Common OOP Interview Questions
Below are some commonly asked OOP interview questions and their explanations.These OOP interview questions are designed to test your understanding of core object-oriented programming concepts.Preparing for these OOP interview questions will help you stand out and showcase your skill during technical interviews.
What are the four pillars of OOP?
The four pillars of OOP are basic concepts that form the establishment of object-oriented programming. They are:
1.Encapsulation:
- Encapsulation means binding or wrapping the members of a class within its class body with the help of access specifiers. It limits direct access to a few of the object’s components and guarantees that information is accessed as it were through well-defined methods.
- This makes a difference to defend the object’s inside state from undesirable changes.
2.Abstraction:
- Abstraction includes hiding the complex execution details and exposing as it were the essential parts of an object.
- It permits developers to focus on what an object does, instead of how it does it.
- For example, when using a smartphone, clients connected with the interface without stressing around the complicated workings of the hardware.
3.Inheritance:
- One class acquiring the property of another class with the help of extends keyword.
- Super class is a one from which we acquired the properties.
- Sub class is a one to which properties are delivered.
- This component advances code reuse and builds up a common progression.
- For instance, a Dog class can acquire from a Animal class, permitting Dog to share common characteristics like eat or sleep without having to rethink them.
4.Polymorphism:
- Polymorphism permits objects to be treated as instances of their parent class whereas giving particular behavior for the child class.
- There are two types of polymorphism:
- Compile-time polymorphism (Method overloading)
- Run-time polymorphism (Method overriding)
2.What is the difference between method overloading and method overriding?
Method Overloading:
- Method Overloading refers to characterizing numerous methods inside the same class with the same name but different parameters (either in number or type).
- Typically a form of compile-time polymorphism.
- For instance, you’ll be able have add(int a, int b) and add(double a, double b) within the same class.
Method Overriding
- Method Overriding happens when a subclass gives a particular execution of a method that’s as of now characterized in its parent class.
- This is often a form of run-time polymorphism.
- The subclass method has the same signature as the parent class method and is invoked based on the real object type at runtime.
3.What is the difference between a class and an object?
- A class can be a blueprint or template, because by using a one class we can create multiple instance or object of the class.
- An object is an instance of a class. Once you make an object, you’re allocating memory and characterizing the state of that object based on the class.
- For example, consider a Car class. The class may have attributes like color, model, and speed, and methods like accelerate() and brake(). An object of this class may be car1, representing a particular car with values for these attributes.
4.What is a constructor and why is it important?
- A constructor is a special method in a class that’s subsequently invoked when an object is made.
- It is utilized to initialize the object’s state or set initial values for its attributes.
- Constructors are pivotal since they guarantee that an object is in a valid state as before long because it is made.
- For example, in case you make a Person class, you might utilize a constructor to set the person’s name and age when an object of that class is instantiated.
5.What is method overriding in polymorphism?
- Method overriding in polymorphism refers to the capacity of a subclass to provide a specific execution for a method that’s as of presently characterized in its superclass.
- When a method is overridden, the subclass’s version of the method is called, without a doubt in case the method is called on an object of the superclass type.
- This empowers runtime polymorphism and dynamic method dispatch.
- For example, in the event that both Dog and Cat acquire from an Animal class and override the sound() method, calling sound() on a Dog object will invoke the Dog version of the method, indeed in spite of the fact that the reference type is Animal.
6.What is the difference between static and instance vairables/methods?
- Static variables/methods belong to the class instead of any particular instance of the class. They are shared among all instances. For example, a count variable in a class seem track how numerous objects have been made.
- Instance variables/methods belong to particular objects made from the class. Each object has its own copy of these variables and methods.
7.What is inheritance and its benifits?
- Inheritance is the mechanism by which one class acquires properties from another. It permits for code reuse, reduces repetition, and builds up a hierarchy.
- The benefits include:
- Code Reusability: You’ll reuse existing code in subclasses.
- Extensibility: You’ll include new functionality to existing classes.
- Hierarchical Classification: It permits modeling of real-world relationships (e.g., an Employee class acquiring from a Person class).