Can an abstract class contain concrete methods?

An abstract class can indeed contain both abstract and concrete methods, making it possible to provide a mix of both functionalities within a single class definition. Concrete methods are fully defined, meaning they have an implementation that can be used directly, while abstract methods are declared without implementations and must be implemented by any subclass that derives from the abstract class.

This flexibility allows developers to define a common base class that includes shared functionality (through concrete methods) while also imposing requirements on subclasses to provide specific implementations for various behaviors (through abstract methods). For instance, an abstract class might provide a utility method for handling common tasks, while leaving specific methods that vary across subclasses abstract.

The option stating that it can only have abstract methods is incorrect because it overlooks the ability of abstract classes to provide concrete methods alongside their abstract declarations. The mention of an abstract class being final does not affect its capacity to contain concrete methods, as a final class simply cannot be subclassed. Similarly, stating that it must only declare the methods ignores the key feature of abstract classes as a mechanism to provide shared code and behavior.