Abstract Classes vs. Interfaces: When Should I Use Each?

When to Opt for Abstract Classes or Interfaces

Abstract classes and interfaces are invaluable tools in object-oriented programming, allowing developers to define contracts and enforce behavior across classes. Here are the nuances that distinguish their usage:

Interfaces

Interfaces serve a specific purpose: they declare the methods and members that a class must implement. By implementing an interface, a class commits to providing implementations for all its methods. Interfaces enforce a contract that cannot be overridden in subclasses, ensuring consistency and adherence to the expected behavior.

Abstract Classes

In contrast, abstract classes provide a more flexible approach. They not only declare methods and members that must be implemented by subclasses but also provide default implementations. Subclasses can inherit these default implementations or override them to customize the behavior. Abstract classes offer a balance between enforcing behavior and allowing flexibility for specific implementations.

Making the Choice

Ultimately, the decision between using an abstract class or an interface depends on the desired level of rigidity and flexibility. If the goal is to define a strict contract that cannot be altered, an interface is the best choice. If some flexibility is required, while still enforcing a minimal set of behavior, an abstract class is more appropriate. Additionally, a class can implement multiple interfaces but can only extend a single class, regardless of whether it is abstract or not.

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