AMCAT Object-Oriented Programming Concepts 3

Question 1

In OOP, 'composition' refers to:

Accepted Answer

A class being built from objects of other classes as parts

Answer

Composition is a 'has-a' relationship where one class contains references to objects of other classes as its components, building complex types from simpler ones.

Question 2

What is the key difference between aggregation and composition in OOP?

Accepted Answer

Composition implies stronger ownership where child objects cannot exist independently; aggregation is a weaker 'uses-a' relationship

Answer

In composition, the contained objects' lifecycle is tied to the container (strong ownership), while in aggregation the contained object can exist independently of the container.

Question 3

A virtual function in C++ is a member function that:

Accepted Answer

Is declared in the base class and overridden in derived classes, resolved at runtime

Answer

Virtual functions enable runtime polymorphism — the function to call is determined at runtime based on the actual object type, not the pointer or reference type.

Question 4

Which design pattern ensures that only one instance of a class is created throughout the application's lifetime?

Accepted Answer

Singleton Pattern

Answer

The Singleton pattern restricts instantiation of a class to exactly one object and provides a global point of access to that instance.

Question 5

Which of the following is a characteristic of a pure virtual function (in C++) or abstract method (in Java/C#)?

Accepted Answer

It must be overridden in every concrete subclass

Answer

A pure virtual / abstract method has no implementation in the base/abstract class and must be implemented by every concrete (non-abstract) derived class.

AMCAT Practice Test

AMCAT Practice Test

AMCAT Object-Oriented Programming Concepts 3