOPs, are associated with the concepts like class, object, Abstraction, Inheritance, encapsulation, and polymorphism. The most popular programming languages follow the OOP paradigm like Java, Ruby, C++, C#, etc.

Java is one of the most popularly known programming languages and is the most advanced computing platform. It had a humble beginning, which is now escalated to a powerful language with a significant share in today’s world. Java Programming language has successfully provided a reliable platform for developing many valuable services and applications. Many innovative products and digital services are dependent on Java for successful design implementation. Java is an integral part of developers’ career life as they have to create many products, services, and websites. There are also some websites that can’t be run without the involvement of Java. Thus, programmers should invest their time learning Java and exploring its in-demand features.

What are OOPs in Java?

Object-Oriented Programming (OOP) is a type of programming used by programmers to define the data structure with the help of data types and various operations that can be applied. Java is the most sought-after skill, and it is exciting to learn about OOPs concepts in Java. Talking about the object-based applications in Java depend on defining the classes, creating objects from these classes, and interacting between the created objects. There are four basic principles, or you can say the building blocks of OOP, that you must be aware of.

  • Inheritance
  • Encapsulation
  • Abstraction
  • Polymorphism

Let us look into these four principles in detail.

The Four Pillars of OOPs

OOPs 4 pillars


In OOPs, the programs are designed in a way where everything is an object, and these objects interact with one another. Inheritance, as the name suggests, you can inherit the properties of a class to another. The inheritance concept allows you to reuse the code and establish connections between multiple classes. Based on the inheritance concept, you can classify the classes into two categories:

  1. Parent Class - Super or Base class
  2. Child Class - Subclass or Derived class

A class that inherits the properties from a pre-defined class is known as the Child Class, and the class from whom these properties are inherited is known as the Parent Class.

Inheritance is further divided into four types:

Single Inheritance

Single Inheritance comes into the picture when a child class inherits the properties and behavior of a single parent class. This aids in the code reusability and adds new features to the existing code in the child class.

Multilevel Inheritance

The name itself suggests that there are multiple levels of Inheritance involved. Multilevel Inheritance appears when a child class inherits the properties and behaviors of parent classes at different levels.

Hierarchical Inheritance

It is a kind of Inheritance where a class has more than one child class - subclasses, or in simple words, multiple child classes have the same parent through which they inherit their properties and behaviors. Such kind of Inheritance indicates a Hierarchical Inheritance.

Hybrid Inheritance

A combination of multiple inheritances and multilevel Inheritance leads to a Hybrid Inheritance. Java doesn’t support multiple inheritances as it leads to ambiguity. Thus, Hybrid Inheritance can only be achieved with the help of the interfaces.


Encapsulation is a method that binds the data and the code together to form a single unit. This also paves the way for safeguarding your data from unnecessary modifications. Encapsulation allows methods and variables of a class to be well hidden and keep it safe. You can enable encapsulation in Java through the following methods:

  • Declare the variables of a class as private.
  • Enabling public getter and setter methods for modifying and viewing the variable values.


Abstraction focuses on events rather than the ideas that lead to the events. Abstraction helps hide the implementation details and only shows the output of these implementations that are essential things for a user. You can look at any website, and you will only get to see an attractive user interface rather than the hundred and thousand lines of code. You will not be aware of the internal processing but will be able to deal with its output, and that’s the beauty of Abstraction. Therefore, it helps in reducing the complexity. You can achieve Abstraction through two methods called,

Abstract Class

You use the ‘abstract’ keyword to implement an abstract class in Java. You can’t create an object of a class if it is declared an abstract class, and these classes can have abstract as well as concrete methods. You can make use of an abstract class by inheriting it from another class where you have defined and implemented the abstract methods.


You can refer to the interface as a class blueprint or a collection of abstract methods and static constants. Each method in the interface is public and abstract without any constructors. Interface and Abstraction contribute to achieving multiple inheritances in Java.


Polymorphism indicates many forms. Poly here means many, and morph means forms. Polymorphism indicates the ability of an object, function, or variables to showcase multiple forms. Through polymorphism, you can define one method or an interface and have multiple implementations. Polymorphism in Java is categorized into two:

Run time Polymorphism

Run time polymorphism in Java refers to a process where a call to an overridden method is resolved at the run time. This process involves using a reference variable to call an overridden method of a superclass at a run time.

Compile-time Polymorphism

Compile-time polymorphism in Java refers to a process where a call to an overloaded method is resolved at compile time. You can consider Method Overloading as an example of compile-time polymorphism.

Benefits of OOPs in Java

  • Faster development speed
  • Lesser development costs
  • Enhanced productivity during software development
  • Improved software maintainability
  • High-quality software

Summing Up

Many developers prefer Java programming for implementing various challenging projects. OOPs concepts in Java has proven to be one of the most cherished concepts as it has rewarded programmers with higher benefits and better performances. If you aim to build your career as a successful programmer and a developer, it is better to learn OOPs Concepts in Java as it’ll prove beneficial in your career journey. You can enroll in Great Learning’s OOPs Concepts in Java free course explicitly designed for beginners and covers all the OOPs concepts with examples and hands-on sessions.

Top comments (0)