Encapsulation

In the context of Object-Oriented Programming (OOP), encapsulation is one of the four fundamental principles (along with inheritance, polymorphism, and abstraction). It refers to the bundling of data (attributes or properties) with the methods (functions or behaviors) that operate on that data into a single unit, known as a class.

Key Concepts

• Bundling: Encapsulation groups related data and functions together as a single entity. For example, a Car class would bundle data like color, speed, and fuelLevel with methods like startEngine(), accelerate(), and refuel().
• Information Hiding (or Data Hiding): This is a crucial part of encapsulation. It involves restricting direct access to an object's internal state. This is typically achieved using access modifiers (public, private, protected). The internal data is usually kept private, while a controlled set of public methods (often called getters and setters) is provided to interact with that data. This prevents external code from accidentally or maliciously putting the object into an inconsistent or invalid state.

Example (in Java)

public class BankAccount {
    // Private data: hidden from outside the class
    private double balance;

    public BankAccount(double initialBalance) {
        if (initialBalance > 0) {
            this.balance = initialBalance;
        }
    }

    // Public method (getter) to access the balance safely
    public double getBalance() {
        return this.balance;
    }

    // Public method (setter) to modify the balance with validation
    public void deposit(double amount) {
        if (amount > 0) {
            this.balance += amount;
        }
    }

    // Public method to withdraw with validation
    public void withdraw(double amount) {
        if (amount > 0 && this.balance >= amount) {
            this.balance -= amount;
        } else {
            System.out.println("Withdrawal failed due to insufficient funds or invalid amount.");
        }
    }
}

In this example, the balance variable is private. You cannot access it directly from outside the BankAccount class. Instead, you must use the public methods getBalance(), deposit(), and withdraw(), which provide a safe and controlled interface to the object's state.