Understanding Object-Oriented Programming in Java

Object-Oriented Programming (OOP) is a fundamental paradigm in Java. This guide covers the four pillars of OOP and how to apply them effectively.

The Four Pillars of OOP

1. Encapsulation

Encapsulation bundles data and methods together, hiding internal details:

java
public class BankAccount {
    private double balance;

    public void deposit(double amount) {
        if (amount > 0) {
            balance += amount;
        }
    }

    public double getBalance() {
        return balance;
    }
}

2. Inheritance

Inheritance allows classes to inherit properties from parent classes:

java
public class Animal {
    public void eat() {
        System.out.println("Eating...");
    }
}

public class Dog extends Animal {
    public void bark() {
        System.out.println("Woof!");
    }
}

3. Polymorphism

Polymorphism allows objects to take many forms:

java
public class Shape {
    public double area() {
        return 0;
    }
}

public class Circle extends Shape {
    private double radius;

    @Override
    public double area() {
        return Math.PI * radius * radius;
    }
}

4. Abstraction

Abstraction hides complexity while showing only essential features:

java
public abstract class Vehicle {
    abstract void start();

    public void run() {
        start();
        System.out.println("Vehicle is running");
    }
}

Benefits of OOP

• Code reusability
• Modularity
• Easy troubleshooting
• Data hiding for security