Abstraction in Object-Oriented Programming (OOP)
What is Abstraction?
Definition
Abstraction
Abstraction is the process of hiding implementation details and exposing only the essential features of an object.
It allows programmers to focus on what an object does, not how it does it.
Hint
Think of it as using a car: you know how to drive it, but you don’t need to know how the engine works.
Why Abstraction Matters
- Simplifies Complexity
- Reduces the problem to its core functionality.
- Makes large systems easier to understand and manage.
- Modular Code
- Encourages development of independent modules.
- Improves readability and maintainability.
- Reusability & Extensibility
- Abstract classes and interfaces allow flexible reuse across multiple projects.
How Abstraction is Implemented
Abstract Classes
- Define common attributes and methods but leave some methods abstract (unimplemented).
- Subclasses provide specific implementations.
Example
Java:
abstract class Vehicle {
abstract void move();
}
class Car extends Vehicle {
void move() {
System.out.println("Car drives on the road.");
}
}Interfaces
- Define a contract (methods) that a class must implement.
- Allow multiple classes to share common behaviour without sharing code.
Encapsulation vs Abstraction
- Encapsulation: Restricts direct access to data (how data is stored).
- Abstraction: Hides implementation details (how actions are performed).
| Aspect | Abstraction | Encapsulation |
|---|---|---|
| Definition | Hides implementation details and shows only the essential features of an object. | Bundles data and methods together, restricting direct access to ensure data security. |
| Purpose | Focuses on what an object does. | Focuses on how data is accessed and modified. |
| Implementation | Achieved using Abstract Classes and Interfaces. | Achieved using Access Modifiers (public, private, protected) and getters/setters. |
| Level | Works at the Design Level - models the system structure. | Works at the Implementation Level - controls data handling. |
| Example (real-world) | Car driving: You use the steering wheel and pedals without knowing engine details. | Medical capsule: Medicine (data) is safely enclosed inside a protective shell. |
| Example (code) | abstract class Shape { abstract void draw(); } | private int age; public void setAge(int a) { age = a; } |
| Problem solved | Simplifies complex systems by hiding unnecessary details. | Provides data protection and prevents misuse. |
| Common exam mistake | Saying abstraction “hides data” (that’s encapsulation). | Thinking encapsulation “hides implementation” (that’s abstraction). |
Note
- Abstraction → What the object does.
- Encapsulation → How the object’s data is protected
Real-World Examples
- Bank ATM: Users can withdraw money without knowing the internal banking software.
- Smartphone: You use apps without understanding the underlying code.
- OOP Design: A Shape abstract class with subclasses Circle, Square, etc., each implementing draw().
Exam technique
- Use examples (ATM, vehicle, shapes) to explain abstraction.
- Always mention abstract classes or interfaces when asked about implementation.
- Contrast abstraction vs encapsulation - a common exam trick.
Common Mistake
- Confusing abstraction with encapsulation.
- Saying abstraction “hides data” (that’s encapsulation): instead, abstraction hides implementation details.
- Forgetting that abstract classes cannot be instantiated
