Encapsulation

Encapsulation is one of the four main pillars of Object-Oriented Programming (OOP).

It refers to wrapping the data (variables) and the code (methods) that works on the data into a single unit- a class.

But most importantly, it restricts direct access to internal data using access modifiers (like private, public, etc.).

🧠 Think of it like...

A capsule or medicine bottle:

• The medicine (data) is hidden inside

• You access it only through a prescription (methods)

🔸 Example Without Encapsulation:

class Account {
    public int balance;  // not secure

    void displayBalance() {
        System.out.println("Balance: " + balance);
    }
}

public class Main {
    public static void main(String[] args) {
        Account acc = new Account();
        acc.balance = -5000;  // anyone can assign wrong value!
        acc.displayBalance();
    }
}

This is bad practice because:

• balance can be changed directly

• Negative or invalid values can be assigned

• No control over how data is used

🔒 Proper Encapsulation (Best Practice)

class Account {
    private int balance = 0;  // data hidden

    public void setBalance(int amount) {
        if (amount >= 0) {
            balance = amount;
        } else {
            System.out.println("Invalid balance.");
        }
    }

    public int getBalance() {
        return balance;
    }
}

public class Main {
    public static void main(String[] args) {
        Account acc = new Account();
        acc.setBalance(5000);                            // safe
        System.out.println("Balance: " + acc.getBalance());
    }
}

Balance: 5000

🔒 Why Encapsulation Is Important

🔓 Access Modifiers Recap

In encapsulation, we typically use:

• private for variables

• public for getter/setter methods