Encapsulation vs Abstraction

✅ 1. Encapsulation

Definition:
Encapsulation is the practice of hiding internal state and requiring all interaction to be performed through an object’s methods.

Goal:
Protect the internal state of the object from unintended or harmful modifications — data hiding.

How:

• Use private fields.
• Expose public/protected getter/setter or methods for controlled access.
• Prevent direct access to internal data structures.

Example:

public class BankAccount {
    private double balance; // encapsulated

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

    public double getBalance() {
        return this.balance;
    }
}

You can’t directly modify balance, only via methods that enforce business rules. That's encapsulation.

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✅ 2. Abstraction

Definition:
Abstraction is the process of hiding complexity by exposing only the relevant details of an object or system.

Goal:
Reduce complexity for the user of the system. Focus on what an object does, not how it does it.

How:

• Use interfaces or abstract classes.
• Model real-world behaviors with only necessary details.

Example:

public interface PaymentProcessor {
    void processPayment(double amount);
}

public class StripePaymentProcessor implements PaymentProcessor {
    public void processPayment(double amount) {
        // Stripe-specific API integration
    }
}

Client code doesn’t care how payment is processed, just that processPayment() is available. That's abstraction.

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🔍 Key Differences Table

Aspect	Encapsulation	Abstraction
Purpose	Hide internal data and enforce rules	Hide implementation complexity
Focus	How data is accessed/modified	What operations are exposed to the user
Implemented using	Access modifiers (private, public, etc.)	Interfaces, abstract classes, polymorphism
Goal	Data protection	Simplify usage
Example	Private fields with getters/setters	Interface hiding implementation

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🧠 Analogy

• Encapsulation: Think of a capsule — it wraps the medicine (data) inside a shell (methods). You don’t access the content directly.
• Abstraction: Think of a car. You drive using the steering wheel and pedals (interface) without knowing how the engine or transmission works (implementation).

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