ITPEC FE Morning October 2019 Question 9

A subclass provides its own implementation of a method its superclass already has — that is overriding, and it is what makes polymorphism work.

The overriding method keeps the same name and signature but replaces the body. When code calls the method through a superclass reference, the version in the object's actual class runs, chosen at run time. One call therefore behaves differently for different kinds of object.

Answer (a)

Why not others:

• •(b) — generalization: collecting the common properties of several classes into a superclass; it builds the hierarchy that overriding then works on
• •(c) — overloading: methods with the same name but a different number, type or order of arguments, chosen at compile time from the arguments
• •(d) — encapsulation (information hiding): keeping an object's internal structure out of its external specification

Key rule: Same name and same signature in a subclass is overriding, chosen at run time; same name with different parameters is overloading, chosen at compile time.

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