What is an abstract method?

• A. A method that is defined within an interface only.
• B. A method with no implementation provided in its definition.
• C. A method that cannot be overridden in subclasses.
• D. A method that needs to be final in subclasses.

Answer: (B)

An abstract method is specifically characterized as a method that has no implementation provided in its definition. Its primary purpose is to declare a method signature that subclasses are required to implement, ensuring that the subclasses provide their specific functionality. In Java, abstract methods are declared within abstract classes or interfaces, allowing developers to create a structure where certain behaviors must be defined by any non-abstract subclass.

Choosing this option underscores the concept of abstraction in object-oriented programming, which encourages the design of a common interface while letting specific implementations vary across different subclasses. This flexibility is a cornerstone of polymorphism, one of the fundamental principles of object-oriented design.

Options that suggest a method is defined only within an interface, cannot be overridden, or must be declared as final do not accurately capture the essence of what an abstract method is in the context of Java and its use in inheritance and polymorphism.