AMCAT Object-Oriented Programming Concepts 1 — Questions and Answers
Question 1: Which OOP principle bundles data and methods that operate on that data within a single unit, restricting direct access from outside?
- Inheritance
- Polymorphism
- Encapsulation (Correct answer)
- Abstraction
Correct answer: Encapsulation
Encapsulation wraps data (attributes) and behavior (methods) together in a class and controls access through access modifiers like private, protected, and public.
Question 2: When a child class acquires the properties and behaviors of a parent class, this OOP concept is called:
- Polymorphism
- Encapsulation
- Abstraction
- Inheritance (Correct answer)
Correct answer: Inheritance
Inheritance allows a derived (child) class to reuse the fields and methods of a base (parent) class, promoting code reuse.
Question 3: Which of the following best describes polymorphism in OOP?
- A class can have only one constructor
- The same interface can be used for different underlying data types (Correct answer)
- A class cannot be instantiated
- All methods must be overridden
Correct answer: The same interface can be used for different underlying data types
Polymorphism means 'many forms' — the same method name or interface can behave differently depending on the object it operates on.
Question 4: What is an abstract class in object-oriented programming?
- A class with no attributes
- A class that can be directly instantiated
- A class that cannot be instantiated and may contain abstract methods (Correct answer)
- A class that inherits from multiple classes
Correct answer: A class that cannot be instantiated and may contain abstract methods
An abstract class serves as a blueprint for other classes; it cannot be instantiated on its own and may define abstract methods that subclasses must implement.
Question 5: Which of the following correctly distinguishes a class from an object?
- An object is a blueprint; a class is an instance
- A class is a blueprint; an object is an instance of that class (Correct answer)
- Classes and objects are the same thing
- An object can exist without a class
Correct answer: A class is a blueprint; an object is an instance of that class
A class defines the structure and behavior (blueprint), while an object is a concrete instance created from that class at runtime.
Question 6: Method overloading allows a class to define multiple methods with the same name but different:
- Return types only
- Access modifiers only
- Parameter lists (number or type of parameters) (Correct answer)
- Bodies only
Correct answer: Parameter lists (number or type of parameters)
Method overloading (compile-time polymorphism) requires methods to differ in their parameter list — either in the number, type, or order of parameters.
Question 7: In OOP, an interface is best described as:
- A class that has only private methods
- A contract specifying method signatures that implementing classes must define (Correct answer)
- A class that stores only static data
- A mechanism to restrict inheritance
Correct answer: A contract specifying method signatures that implementing classes must define
An interface defines a contract — it declares method signatures (and sometimes constants) without providing implementation, and any class that implements it must provide the bodies.
