Top 30 Most Common oops question for interview You Should Prepare For

Landing a job in software development often hinges on how well you understand and can articulate Object-Oriented Programming (OOP) concepts. Preparing for oops question for interview is crucial. Mastering commonly asked questions boosts confidence, clarity, and overall interview performance. This guide presents the top 30 oops question for interview you're likely to encounter, along with detailed strategies to ace them.

What are oops question for interview?

Oops question for interview are designed to assess your knowledge and practical understanding of object-oriented programming principles. These questions delve into the core concepts of OOP, such as encapsulation, inheritance, polymorphism, and abstraction. Interviewers use these questions to evaluate your ability to apply these principles in real-world scenarios. Successfully answering oops question for interview demonstrates your competency in designing and developing robust, maintainable, and scalable software. They often explore your understanding of classes, objects, and their relationships, as well as your ability to differentiate between various OOP concepts.

Why do interviewers ask oops question for interview?

Interviewers ask oops question for interview to gauge your ability to think in an object-oriented manner and to assess your problem-solving skills. They want to determine if you can effectively use OOP principles to design and implement software solutions. These questions help interviewers evaluate your practical experience and ability to apply theoretical knowledge. By asking oops question for interview, they can assess your grasp of fundamental concepts and your ability to explain them clearly and concisely. Moreover, understanding of oops question for interview indicates your potential for growth and contribution to the team.

Here's a quick preview of the 30 oops question for interview we'll cover:

• 1. What does OOPS stand for?

• 2. What are the four basic concepts of OOPS?

• 3. What is a class?

• 4. What is an object?

• 5. What is encapsulation?

• 6. What is abstraction?

• 7. What is inheritance?

• 8. What is polymorphism?

• 9. What is the difference between a class and an object?

• 10. What is a constructor?

• 11. What is the difference between method overloading and method overriding?

• 12. What is type casting?

• 13. What is an interface?

• 14. Why should you program to an interface?

• 15. What is an abstract class?

• 16. What is the difference between an abstract class and an interface?

• 17. What is multiple inheritance?

• 18. What are the subcategories of inheritance?

• 19. What is encapsulation, and give an example?

• 20. Explain the concept of inheritance with an example.

• 21. What is a static constructor?

• 22. What is cohesion?

• 23. What is coupling?

• 24. Differentiate between cohesion and coupling.

• 25. What is a destructor?

• 26. What is method overriding?

• 27. What is a friend function?

• 28. What is a virtual function?

• 29. What is abstraction in programming?

• 30. How does inheritance differ from composition?

## 1. What does OOPS stand for?

Why you might get asked this:

This is a foundational question to ensure you understand the basic terminology. It assesses whether you're familiar with the core concept underpinning object-oriented programming. Successfully answering this shows you know the very basics of what oops question for interview are testing.

How to answer:

Simply state the full form of OOPS. There's no need to overcomplicate it. Ensure you pronounce each word clearly.

Example answer:

"OOPS stands for Object-Oriented Programming System. It's a paradigm focused on organizing software design around objects."

## 2. What are the four basic concepts of OOPS?

Why you might get asked this:

This tests your understanding of the core principles that define OOP. Interviewers want to know if you grasp the fundamental building blocks of object-oriented design and development. A solid understanding of these concepts is crucial for dealing with oops question for interview.

How to answer:

List the four concepts: encapsulation, abstraction, inheritance, and polymorphism. Briefly explain each.

Example answer:

"The four basic concepts of OOPS are encapsulation, abstraction, inheritance, and polymorphism. Encapsulation bundles data and methods, abstraction hides complexity, inheritance allows classes to inherit properties, and polymorphism enables objects to take on many forms."

## 3. What is a class?

Why you might get asked this:

This question assesses your understanding of the fundamental structure in OOP. Knowing what a class is is crucial before you can tackle more complex oops question for interview.

How to answer:

Explain that a class is a blueprint or template for creating objects. It defines the properties and behaviors of those objects.

Example answer:

"A class is a blueprint for creating objects. Think of it like a cookie cutter; it defines the shape and characteristics of the cookies (objects) you'll create."

## 4. What is an object?

Why you might get asked this:

Understanding the difference between a class and an object is fundamental. This question directly checks your grasp of this distinction. Many oops question for interview build upon this core understanding.

How to answer:

Explain that an object is an instance of a class. It has its own set of data and can perform the actions defined in the class.

Example answer:

"An object is a specific instance of a class. So, if 'Car' is the class, a specific red Toyota Camry would be an object of that class, with its own unique characteristics."

## 5. What is encapsulation?

Why you might get asked this:

Encapsulation is a key principle for data protection and code organization. This question tests your understanding of its purpose and benefits. This is important as many oops question for interview revolve around concepts of good design.

How to answer:

Explain that encapsulation is bundling data and methods that operate on that data within a single unit (a class). It protects the data from outside access and misuse.

Example answer:

"Encapsulation is like a capsule that bundles data and the methods that operate on it. It protects the data from being directly accessed or modified from outside the class, ensuring data integrity."

## 6. What is abstraction?

Why you might get asked this:

Abstraction simplifies complex systems by hiding unnecessary details. This question assesses your understanding of this important concept. Abstraction is a concept touched on often in oops question for interview.

How to answer:

Explain that abstraction is showing only the essential information to the user while hiding the internal complexity.

Example answer:

"Abstraction is showing only what's necessary and hiding the complex details. Think of driving a car; you only need to know how to use the steering wheel, gas pedal, and brakes, not the inner workings of the engine."

## 7. What is inheritance?

Why you might get asked this:

Inheritance promotes code reusability and establishes relationships between classes. This question checks your understanding of this core concept. Interviewers are trying to ascertain if you can discuss and apply these concepts, so preparation for oops question for interview is key.

How to answer:

Explain that inheritance allows a class (child class) to inherit properties and behaviors from another class (parent class).

Example answer:

"Inheritance is when one class inherits properties and methods from another class. For instance, a 'SportsCar' class could inherit from a 'Car' class, automatically gaining properties like 'number of wheels' and 'engine type'."

## 8. What is polymorphism?

Why you might get asked this:

Polymorphism adds flexibility and adaptability to your code. This question assesses your understanding of its different forms and benefits. The idea of polymorphism is discussed regularly in oops question for interview.

How to answer:

Explain that polymorphism is the ability of an object to take on many forms. Discuss method overloading and method overriding as examples.

Example answer:

"Polymorphism means 'many forms.' It allows objects to be treated as instances of their parent class. For example, a 'draw' method could behave differently for a 'Circle' object versus a 'Square' object."

## 9. What is the difference between a class and an object?

Why you might get asked this:

This tests your understanding of the relationship between a blueprint and its instance. It's a fundamental distinction in OOP. This is tested regularly in oops question for interview.

How to answer:

Explain that a class is a template or blueprint, while an object is a specific instance created from that template.

Example answer:

"A class is like a blueprint for a house, defining the structure and features. An object is the actual house built from that blueprint. You can build many houses (objects) from the same blueprint (class)."

## 10. What is a constructor?

Why you might get asked this:

Constructors are crucial for object initialization. This question ensures you understand their purpose and how they work. Expect this in oops question for interview.

How to answer:

Explain that a constructor is a special method used to initialize objects when they are created. It sets the initial values of the object's attributes.

Example answer:

"A constructor is a special method that's automatically called when an object is created. It's used to set up the object's initial state, like giving a 'Person' object a default name and age."

## 11. What is the difference between method overloading and method overriding?

Why you might get asked this:

This distinguishes two different ways to achieve polymorphism. It's important to understand the nuances of each. This is a common request in oops question for interview.

How to answer:

Explain that method overloading involves multiple methods with the same name but different parameters in the same class. Method overriding involves a child class providing a specific implementation for a method already defined in its parent class.

Example answer:

"Method overloading is having multiple methods in the same class with the same name but different parameters. Method overriding is when a subclass provides a specific implementation for a method that’s already defined in its parent class."

## 12. What is type casting?

Why you might get asked this:

Type casting allows you to treat an object as a different type. This question checks your understanding of its purpose and potential risks. This can arise in discussion in oops question for interview.

How to answer:

Explain that type casting is converting an object of one type into another type. Discuss the difference between implicit and explicit casting.

Example answer:

"Type casting is converting an object from one data type to another. For example, you might cast a floating-point number to an integer, or cast a generic object to a more specific type of object."

## 13. What is an interface?

Why you might get asked this:

Interfaces define a contract that classes can implement. This question assesses your understanding of their purpose and benefits. This is important to understand for approaching oops question for interview.

How to answer:

Explain that an interface is a contract that defines a set of methods that a class must implement.

Example answer:

"An interface defines a set of methods that a class must implement. It’s like a contract; any class that implements the interface promises to provide implementations for all the methods defined in that interface."

## 14. Why should you program to an interface?

Why you might get asked this:

Programming to an interface promotes flexibility and loose coupling. This question checks your understanding of good design principles. The reasoning for this is often discussed in oops question for interview.

How to answer:

Explain that programming to an interface provides flexibility, reduces coupling, and makes code more maintainable and testable.

Example answer:

"Programming to an interface allows for more flexible and loosely coupled code. If you depend on the interface instead of concrete classes, you can easily swap out different implementations without affecting the rest of your code."

## 15. What is an abstract class?

Why you might get asked this:

Abstract classes provide a base for creating more specific classes. This question assesses your understanding of their purpose and how they differ from interfaces. This is important when understanding the context of oops question for interview.

How to answer:

Explain that an abstract class is a class that cannot be instantiated and is designed to be inherited by other classes. It may contain both abstract and concrete methods.

Example answer:

"An abstract class is a class that cannot be instantiated directly. It's designed to be a base class for other classes, providing a common interface and some shared implementation. It can contain both abstract methods (which must be implemented by subclasses) and concrete methods (which provide default behavior)."

## 16. What is the difference between an abstract class and an interface?

Why you might get asked this:

This distinguishes two similar concepts with important differences. It's a common question to test your depth of understanding. You should expect this in oops question for interview.

How to answer:

Explain that an abstract class can have both abstract and concrete methods and state variables, while an interface can only have abstract methods (or default methods in some languages) and constants. Also, a class can inherit from only one abstract class but can implement multiple interfaces.

Example answer:

"The key difference is that a class can inherit from only one abstract class but can implement multiple interfaces. Abstract classes can have both abstract and concrete methods, while interfaces typically only define abstract methods."

## 17. What is multiple inheritance?

Why you might get asked this:

Multiple inheritance allows a class to inherit from multiple parent classes. This question assesses your awareness of this feature and its potential complexities. Knowing what to avoid is important as part of oops question for interview.

How to answer:

Explain that multiple inheritance allows a class to inherit from more than one parent class. Mention potential issues like the diamond problem.

Example answer:

"Multiple inheritance is when a class inherits from more than one parent class. While it can be powerful, it can also lead to complexities like the diamond problem, where conflicts arise if the parent classes have methods with the same name."

## 18. What are the subcategories of inheritance?

Why you might get asked this:

This tests your understanding of the different inheritance models and their characteristics. Interviewers expect you to know some of these when answering oops question for interview.

How to answer:

List and briefly explain the subcategories: single, multiple, multilevel, and hierarchical inheritance.

Example answer:

"The subcategories of inheritance include single inheritance (one child from one parent), multiple inheritance (one child from multiple parents), multilevel inheritance (inheritance through multiple levels of parent-child relationships), and hierarchical inheritance (multiple children from a single parent)."

## 19. What is encapsulation, and give an example?

Why you might get asked this:

This combines the definition of encapsulation with a practical example to ensure you understand its real-world application. Practicing examples will help when answering oops question for interview.

How to answer:

Explain that encapsulation is hiding data and exposing methods to access it. Provide an example like a bank account where the balance is hidden but can be accessed through methods like deposit and withdrawal.

Example answer:

"Encapsulation is bundling data and methods together and hiding the internal state of an object. A good example is a bank account: the actual account balance is private and can only be accessed and modified through methods like deposit and withdraw, preventing direct manipulation."

## 20. Explain the concept of inheritance with an example.

Why you might get asked this:

This tests your ability to explain inheritance in a clear and practical way. Explaining concepts clearly is something interviewers look for when posing oops question for interview.

How to answer:

Explain that inheritance is when one class inherits properties from another. Provide an example like a Car class inheriting from a Vehicle class.

Example answer:

"Inheritance is when one class inherits properties and behaviors from another class. For example, we might have a base class called 'Animal' with properties like 'name' and 'age', and methods like 'eat' and 'sleep'. Then, we could have a 'Dog' class that inherits from 'Animal', automatically getting those properties and methods, but also adding its own specific properties like 'breed' and methods like 'bark'."

## 21. What is a static constructor?

Why you might get asked this:

Static constructors are used to initialize static data. This question assesses your understanding of their purpose and behavior. This is more advanced than some oops question for interview.

How to answer:

Explain that a static constructor is a special constructor that initializes static data. It runs before any instance of the class is created.

Example answer:

"A static constructor is a special constructor that's used to initialize static members of a class. It's called automatically only once, before the first instance of the class is created or any static members are referenced."

## 22. What is cohesion?

Why you might get asked this:

Cohesion refers to how well the elements inside a module belong together. High cohesion is desirable in good design. Knowing the purpose is an important part of oops question for interview.

How to answer:

Explain that cohesion refers to the degree to which the elements inside a module are related to each other. High cohesion means the elements are highly related and focused on a single task.

Example answer:

"Cohesion refers to the degree to which the elements inside a module or class are related to each other. High cohesion means that the elements within the module are focused on a single, well-defined purpose, making the module easier to understand and maintain."

## 23. What is coupling?

Why you might get asked this:

Coupling refers to how much one module depends on others. Low coupling is preferable for maintainability and flexibility. This is part of a wider design discussion, such as what is raised in oops question for interview.

How to answer:

Explain that coupling refers to the degree to which one module depends on other modules. Low coupling means the modules are relatively independent, making the system easier to change and maintain.

Example answer:

"Coupling refers to the degree to which one module depends on other modules. Low coupling is desirable because it means that changes in one module are less likely to affect other modules, making the system more maintainable and easier to test."

## 24. Differentiate between cohesion and coupling.

Why you might get asked this:

This tests your understanding of these two important design principles and their relationship to each other. It builds on questions like oops question for interview.

How to answer:

Explain that cohesion refers to how well elements within a module interact, while coupling refers to how much modules interact with each other. High cohesion and low coupling are generally desirable.

Example answer:

"Cohesion refers to how well the elements within a module are related and focused on a single purpose. Coupling refers to how much different modules depend on each other. We want high cohesion within modules and low coupling between modules."

## 25. What is a destructor?

Why you might get asked this:

Destructors are used to release resources when an object is destroyed. This question assesses your understanding of memory management. This is more relevant to some languages than others when faced with oops question for interview.

How to answer:

Explain that a destructor is a method that releases memory allocated by the class when an object is about to be destroyed.

Example answer:

"A destructor is a special method that's automatically called when an object is about to be destroyed. It's used to release any resources that the object was holding, like memory or file handles."

## 26. What is method overriding?

Why you might get asked this:

Method overriding allows a child class to provide a specific implementation for a method already defined in its parent class. This question ensures you understand its purpose and how it achieves polymorphism. Many oops question for interview will ask about polymorphism.

How to answer:

Explain that method overriding is when a child class provides a specific implementation for a method that is already defined in its parent class. The child class's method must have the same name, return type, and parameters as the parent class's method.

Example answer:

"Method overriding is when a subclass provides its own implementation of a method that's already defined in its superclass. This allows the subclass to customize the behavior of the inherited method while maintaining the same method signature."

## 27. What is a friend function?

Why you might get asked this:

Friend functions have access to the private and protected members of a class. This question assesses your understanding of this concept and its potential uses and drawbacks. This is more specific to certain languages when discussing oops question for interview.

How to answer:

Explain that a friend function is a non-member function that has access to the private and protected members of a class.

Example answer:

"A friend function is a function that's not a member of a class but has special access to the private and protected members of that class. It's declared using the 'friend' keyword inside the class definition."

## 28. What is a virtual function?

Why you might get asked this:

Virtual functions are crucial for achieving runtime polymorphism. This question assesses your understanding of their purpose and how they enable dynamic dispatch. This is particularly important in the context of oops question for interview.

How to answer:

Explain that a virtual function is a member function in a base class that can be overridden by a derived class. When a virtual function is called through a base class pointer or reference, the actual function that is executed is determined at runtime based on the object's actual type.

Example answer:

"A virtual function is a member function declared in a base class that can be redefined in a derived class. When you call a virtual function through a pointer or reference to the base class, the actual function that gets executed is determined at runtime based on the object's dynamic type."

## 29. What is abstraction in programming?

Why you might get asked this:

Abstraction is showing only essential features while hiding the internal details. This question assesses your understanding of its purpose and how it simplifies complex systems. This is something that interviewers want to see if you understand as part of answering oops question for interview.

How to answer:

Explain that abstraction is the concept of showing only essential features while hiding the internal details.

Example answer:

"Abstraction is the process of simplifying complex systems by modeling classes appropriate to the problem, and at the correct level of detail. Hiding the implementation details from the user, only the service is exposed."

## 30. How does inheritance differ from composition?

Why you might get asked this:

This distinguishes two different ways to establish relationships between classes. It's important to understand the trade-offs between them. Knowing when to apply this is key when dealing with oops question for interview.

How to answer:

Explain that inheritance creates an is-a relationship between classes (e.g., a car is a vehicle), while composition creates a has-a relationship (e.g., a car has an engine).

Example answer:

"Inheritance creates an 'is-a' relationship, where a subclass inherits properties and behaviors from a superclass. Composition creates a 'has-a' relationship, where a class contains instances of other classes as its members. Use inheritance when you want to create a specialized version of an existing class, and use composition when you want to combine the functionality of multiple classes."

Other tips to prepare for a oops question for interview

Practicing your responses out loud is extremely valuable. Mock interviews with friends or colleagues can provide useful feedback on your clarity and delivery. Review common design patterns and be prepared to discuss how they relate to OOP principles. Understanding design patterns will help contextualize your answers to oops question for interview. Create a study plan and allocate specific time slots for reviewing each OOP concept. Focus on understanding the underlying principles rather than just memorizing definitions. Consider using AI tools like Verve AI to practice answering questions in a simulated interview environment. Always relate your answers back to your own experiences. Providing specific examples from your projects demonstrates your practical understanding and solidifies your credibility.

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