TRB PG Assistant - Object Oriented Programming - class, object, encapsulation, inheritance, polymorphism, abstract classes One Line Questions & Answers

1. What is an abstract class in OOP? — A class that cannot be instantiated and may contain abstract methods.

2. A class that cannot be instantiated and is designed to be inherited from is typically: — An abstract class

3. What is a constructor in the context of a class? — A special method called automatically when an object is created.

4. What happens when you create an object from a class? — Memory is allocated for the object's data.

5. Which of the following best describes the concept of a 'class'? — A user-defined data type that defines properties and behaviors.

6. A class that contains only abstract methods and no concrete methods or instance variables is often called an: — Interface

7. Which OOP concept promotes code reuse by allowing classes to share common functionality? — Inheritance

8. What is the fundamental difference between an abstract class and an interface in many OOP languages? — An abstract class can have instance variables, while an interface cannot.

9. What is the relationship between a class and an object? — A class is a blueprint, and an object is an instance of that blueprint.

10. What are the actions or functions that an object can perform called? — Methods

11. A class that inherits from another class is called a: — Derived class

12. What is an instance of a class called in OOP? — Object

13. What is the primary benefit of encapsulation? — Data hiding and modularity

14. Which type of polymorphism allows a derived class to provide a specific implementation of a method that is already defined in its base class? — Runtime Polymorphism (Overriding)

15. The process of an object taking on the properties of another object is known as: — Inheritance

16. What is the term for a method defined in an abstract class that has no implementation? — Abstract method

17. A class from which other classes inherit is called a: — Base class

18. In OOP, inheritance allows a class to reuse code from another class. This promotes: — Reusability

19. In OOP, what concept allows a new class to derive properties and behaviors from an existing class? — Inheritance

20. Which OOP concept focuses on showing only essential features and hiding unnecessary details? — Abstraction

21. Consider a `Car` class inheriting from a `Vehicle` class. The `startEngine()` method is defined in `Vehicle` and overridden in `Car`. This is an example of: — Runtime Polymorphism

22. Which of the following is NOT a core principle of OOP? — Proceduralism

23. Which OOP concept is most related to the idea of 'is-a' relationship? — Inheritance

24. An abstract method is a method that: — Is declared but not implemented in the abstract class.

25. Polymorphism allows you to treat objects of different classes in a uniform way if they share a common: — Base class or interface

26. Which OOP principle involves bundling data (attributes) and methods (functions) that operate on the data within a single unit? —

27. What is the term for the mechanism that restricts direct access to some of an object's components, often referred to as 'data hiding'? — Encapsulation

28. What OOP principle allows objects of different classes to respond to the same method call in their own specific ways? — Polymorphism

29. The ability of a function or method to perform different actions based on the object it is acting upon is called: — Polymorphism

30. Which OOP principle helps in reducing complexity by modeling real-world entities? — Abstraction

31. Which OOP principle allows a single interface to represent multiple underlying forms? — Polymorphism

32. What does it mean for a class to be 'instantiable'? — Objects can be created from it.

33. What is a key advantage of polymorphism? — It simplifies the process of writing code for diverse object types.

34. In OOP, what are the characteristics or properties of an object called? — Attributes

35. The concept of 'object-oriented programming' was first popularized by which company? — Xerox

36. Consider a `Dog` class and a `Cat` class, both inheriting from an `Animal` class. This is an example of: — Hierarchical Inheritance

37. If a class `A` inherits from class `B`, and class `B` inherits from class `C`, this is an example of: — Multilevel Inheritance

38. In Object-Oriented Programming (OOP), what is a blueprint or a template for creating objects called? — Class

39. An abstract class can contain: — Both abstract and concrete methods.

40. Encapsulation helps in making code more: — Maintainable and secure

41. A method signature includes the method name and its: — Parameters

42. If a class has multiple methods with the same name but different parameter lists, this is an example of: — Compile-time Polymorphism

43. Which type of polymorphism allows a method to have the same name but different parameters in the same class? — Compile-time Polymorphism (Overloading)

44. What keyword is typically used to define an abstract class in many OOP languages? — abstract

45. If a class `Shape` has a method `draw()`, and `Circle`, `Square`, `Triangle` classes inherit from `Shape` and override `draw()`, calling `draw()` on a `Shape` reference pointing to a `Circle` object will execute: — The `draw()` method in the `Circle` class.

46. What does the term 'object state' refer to in OOP? — The values of the object's attributes at a particular point in time.

47. What is the main purpose of using abstract classes? — To enforce a common interface and structure for derived classes.

48. What is the primary goal of abstraction in software design? — To provide a high-level view while hiding implementation details.

49. What is the primary purpose of data hiding in encapsulation? — To protect the internal state of an object from unintended external modifications.

50. What is a common way to achieve abstraction in OOP? — Using abstract classes and interfaces.

Object Oriented Programming - class, object, encapsulation, inheritance, polymorphism, abstract classes - One Line Questions