Java supports several other modifiers besides the access modifiers. These modifiers are covered in the following subsections.
abstract and final Neither abstract classes nor abstract methods can be declared as final.
The abstract modifier is used to identify abstract classes and methods. An abstract class defers its implementation to its subclasses and cannot be instantiated. Abstract classes provide a way to enforce a class design and hierarchy without requiring a particular implementation.
abstract Subclasses If a class extends an abstract class, then it must implement all methods declared as abstract, if any, or be declared as abstract.
Abstract classes can declare abstract methods. An abstract method is ...