Abstract and Final Methods and Classes

Using the ABSTRACT and FINAL additions of the METHODS and CLASS statements, you can define abstract and final methods or classes.

Abstract methods are declared in abstract classes and cannot be implemented in the same class but only in a subclass of the inheritance tree. Abstract classes can consequently not be instantiated.

Final methods cannot be redefined in subclasses. Final classes cannot have any more subclasses and constitute the final node of an inheritance tree.