ITPEC FE Morning October 2019 Question 47

Inheritance — a subclass takes over the attributes and methods defined in its superclass and can use them as its own.

In object orientation, a subclass is defined as a specialisation of an existing class. Through inheritance it gets the superclass's attributes and methods without redefining them, and adds or changes only what differs. For example, a SavingsAccount subclass of Account inherits balance and deposit() and adds an interest rate. Common features are written once, in the superclass, and reused.

Answer (b)

Why not others:

• •(a) Encapsulation — bundling data with the methods that operate on it and hiding the internals behind an interface
• •(c) Override — a subclass redefines an inherited method with the same name and signature; it replaces the superclass's behaviour rather than simply using it
• •(d) Polymorphism — the same message produces different behaviour depending on the class of the object that receives it

Key rule: Inheritance reuses superclass features, overriding changes an inherited method, polymorphism lets one call behave differently per class, and encapsulation hides the inside.

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