What is OOP in Java?

Object-Oriented Programming (OOP) is a programming paradigm based on the concept of objects, which can contain data (fields) and code (methods). Java is a fully OOP language.

Core Concepts of OOP in Java

1. Class

• A blueprint/template for creating objects.

• Defines properties (attributes) and behaviors (methods).

2. Object

• An instance of a class.

• Created using the new keyword.

Car myCar = new Car();
myCar.color = “Red”;
myCar.accelerate();

3. Encapsulation

• Wrapping data (variables) and methods into a single unit (class).

• Data hiding using access modifiers (private, public, etc.).

public class Person {
private String name;

public void setName(String n) {
name = n;
}

public String getName() {
return name;
}
}

4. Inheritance

• A class inherits properties and methods from another class.

• Promotes code reuse.

public class Animal {
void eat() {
System.out.println(“Eating…”);
}
}

public class Dog extends Animal {
void bark() {
System.out.println(“Barking…”);
}
}

5. Polymorphism

• Ability to take many forms.

• Method overriding and method overloading.

class Animal {
void sound() {
System.out.println(“Animal makes a sound”);
}
}

class Cat extends Animal {
@Override
void sound() {
System.out.println(“Meow”);
}
}

6. Abstraction

• Hiding complex implementation details and showing only essential features.

• Achieved with abstract classes and interfaces.

abstract class Shape {
abstract void draw();
}

class Circle extends Shape {
void draw() {
System.out.println(“Drawing Circle”);
}
}

Simple Example Putting It Together

class Employee {
private String name;
private int id;

public Employee(String name, int id) {
this.name = name;
this.id = id;
}

public void display() {
System.out.println(“Name: ” + name + “, ID: ” + id);
}
}

public class Main {
public static void main(String[] args) {
Employee emp = new Employee(“Alice”, 101);
emp.display();
}
}