What defines an abstract class in Java?

• A. A class that can be instantiated
• B. A class that cannot contain methods
• C. A class that cannot be instantiated and may include abstract methods
• D. A class that provides concrete implementations of all methods

Answer: (C)

An abstract class in Java is defined as a class that cannot be instantiated directly and may include abstract methods, which are methods without an implementation. This means you cannot create an object of an abstract class; instead, you use it as a base to derive subclasses that provide the implementation of the abstract methods.

Abstract classes provide a way to define a common template for derived classes. They can include a mix of abstract methods (which must be implemented by any concrete subclass) and concrete methods (which have an implementation). This allows you to define behavior that all subclasses should inherit while still enabling them to have their own specific implementations for the abstract methods.

By contrast, a class that can be instantiated directly would not serve the purpose of an abstract class. Similarly, a class that cannot contain methods or one that provides concrete implementations for all methods would not be classified as an abstract class. These aspects emphasize the unique role of abstract classes in supporting polymorphism and code reusability in object-oriented programming.