🌟 When to Use Abstraction and Interface in Java
🔹 Use an Abstract Class when:
| Scenario | Why Use It |
|---|---|
| You want to provide a base class with some shared code and partial implementation | Abstract classes can have both implemented and unimplemented methods |
| You need non-static fields, constructors, or maintain state | Interfaces can’t have constructors; abstract classes can |
| You want to control inheritance | Abstract class supports single inheritance only, making design easier to manage |
🔹 Use an Interface when:
| Scenario | Why Use It |
|---|---|
| You need to enforce a contract that multiple unrelated classes can implement | Interfaces promote multiple inheritance of type |
| You want to achieve polymorphism across class hierarchies | Interfaces allow unrelated classes to be treated uniformly |
| You’re building a plug-and-play API or dependency injection system | Interfaces keep things loosely coupled and easily swappable |
🧠 Final Takeaways
- Use abstract classes when you need a base class with shared code and structure.
- Use interfaces when you want a common contract across unrelated classes.
- You can use both together: a class can extend an abstract class and implement multiple interfaces for flexibility.
- Think of it like this:
- Abstract Class = “is-a” base with shared behavior
- Interface = “can-do” capability
