20 Polymorphism Interview Questions and Answers

Polymorphism is a programming concept that allows developers to write code that is more flexible and adaptable. This concept can be difficult to understand and properly explain during a job interview. However, being able to effectively communicate your understanding of polymorphism can make you stand out from other candidates. In this article, we will review some common questions about polymorphism and how you can answer them.

Polymorphism Interview Questions and Answers

Here are 20 commonly asked Polymorphism interview questions and answers to prepare you for your interview:

1. What is polymorphism?

Polymorphism is the ability of an object to take on many different forms. In programming, this means that a single object can be used to represent different data types. For example, a single object could be used to represent an integer, a floating-point number, or a string.

2. Can you give me a simple example of how polymorphism works?

Polymorphism is the ability of an object to take on many different forms. A simple example of this is a person. A person can be a son, a daughter, a brother, a sister, an uncle, an aunt, etc. But at the end of the day, they are still just a person. In programming, an object can be given different forms by using inheritance.

3. How does the concept of polymorphism apply to object-oriented programming languages?

Polymorphism is the ability of an object to take on multiple forms. In object-oriented programming languages, this means that a single object can be used to represent multiple different types of objects. This can be useful for creating code that is more flexible and easier to reuse.

4. Is it possible for multiple classes to implement an interface in Java? If yes, then what are the benefits of doing so?

Yes, it is possible for multiple classes to implement an interface in Java. The benefits of doing so include increased code reuse and flexibility, as well as the ability to more easily change the implementation of the interface as needed.

5. What happens if two methods have different return types but share the same name and signature?

In this case, the method with the more specific return type will be chosen. For example, if one method returns an int and the other returns a double, the method returning the double will be chosen.

6. What’s your understanding of late binding in context with polymorphism?

Late binding is the process of dynamically linking together objects and methods at runtime, as opposed to early binding which happens at compile time. Late binding is often used in conjunction with polymorphism, which is the ability of an object to take on different forms depending on the context. Together, these two concepts allow for great flexibility in code, as the same object can be used in different ways depending on the situation.

7. Can you explain the difference between early binding and late binding? Which one provides better performance?

Early binding is when the compiler knows exactly which method to call at compile time, while late binding is when the compiler only knows the general type of object that it will be dealing with. Early binding is generally faster because the compiler can optimize the code better, but late binding can be more flexible.

8. Can you explain what type erasure is?

Type erasure is the process of removing all type information from a piece of code at compile time. This can be useful for making code more flexible and generic, but it can also lead to problems if the type information is needed at runtime.

9. What do you understand about virtual functions?

A virtual function is a member function of a base class that is declared using the virtual keyword. When a virtual function is called, the compiler will automatically choose the correct function to call based on the type of the object that is calling the function. This allows for polymorphism, or the ability to treat objects of different types in the same way.

10. Why can’t a class be both abstract and final at the same time?

A class cannot be both abstract and final at the same time because it would defeat the purpose of polymorphism. An abstract class is one that is meant to be extended by other classes, so that they can inherit its methods and add their own implementation. A final class, on the other hand, is one that cannot be extended. Therefore, if a class were both abstract and final, it would be impossible to inherit its methods and add your own implementation, which is the whole point of polymorphism.

11. Can you give me some examples of when runtime polymorphism may not work as expected?

One example of when runtime polymorphism may not work as expected is when you are trying to override a method that is declared as final in the parent class. Another example is when you are trying to override a method that is not declared as virtual in the parent class.

12. Can you explain what method overriding is?

Method overriding is a feature of object-oriented programming that allows a child class to provide a different implementation of a method that is already defined in the parent class. This can be useful if the child class wants to change the behavior of the method or if the child class wants to add additional functionality to the method.

13. What are the differences between overloading and overriding?

Overloading occurs when two or more methods in the same class have the same name but different signatures. Overriding occurs when a child class redefines a method from the parent class.

14. What do you understand about casting in context with OOPs concepts like inheritance, polymorphism, etc.?

Casting is the process of converting an object of one type into another. In the context of inheritance and polymorphism, casting can be used to convert a child object into a parent object, or vice versa. This can be useful when you need to access functionality that is only available in the parent object, or when you want to make sure that an object is treated as a specific type for the purposes of polymorphism.

15. What do you think would happen if we try to convert a subclass object into superclass’ reference variable?

It is not possible to convert a subclass object into a superclass reference variable.

16. In case of exception handling, which exceptions will take precedence – checked or unchecked?

Unchecked exceptions will always take precedence over checked exceptions. This is because unchecked exceptions are not checked by the compiler, and as such can occur anywhere in the code. Checked exceptions, on the other hand, are checked by the compiler and must be handled.

17. What’s the best way to achieve dynamic polymorphism in python?

The best way to achieve dynamic polymorphism in python is to use the __getattr__ method. This method allows you to intercept calls to undefined methods and attributes, and provides you with a way to dynamically respond to them. This is how many python libraries achieve dynamic polymorphism.

18. What’s your opinion on duck typing in Python? Will it interfere with polymorphism?

I think that duck typing is a great feature of Python that allows for a lot of flexibility in the language. I don’t think it necessarily interferes with polymorphism, but it does mean that you need to be careful when using duck typing to make sure that your code will still work as expected.

19. Can you discuss the pros and cons of using interfaces versus abstract classes?

There are a few key differences between interfaces and abstract classes that can help guide your decision on which to use. Abstract classes can contain implementation details for their methods, while interfaces can only contain method signatures. This means that if you need to provide any kind of functionality in your methods, you will need to use an abstract class.

Interfaces, on the other hand, are more flexible in that a class can implement multiple interfaces, while it can only extend one abstract class. This can be helpful if you need to provide different functionality depending on the context. However, interfaces can be more difficult to work with since you don’t have any implementation details to work with.

20. What are similarities between C++ templates and generics?

Both C++ templates and generics provide a way to create type-safe code that can be used with multiple types. Templates are compiled when the code is compiled, while generics are compiled when the code is run. This means that templates can be more efficient, but generics are more flexible.