Java’s OOPs is built on four pillars: <\/p>\n\n\n\n
- \n
- Encapsulation<\/strong> hides your data and controls access. <\/li>\n\n\n\n
- Inheritance<\/strong> lets classes reuse code from a parent class. <\/li>\n\n\n\n
- Polymorphism<\/strong> allows one method to behave differently based on context.<\/li>\n\n\n\n
- Abstraction<\/strong> hides complexity and exposes only what’s necessary. <\/li>\n<\/ul>\n\n\n\n
What is OOPs (Object-Oriented Programming) in Java?<\/strong><\/h2>\n\n\n\n
Object-Oriented Programming (OOPs) in <\/strong>Java<\/strong><\/a> is a programming paradigm that organizes code around objects<\/strong> and classes<\/strong> rather than functions and logic alone. Java is one of the most widely used OOPs languages in the world, and its entire ecosystem, from Spring Boot to Android, is built on OOPs principles.<\/p>\n\n\n\n
OOPs makes your code more modular, reusable, secure, and easier to maintain<\/strong>. Instead of writing one giant block of instructions, you model your program around real-world entities (objects) that have properties (data) and behaviors (methods).<\/p>\n\n\n\n
\ud83d\udca1 Did You Know?<\/strong>
Java<\/b> isn’t considered 100% object-oriented; it still uses primitive data types like int, char, and boolean that aren’t objects. That’s a classic interview trap!<\/div>\n\n\n\n<\/p>\n\n\n\n
If you want to take this further and build full Java-based applications from the ground up with mentor guidance, then check out HCL GUVI’s Certified Java Full Stack Developer Course<\/a>. You’ll go from OOPs fundamentals all the way to deploying real-world projects and in the end you will be getting an industry-grade certification!<\/em><\/strong><\/p>\n\n\n\n
The 2 Building Blocks: Object and Class<\/strong><\/h2>\n\n\n\n
![\"The](\"https:\/\/www.guvi.in\/blog\/wp-content\/uploads\/2026\/03\/1-3.webp\" "\\"\\"")
<\/figure>\n\n\n\nEvery OOPs program in Java revolves around two core building blocks (Class and Objects<\/a>) before the four pillars even come into play.<\/p>\n\n\n\n
A Class<\/strong> is a blueprint. It defines what properties and behaviors an object will have, but it doesn’t occupy memory on its own. Think of it like an architectural drawing for a house.<\/p>\n\n\n\n
An Object<\/strong> is a real instance of that class, the actual house built from the blueprint. It lives in memory and has actual values.<\/p>\n\n\n\n
\/\/ Class = Blueprint\n\nclass Car {\n\n String brand;\n\n int speed;\n\n void accelerate() {\n\n System.out.println(brand + \" is accelerating at \" + speed + \" km\/h\");\n\n }\n\n}\n\n\/\/ Object = Real Instance\n\npublic class Main {\n\n public static void main(String[] args) {\n\n Car myCar = new Car(); \/\/ Creating an object\n\n myCar.brand = \"Toyota\";\n\n myCar.speed = 120;\n\n myCar.accelerate(); \/\/ Output: Toyota is accelerating at 120 km\/h\n\n }\n\n}<\/code><\/pre>\n\n\n\nSimple enough, right? Now let’s get to the four pillars that make OOPs truly powerful.<\/p>\n\n\n\n
If you are planning on learning OOPs through a structured self-paced course, then consider enrolling in HCL GUVI\u2019s Certified Object-Oriented Programming (OOPs) Course<\/a>, which is perfect for beginners looking to master OOPs fundamentals. It covers key concepts like classes, objects, inheritance, polymorphism, and design patterns.<\/em><\/strong><\/p>\n\n\n\n
The 4 OOPs Concepts in Java: Explained with Examples<\/strong><\/h2>\n\n\n\n
These four concepts are the heart of every Java interview<\/a>, every Java project<\/a>, and every Java framework you’ll ever work with. Let’s break each one down properly.<\/p>\n\n\n\n
1. Encapsulation: Protecting Your Data<\/strong><\/h3>\n\n\n\n
![\"Encapsulation:](\"https:\/\/www.guvi.in\/blog\/wp-content\/uploads\/2026\/03\/2-3.webp\" "\\"\\"")
<\/figure>\n\n\n\nEncapsulation in OOPs is all about keeping your data safe from outside interference<\/strong>. You wrap your data (fields) and the methods that operate on that data inside a class, then restrict direct access using access modifiers. External code can only interact with your data through controlled methods, called getters and setters<\/strong>.<\/p>\n\n\n\n
Think of it like your bank account. You can check your balance and withdraw money through the ATM, but you can’t directly reach into the bank’s database and change your balance. The data is encapsulated.<\/p>\n\n\n\n
In Java, encapsulation is achieved by:<\/p>\n\n\n\n
- \n
- Declaring class fields as private<\/li>\n\n\n\n
- Providing public getter and setter methods to read and update those fields<\/li>\n<\/ul>\n\n\n\n
class BankAccount {\n\n private double balance; \/\/ Hidden from outside world\n\n \/\/ Controlled access through getter\n\n public double getBalance() {\n\n return balance;\n\n }\n\n \/\/ Controlled update through setter\n\n public void deposit(double amount) {\n\n if (amount > 0) {\n\n balance += amount;\n\n }\n\n }\n\n}\n\npublic class Main {\n\n public static void main(String[] args) {\n\n BankAccount account = new BankAccount();\n\n account.deposit(5000);\n\n System.out.println(\"Balance: \" + account.getBalance()); \/\/ Balance: 5000.0\n\n \/\/ account.balance = 99999; \u2190 This would cause a compile error!\n\n }\n\n}<\/code><\/pre>\n\n\n\n
- Inheritance<\/strong> lets classes reuse code from a parent class. <\/li>\n\n\n\n
![\"Inheritance:](\"https:\/\/www.guvi.in\/blog\/wp-content\/uploads\/2026\/03\/3-3.webp\" "\\"\\"")
<\/figure>\n\n\n\n![\"Polymorphism\"](\"https:\/\/www.guvi.in\/blog\/wp-content\/uploads\/2026\/03\/5-1.webp\" "\\"\\"")
<\/figure>\n\n\n\n![\"Abstraction\"](\"https:\/\/www.guvi.in\/blog\/wp-content\/uploads\/2026\/03\/6.webp\" "\\"\\"")
<\/figure>\n\n\n\n