Real Time Interview Q&A

Top 30+ OOPS Real Time Interview Questions

Top 30+ OOPS Real Time Interview Questions

 

OOP languages are embedded languages that support OOP principles such as encapsulation, inheritance, polymorphism, and abstraction. Now let’s take a look at the following example OOP languages:

Popular OOP Languages:

Top 30+ OOPS Real Time Interview Questions

 

Here’s a tabular comparison of popular OOP languages based on key features:

Language Fully OOP? Primary Use Case Multi-Paradigm Support Memory Management Platform Notable Features
C++ No (Hybrid) System Programming, Game Dev Yes (OOP + Procedural) Manual (with smart pointers) Cross-platform Fast performance, multiple inheritance
Java Yes Enterprise, Web, Android Yes (OOP + Functional) Automatic (Garbage Collection) Cross-platform (JVM) Strong type safety, rich libraries
Python Yes Web, AI, Scripting Yes (OOP + Functional + Procedural) Automatic (Garbage Collection) Cross-platform Dynamic typing, simplicity
C# Yes .NET, Game Dev (Unity) Yes (OOP + Functional) Automatic (Garbage Collection) Windows, Cross-platform (via .NET) Strong integration with Microsoft ecosystem
JavaScript No (Prototype-based OOP) Web Dev, Backend (Node.js) Yes (Functional + OOP) Automatic Cross-platform (Browser, Node.js) Prototype inheritance, event-driven
Swift Yes iOS/macOS Apps Yes (OOP + Functional) Automatic (ARC) Apple Ecosystem Type safety, modern syntax
Kotlin Yes Android, Backend Yes (OOP + Functional) Automatic (GC) Cross-platform (JVM, Native) Concise, null safety
Ruby Yes Web Dev (Rails) Yes (OOP + Metaprogramming) Automatic (GC) Cross-platform Everything is an object
PHP No (Hybrid) Web Dev (Backend) Yes (Procedural + OOP) Automatic (GC) Web Servers Easy to learn, wide adoption
Objective-C Yes iOS/macOS (Legacy) Yes (OOP + Procedural) Automatic (ARC) Apple Ecosystem Message-passing, influenced by Smalltalk

 

 

Top 30+ OOPS Real Time Interview Questions
Top 30+ OOPS Real Time Interview Questions

Top 30+ OOPS Real Time Interview Questions

  1. 4 Pillars of OOPS?
  2. What are Class and object?
  3. What is Abstraction?
  4. What is Encapsulation?
  5. What is Inheritance?
  6. Types of Inheritance?
  7. Diamond Problem?
  8. What is Polymorphism and its types?
  9. What is Compile-time polymorphism?
  10.  What are Function Overloading and Operator Overloading?
  11.  What is New Operator and Delete Operator?
  12. What is Run Time Polymorphism?
  13.  What are VTable and VPtr?
  14.  What is a Constructor?
  15.  Types of Constructors?
  16.  Write your own copy constructor and own assignment operator.
  17.  What is Move Constructor?
  18.  Write your own move constructor and own move assignment operator
  19.  What are Destructors?
  20.  What is a Virtual Destructor?
  21.  What are Const Variables and How do initialize in constructors?
  22.  What are Static Variables and Static Methods?
  23.  What is Friend Functions?
  24.  What are Smart Pointers?
  25.  What are weak Pointers, and shared Pointers?
  26.  Types Of Casting?
  27.  What are Dynamic Casting and Static Casting?
  28.  What is Object Slicing?
  29.  What is the use of an Explicit Keyword?
  30.  What is a Function Pointer?
  31.  2D array Initiation?
  32.  Write Your Own Vector?
  33.  What are lambda functions?

Here’s a tabular format covering all your OOPs concepts in a structured manner:

Top 30+ OOPS Real Time Interview Questions

for JAVA ,C++,PYTHON etc

Concept Explanation
4 Pillars of OOP Encapsulation, Abstraction, Inheritance, Polymorphism
Abstraction Hiding implementation details and showing only the necessary features to the user (e.g., using abstract classes and interfaces).
Encapsulation Wrapping data and functions into a single unit (class) and restricting direct access using access modifiers (private, protected, public).
Inheritance Mechanism where a class (child) derives properties and behaviors from another class (parent). Promotes code reusability.
Types of Inheritance Single (one parent → one child) – Multiple (one child inherits multiple parents) – Multilevel (grandparent → parent → child) – Hierarchical (one parent → multiple children) – Hybrid (combination of multiple inheritance types)
Diamond Problem Occurs in multiple inheritance when a child class inherits from two classes that share a common base class, causing ambiguity. Solved using virtual inheritance in C++.
Polymorphism Ability of an entity (method or operator) to take multiple forms. Two types: Compile-time (early binding) and Run-time (late binding).
Compile-time Polymorphism Achieved using function overloading and operator overloading where function calls are resolved at compile-time.
Function Overloading Defining multiple functions with the same name but different parameters (different number or type of arguments).
Operator Overloading Redefining operators (+, -, *, =, etc.) to work with user-defined types (classes).
New and Delete Operators new dynamically allocates memory for objects, delete deallocates it. Example: int* p = new int(5); delete p;
Run-time Polymorphism Achieved through method overriding and virtual functions, resolved at runtime using dynamic binding (vtable mechanism).
VTable & VPtr VTable (Virtual Table): Table storing addresses of virtual functions. – VPtr (Virtual Pointer): Pointer to VTable, maintained per object to resolve function calls dynamically.
Constructor Special function executed when an object is created. Used for initialization.
Types of Constructors Default (no arguments) – Parameterized (with arguments) – Copy (creates a new object as a copy of an existing object) – Move (optimizes resource transfer in temporary objects)
Copy Constructor ClassName(const ClassName &obj) { /* copy logic */ }
Assignment Operator (Overloaded) ClassName& operator=(const ClassName &obj) { /* assignment logic */ return *this; }
Move Constructor ClassName(ClassName&& obj) { /* move logic */ }
Move Assignment Operator ClassName& operator=(ClassName&& obj) { /* move assignment logic */ return *this; }
Destructors Special function (~ClassName()) called when an object goes out of scope to free resources.
Virtual Destructor Ensures derived class destructor is called first in polymorphic scenarios. virtual ~ClassName() {}
Const Variables in Constructor Initialized using an initializer list: ClassName() : myConstVar(10) {}
Static Variables & Methods Static Variables: Shared among all instances of a class. – Static Methods: Can be called without an object (ClassName::method()).
Friend Functions Non-member function that can access private/protected members of a class (friend keyword).
Smart Pointers unique_ptr, shared_ptr, and weak_ptr manage memory automatically.
Weak & Shared Pointers Shared Pointer (shared_ptr): Reference-counted ownership. – Weak Pointer (weak_ptr): Non-owning reference to prevent cyclic dependencies.
Types of Casting static_cast (compile-time type conversion) – dynamic_cast (safe downcasting) – const_cast (removes const qualifier) – reinterpret_cast (converts pointer types)
Dynamic vs Static Casting Static Casting (static_cast): Compile-time conversion. – Dynamic Casting (dynamic_cast): Used for polymorphism, checks type safety at runtime.
Object Slicing When a derived class object is assigned to a base class object, the extra properties of the derived class are sliced off.
Explicit Keyword Prevents implicit conversions when using single-parameter constructors. explicit ClassName(int x);
Function Pointer A pointer that stores the address of a function. Example: void (*ptr)() = &func;
2D Array Initialization int arr[3][3] = {{1,2,3}, {4,5,6}, {7,8,9}};
Write Your Own Vector Implement dynamic array with push_back, pop_back, resize, etc.
Lambda Functions Anonymous functions used for short, inline operations. Syntax: [capture](parameters) { body }

Top 30+ OOPS Real Time Interview Questions

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