Abstract Classes

### Giai đoạn: Nền Tảng & Khái Niệm Cốt Lõi **Abstract Classes** An abstract class is a restricted base class that cannot be used to create objects. It serves as a blueprint for other classes, providing a common structure by defining methods that subclasses must implement. While it can contain fully functional methods, its primary purpose is to enforce a consistent interface and shared behavior across related objects in a system. ### Khái niệm cốt lõi: 1. **An abstract class is a restricted base class that cannot be used to create objects** ### Tài liệu tham khảo chính thống: - [What is an Abstract Class in Object Oriented Programming](https://www.theserverside.com/definition/abstract-class) (article)