The first thing you’ll learn, when you start taking Java classes, is the OOPS principles in Java. These principles are the foundation of Java object-oriented programming concepts.
If you have a good understanding of them, you’ll be not coding — you’ll be building clean, reusable, scalable software like the pros do.
What is OOPS in Java?
- OOPS means Object-Oriented Programming System.
- In Java, OOP allows us to model real-world problems, with objects (things) and classes (the blueprint).
- Java is a pure OOP programming language because all of Java is based on classes and objects.
The 4 Core OOPS Principles in Java
When people talk about Java object oriented programming concepts, they’re usually referring to four main pillars:
- Encapsulation
- Abstraction
- Inheritance
- Polymorphism
Let’s break these down one by one, with easy explanations and code examples.
1. Encapsulation in Java
Definition:
Encapsulation is wrapping data (variables) and code (methods) together into a single unit.
In Java, we achieve encapsulation by:
- Declaring variables private
- Providing public getters and setters to access them
Example:
public class Student
{ private String name;
public String getName()
{
return name;
}
public void setName(String name)
{
this.name = name;
}}
Real-life analogy: Think of capsules in medicine — the medicine (data) is enclosed inside a protective shell (class), and you can only access it in controlled ways (methods).
2. Abstraction in Java
Definition:
Abstraction means hiding implementation, and only showing functionality.
We achieve abstraction in Java using:
- Abstract classes
- Interfaces
Example:
abstract class Vehicle
{
abstract void start();
}
class Car extends Vehicle
{
void start()
{
System.out.println("Car starts with a key.");
}}
Real-life analogy: When you drive a car, you only know how to start it — you don’t need to understand how the engine works.
3. Inheritance in Java
Definition:
Inheritance allows one class to inherit properties and methods from another class.
In Java, we use the extends keyword to implement inheritance in Java.
Example:
class Animal
{
void eat() {
System.out.println("This animal eats food.");
}}
class Dog extends Animal
{ void bark()
{
System.out.println("Dog barks.");
}}
Real-life analogy: Just like a child inherits traits from parents, a subclass inherits characteristics from a superclass.
4. Polymorphism in Java
Definition:
Polymorphism means many forms. In Java, polymorphism allows the same method to behave differently depending on the object.
Types:
- Compile-time polymorphism (Method Overloading)
- Runtime polymorphism (Method Overriding)
Example:
class Calculator
{
int add(int a, int b)
{
return a + b;
}
double add(double a, double b)
{
return a + b;
}}
Real-life analogy: A single word like “run” can have different meanings — athletes run, programs run, and engines run.
Why OOPS Principles in Java Matter
Understanding these Java object oriented programming concepts helps you:
- Write reusable code
- Improve maintainability
- Reduce redundancy
- Build scalable applications
Real-World Example of All OOP Principles Together
abstract class Employee
{
private String name; // Encapsulation
public Employee(String name) {
this.name = name;
}
public abstract void work(); // Abstraction
public String getName() {
return name;
}}
class Developer extends Employee {
public Developer(String name) {
super(name);
}
public void work() { // Polymorphism
System.out.println(getName() + " writes code.");
}}
class Manager extends Employee {
public Manager(String name) {
super(name);
}
public void work() {
System.out.println(getName() + " manages the team.");
}}
public class Company {
public static void main(String[] args) {
Employee dev = new Developer("Alice");
Employee mgr = new Manager("Bob");
dev.work();
mgr.work();
}}
FAQs About OOPS Principles in Java
Q1: Is Java an Object Oriented Programming language?
Not really – Java has primitives like int and char that are valuable data types but don’t classify as an object.
Q2: What is the most valuable OOPs concept?
They are all valuable but encapsulation and abstraction give security and design to your code.
Q3: How do OOPs principles help you code?
They make your code modular, maintainable, and reusable.
Final Thoughts
If you genuinely would like to pursue your dream to be a java professional developer, then you can’t avoid learning “oops principles in java” and “java object oriented programming“.
Oops principles in java are not just theories, but they are the real-world way of developing Java applications. Start implementing them in your java projects today, and you will be amazed at the difference in code quality, scalability and maintainability.
If you want to increase your foundation of learning from starting to advanced, you might consider an organized java course, that teaches everything from the basic parts of java to full stack and advanced java object oriented programming concepts with real projects. An organized and well-structured java development course will not only enhance your understanding of OOPS, but also prepares you for a job interview and working as a professional software development.
