ITPEC FE Morning October 2023 Question 47

Which of the following is the most appropriate feature of polymorphism in object-oriented programming?

a)Developers are allowed to define classes incrementally by reusing classes defined previously as the basis for new classes.b)Only the information required to use a software module is published to the module user.c)The processes and data are combined into a single object.d)The same message can be interpreted differently by different classes of objects.

Explanation

The same message is interpreted differently by different classes of objects — that is polymorphism.

In object-oriented programming, several classes can implement the same method name in their own way. The sender only issues the message, for example draw(), and each receiving object (a Circle, a Square) runs its own version. The caller need not know the concrete class, so new classes can be added without changing the calling code. Overriding a superclass method in subclasses is the usual way to achieve this.

Answer (d)

Why not others:

•(a) — defining new classes by reusing existing classes as their basis describes inheritance
•(b) — publishing only what a user of the module needs describes information hiding
•(c) — combining processes and data into a single object describes encapsulation

Key rule: Inheritance reuses a class, encapsulation bundles data with methods, information hiding limits what is visible, and polymorphism lets one message produce class-specific behaviour.

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