OOPS Concepts in Java: Object-Oriented Programming System (OOPS) in Java revolves around four key principles known as the OOPS concepts in JAVA. Encapsulation involves bundling data and methods into a single unit, promoting data hiding. Inheritance allows a class to inherit properties and behaviours from another, fostering code reusability. 

Polymorphism enables objects to take on multiple forms, allowing flexibility in method invocation. Abstraction simplifies intricate systems by creating models of classes from real-world things. It highlights crucial aspects and conceals unnecessary details.

These OOPS concepts in Java collectively form the foundation of Java programming, facilitating modular, maintainable, and extensible code development.

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Also read: Object Oriented Programming In Java Specialization, Java OOP Tutorial

What Are the OOPS Concepts in Java?

OOP organises software into objects, each symbolising a real-world entity or idea. Java’s design relies on OOP, embodying four key principles: Encapsulation, Inheritance, Polymorphism, and Abstraction.

• Encapsulation: Encapsulation involves bundling data (attributes) and methods (functions) that operate on the data into a single unit, known as a class. This unit restricts access to some of its components, providing a protective barrier that prevents the accidental modification of data. The outside world interacts with the class through a well-defined interface, promoting data security and code maintainability.

• Inheritance: Inheritance is a mechanism that allows a class (subclass or child class) to inherit properties and behaviours from another class (superclass or parent class). This promotes code reusability, as common functionalities can be defined in a base class and shared among derived classes. In Java, the “extends” keyword is used to establish inheritance relationships between classes.

• Polymorphism: Polymorphism means “many forms” and is a concept that allows objects to take on multiple forms. In Java, polymorphism is accomplished by using method overloading and method overriding. Method overloading means creating several methods with the same name but different parameters. In contrast, method overriding allows a subclass to provide a specific implementation of a method defined in its superclass. This flexibility simplifies code design and supports dynamic method invocation.

• Abstraction: Abstraction involves simplifying complex systems by modelling classes based on real-world entities and focusing on essential features while hiding unnecessary details. Abstract classes and interfaces in Java are key components of abstraction. Abstract classes provide a blueprint for other classes and can contain both abstract (unimplemented) and concrete (implemented) methods. Interfaces define a contract for classes to implement, promoting a standardised way to interact with diverse objects.

• Coupling: Coupling refers to the knowledge or information or dependency of another class. It arises when classes are aware of each other. If a class has the detailed information of another class, there is strong coupling. In Java, we use private, protected, and public modifiers to display the visibility level of a class, method, and field. You can use interfaces for the weaker coupling because there is no concrete implementation.

• Cohesion: Cohesion refers to the level of a component that performs a single well-defined task. A single well-defined task is done by a highly cohesive method. The weakly cohesive method will split the task into separate parts. The java.io package is highly cohesive because it has I/O related classes and interface. However, the java.util package is a weakly cohesive package because it has unrelated classes and interfaces.

• Association: Association represents the relationship between the objects. Here, one object can be associated with one object or many objects. There can be four types of association between the objects:

• One to One
• One to Many
• Many to One, and
• Many to Many

Let’s understand the relationship with real-time examples. For example, One country can have one prime minister (one-to-one), and a prime minister can have many ministers (one to many). Also, many MP’s can have one prime minister (many to one), and many ministers can have many departments (many to many).

• Aggregation: Aggregation is a method to attain Association. It shows the connection where one object holds other objects as a part of its condition. It reflects a not-so-strong relationship between objects. In Java, it is also called a has-a relationship, similar to how inheritance shows the is-a relationship. It provides another way to recycle objects.
• Composition: Composition is also a method to achieve Association. Composition illustrates the connection where one object holds other objects as a part of its condition. There exists a robust relationship between the holding object and the dependent object. It is a situation where holding objects cannot exist independently. If you remove the main object, all the associated objects will be automatically removed.

Why is it Called an Object-Oriented Programming Language?

The most commonly used OOP languages are based on classes, signifying that objects are examples of classes, which also define their types. The terms “objects” and “oriented” were first employed in the modern sense of object-oriented programming.

Java stands out as the widely embraced pure object-oriented language. Developed by Sun Microsystems, it served as a control language for small appliances. It was well-suited for use with many languages that allow object orientation. PASCAL has transformed into the object-oriented DELPHI. C supports object orientation without making it mandatory.

Not all techniques and structures associated with object-oriented programming are directly supported in languages claiming OOP support. It performs operations on numbers. The features mentioned below are typical in languages supporting object-oriented programming.

Languages with the majority of object features are original. Oberon or Oberon-2 are examples. It is possible to use abstract data type support in languages that do not have all of the features of object-orientation. object-orientation. This also includes prototype-based languages. prototype-based languages. Javascript, Lua, and CLU are examples.

Also read: Full Form of OOPS: Applications, Advantages, Future Trends

Difference Between Procedural and Object-Oriented Programming

Procedural and object-oriented programming may look similar to you. However, in reality, they differ a lot from each other. We have explained the differences between both in detail in the table below:

Advantages of OOPs Over Procedure-Oriented Programming Language

Here are some advantages of OOPS over procedure-Oriented programming language:

• Object-oriented programming (OOP) simplifies both development and upkeep tasks.

• It ensures data concealment, allowing the simulation of real-world events more effectively. 

• OOP’s execution is faster and more straightforward.

• It establishes a clear program structure and promotes the “Don’t Repeat Yourself” (DRY) principle.

• OOP enables the creation of fully reusable applications with less code and shorter development time.

• OOP helps to keep the code DRY “Don’t Repeat Yourself”.

• Its modularity facilitates easier troubleshooting, and it provides flexibility through polymorphism, leading to enhanced productivity.

• Modularity for easier troubleshooting.

• OOP gives flexibility through polymorphism.
• OOP gives better productivity.

We have looked at some of the main OOPS concepts in Java in this article. Having a good understanding of these OOPS Concepts in Java is essential if you want to use them well and write good code.

Also read: OOPs Concepts in Java with Examples & Interview Questions