What are design patterns, how do they relate to OOP, and can you explain the Singleton, Factory, and Observer patterns?

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OOP Interview Questions

  1. [JUNIOR] What is Object-Oriented Programming and why is it important?
  2. [JUNIOR] What are the four main principles of OOP?
  3. [JUNIOR] What is a class and what is an object?
  4. [JUNIOR] What is encapsulation and why is it useful?
  5. [JUNIOR] What is inheritance and what is its purpose?
  6. [JUNIOR] What is polymorphism and what are its types?
  7. [MID] What is the difference between an abstract class and an interface, and when would you use each?
  8. [MID] What is the difference between composition and inheritance, and when would you choose one over the other?
  9. [SENIOR] How do you apply the Single Responsibility Principle in practice, and what are signs that a class violates it?
  10. [JUNIOR] What is abstraction and how is it achieved in OOP?
  11. [JUNIOR] What are access modifiers and what is their significance?
  12. [JUNIOR] What is the difference between method overloading and method overriding?
  13. [MID] What are the SOLID principles and why are they important?
  14. [MID] What is the difference between compile-time (static) polymorphism and runtime (dynamic) polymorphism?
  15. [MID] What are the different types of inheritance and what are the potential problems with multiple inheritance?
  16. [SENIOR] How does the Open-Closed Principle guide extensible design without modifying existing code?
  17. [SENIOR] What is the Liskov Substitution Principle and how can violating it lead to subtle bugs?
  18. [JUNIOR] What is a constructor and what are the different types of constructors?
  19. [JUNIOR] What is a destructor and when is it called?
  20. [MID] What is a copy constructor and when is it needed?
  21. [MID] What are virtual functions and pure virtual functions?
  22. [MID] What is the difference between shallow copy and deep copy of objects?
  23. [MID] What is method resolution order (MRO) and how does it handle the diamond problem in multiple inheritance?
  24. [SENIOR] How do you decide between using inheritance hierarchies and composition with dependency injection in a large codebase?
  25. [SENIOR] What is the Interface Segregation Principle and how does it prevent interface pollution?
  26. [SENIOR] What is the Dependency Inversion Principle and how does it relate to dependency injection?
  27. [SENIOR] How do you design class hierarchies that are resilient to changing requirements?
  28. [JUNIOR] What is the difference between a class and a structure?
  29. [JUNIOR] What are the advantages and disadvantages of OOP compared to procedural programming?
  30. [MID] What is the difference between association, aggregation, and composition relationships?
  31. [MID] What is operator overloading and what are its limitations?
  32. [MID] What is garbage collection and how does it work in OOP languages?
  33. [MID] What is exception handling in OOP and how does the try-catch-finally mechanism work?
  34. [SENIOR] What are design patterns, how do they relate to OOP, and can you explain the Singleton, Factory, and Observer patterns?
  35. [SENIOR] What is the Template Method pattern and how does it leverage inheritance and polymorphism?
  36. [SENIOR] How does the Strategy pattern use polymorphism to achieve interchangeable algorithms?
  37. [SENIOR] What is the difference between cohesion and coupling, and how do they affect class design?
  38. [EXPERT] How do object layout, vtable dispatch, and memory alignment affect runtime performance in polymorphic code?
  39. [JUNIOR] What is the difference between procedural programming and object-oriented programming?
  40. [JUNIOR] How much memory does a class occupy versus an object?
  41. [MID] What is constructor chaining and how is it implemented?
  42. [MID] What is the difference between early binding and late binding?
  43. [MID] What are friend functions and friend classes, and when should they be used?
  44. [SENIOR] How do you balance the use of OOP features like inheritance with performance considerations in latency-sensitive systems?
  45. [SENIOR] How do you handle cross-cutting concerns like logging and caching in an OOP system without violating SOLID principles?
  46. [SENIOR] What is the Decorator pattern and how does it provide a flexible alternative to subclassing?
  47. [EXPERT] How does the expression problem manifest in OOP and what design techniques address it?
  48. [EXPERT] How do you design an object model that supports both serialization and versioning without breaking encapsulation?
  49. [EXPERT] What are the trade-offs between classical OOP inheritance and algebraic data types with pattern matching found in functional languages?
  50. [JUNIOR] What are some commonly used object-oriented programming languages?
  51. [MID] What is the difference between a concrete class, an abstract class, and an interface in a class hierarchy?
  52. [MID] What is a sealed or final class and why would you use one?
  53. [SENIOR] How does the concept of invariants relate to class design and encapsulation?
  54. [SENIOR] What are mixins and traits, and how do they offer an alternative to multiple inheritance?
  55. [EXPERT] How does metaprogramming and reflection interact with OOP principles, and what are the risks?
  56. [EXPERT] What is the Visitor pattern, how does it use double dispatch, and what are its limitations?
  57. [EXPERT] How do you design domain models that enforce business invariants at the type level using OOP constructs?
  58. [JUNIOR] What programming paradigms exist besides OOP?
  59. [SENIOR] How do you refactor a large class with too many responsibilities into smaller, well-designed classes?
  60. [EXPERT] How does the Curiously Recurring Template Pattern (CRTP) achieve static polymorphism and when is it preferable to virtual dispatch?
  61. [EXPERT] What are phantom types and how can they be used in OOP languages to enforce compile-time constraints?
  62. [EXPERT] How do different memory models and garbage collection strategies affect the design of concurrent object-oriented systems?