25 Oct 2023
Beginner
Here's a table highlighting the key differences between abstraction and interface in object-oriented programming (OOP):
| Aspect | Abstraction | Interface |
|---|---|---|
| Purpose | To define a common base class with some methods and leave the implementation details to the derived classes. | To define a contract or a set of method signatures that a class must implement. |
| Implementation | Abstract classes can have both abstract (unimplemented) and concrete (implemented) methods. | Interfaces can only declare method signatures, leaving the implementation to the implementing class. |
| Inheritance | Abstract classes can be extended using inheritance by using the "extends" keyword. | Interfaces are implemented using the "implements" keyword and can be implemented by multiple classes. |
| Multiple Inheritance | A class can extend only one abstract class (single inheritance). | A class can implement multiple interfaces (multiple inheritance of method signatures). |
| Constructor | Abstract classes can have constructors. | Interfaces cannot have constructors. |
| Variables | Abstract classes can have instance variables (fields). | Interfaces can only have constant (static final) variables. |
| Code Reusability | Provides a way to reuse code through inheritance. | Promotes code reusability through the implementation of multiple interfaces. |
| Flexibility | Offers a balance between providing a base class structure and allowing flexibility for derived classes. | Provides a strict contract that implementing classes must adhere to, which enforces consistency. |
| Usage | Used when you have a common base class with some shared functionality and some abstract methods to be implemented by derived classes. | Used when you want to define a contract that multiple classes must follow, often to ensure compatibility or to define specific behavior. |
It's important to note that in some programming languages, such as Java, a class can both extend an abstract class and implement one or more interfaces. This allows for a combination of the benefits of both abstraction and interface.
