Which of the following statements is correct?
A) is-a and has-a relationships cannot be combined.
B) An abstract class can be instantiated.
C) An abstract class cannot declare abstract methods.
D) In Java, a variable of a superclass type can reference an object of a subclass type.

Question

Quizplus · Accepted Answer

In Java, polymorphism allows a variable of a superclass type to reference an object of a subclass type. This is a fundamental concept that enables the implementation of polymorphic behavior, where a single interface can be used to represent different underlying forms (types). Options A, B, and C are incorrect because: A) is-a (inheritance) and has-a (composition) relationships can indeed be combined in object-oriented design; B) An abstract class cannot be instantiated directly—it requires a concrete subclass to provide implementations for the abstract methods; C) An abstract class can declare abstract methods, which is one of the primary reasons for using abstract classes.

Which of the Following Statements Is Correct