50 OOPS Interview Questions asked in SRM Placements

21. What are the limitations of inheritance?

It Increases the execution time and effort. It also requires jumping back and forth between different classes. The parent class and the child class are always tightly coupled. Afford modifications in the program would require changes for the parent and the child's class. Inheritance requires careful implementation otherwise it would lead to incorrect results.

22. What is a superclass?

A superclass is a class from which a subclass or child class is derived. Base class and parent class are other names for a superclass. For example, if Student is a class derived from the Person class, then the Person class will be referred to as the superclass.

A superclass or base class is also a class that works as a parent to some other class/ classes.

For example, the Vehicle class is a superclass of class Bike.

23. What is a subclass?

A class that derives from another class is referred to as a subclass. A subclass inherits the properties of its ancestors or parent classes. For example, the class Bike is a subclass or a derivative of the Vehicle class.

24. What is Polymorphism?

Polymorphism is one of the most used and core concepts in OOP languages. It explains the concept of different classes can be used with the same interface. Each of these classes can have its own implementation of the interface. 

25. What is static polymorphism?

In OOP, static polymorphism determines which method to call at compile time. For the same trigger with static polymorphism, the object might respond differently. Function, constructor and operator overloading are examples of static polymorphism.

26. What is dynamic polymorphism?

Dynamic polymorphism is a method or process that handles a call to an overridden method during runtime rather than at compile time. It is also referred to as dynamic method dispatch or runtime polymorphism. Using method overriding, we can create dynamic polymorphism. An example of runtime polymorphism: is method overriding.

27. What is operator overloading?

The user-defined data type is given a special meaning by the operator using operator overloading. It is a compile-time polymorphism.

28. Differentiate between overloading and overriding.

When two or more methods in the same class have the same name but different parameters, this is referred to as overloading. The technique of using the same method signature, i.e., name and parameters, in both the superclass and the child class is known as overriding.

29. What is encapsulation?

Encapsulation is used to wrap the data and the code which works in a single unit together. Example: Encapsulation allows data-hiding as the data specified in one class is hidden from other classes.

30. What is the difference between public, private and protected access modifiers?

In object-oriented programming languages, access modifiers are used to specify the visibility and accessibility of class members (fields, methods, and constructors). There are three types of access modifiers:

1. Public: Members marked as public can be accessed from anywhere within the program.

2. Private: Members marked as private can only be accessed within the class in which they are declared. They are not accessible from outside the class.

3. Protected: Members marked as protected can be accessed within the class in which they are declared and also from subclasses (classes that inherit from the class in which the protected members are declared).

In general, it is a good practice to make data members private and provide public methods to access and modify them. This is known as the principle of encapsulation, which helps to protect the internal state of the object and promotes modularity, reusability, and maintainability of code.

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30. What is data abstraction?

Data abstraction is one of the most important features of OOPs. It only allows important information to be displayed. It helps to hide the implementation details.

For example, while using a mobile, you know, how can you message or call someone but you don't know how it actually happens.

This is data abstraction as the implementation details are hidden from the user.

32. How to achieve data abstraction?

Data abstraction can be achieved using two ways:

• Abstract class
• Abstract method

33. What is an abstract class?

An abstract class is also a class which is consists of abstract methods.

So what is an abstract method?

These methods are basically declared but not defined and If these methods need to be used later in some subclass that time those methods have to be exclusively defined in the subclass.

34. Differentiate between data abstraction and encapsulation.

Data abstraction refers to the process of providing a simplified view of data to the user, without exposing the underlying implementation details. It involves separating the essential characteristics of data from the implementation details, so that the user can focus on the essential features without being overwhelmed by the implementation details.

Encapsulation, on the other hand, refers to the process of bundling data and functions that operate on that data within a single unit, or object. In other words, it involves wrapping up of data and functions into a single unit, which can be accessed and modified only through a well-defined interface.

In summary, data abstraction deals with providing a simplified view of data, while encapsulation deals with bundling data and functions into a single unit. Both data abstraction and encapsulation are important concepts in object-oriented programming, and are used to promote modularity, reusability, and maintainability of code.

34. What are virtual functions?

Virtual functions are also part of the functions which are present in the parent class and they are overridden by the subclass. These functions help to achieve runtime polymorphism.

36. What is a destructor?

A destructor is a method that is called automatically when an object is destroyed.

The destructor also recovers the heap space which was allocated to the destroyed object. It also start closing the files and database connections of the object, etc.

37. What is a copy constructor?

By copying the members of an existing object, the copy constructor initialises the members of a newly formed object. The argument for the copy constructor is a reference to an object of the same class. Programmers have the option of directly defining the copy constructor. The compiler defines the copy constructor if the programmer doesn't.

38. What is the use of 'finalize'?

Finalize is used to free the unmanaged resources and also help to clean before Garbage Collection(GC). It performs memory management tasks.

39. What is Garbage Collection(GC)?

Programming languages like C# and Java include garbage collection (GC) as a memory recovery mechanism. A programming language that supports garbage collection (GC) contains one or more GC engines that automatically release memory space that has been reserved for things the application is no longer using.

40. What is a final variable?

A final variable can only receive one explicit initialization. A reference variable that has been marked as final is unchangeable in its object reference. The data included in the object, however, can be modified. As a result, while the object's state can be altered, its reference cannot.

41. What is an exception?

An exception is a kind of message that interrupts and comes up when there is an issue with the normal execution of a program. Exceptions provide an error and transfer it to the exception handler to resolve it. The state of the program is saved as soon as an exception is raised.

42. What is exception handling?

Exception handling in Object-Oriented Programming is the most important concept. It is used to manage errors. An exception handler help to throw errors and then catch the error in order to solve them.

43. What is the difference between an error and an exception?

44. What is a try/ catch block?

The terms "try" and "catch" describe how to handle exceptions brought on by coding or data mistakes while a program is running. The section of code where exceptions occur is called a try block. Exceptions from try blocks are caught and handled in a catch block.

45. What is a finally block?

Finally designates the section of code that works with the try keyword. It specifies code that is always executed before the method is finished, immediately behind the try and any catch blocks. Regardless of whether an exception is thrown or caught, the finally block is always executed.

46. Can you call the base class method without creating an instance?

Yes, you are allowed to call the base class without instantiating it but there are some conditions that are applicable:

• If it is a static method
• The base class is inherited by some other subclass

47. What is the difference between OOP and SOP?

The key distinction between structured and object-oriented programming is that the former allows for the creation of programs using a collection of modules or functions, whilst the latter allows for the construction of programs using a collection of objects and their interactions.

Object-oriented programming involves concepts of objects and classes. Everything is considered as an object which has specific properties and behaviours which are represented in a class. Object-oriented programming provides encapsulation and abstraction in the code. Ex: – Java Programming language.

Structure-oriented programming involves the concepts of functions and structures. Everything is considered functionality and structures, represented using functions—Ex: – C Programming language.

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

Any real-world entity is called an object. The object has specific properties and behaviours, and the similar type of objects having similar features and behaviours are grouped as a class. Hence, Class is a blueprint of objects, and an object is an instance of a class.

Ex: –  

1. An Animal is a class, and cat, dog, etc., are objects with common properties like name, type, and common behaviors like speaking, walking, running, etc.

2. Mobile is a class, and Nokia, moto, iPhone, etc., are objects with common properties like modal_no, color, etc., and common behaviors like audio_calling, video_calling, music, etc.
   

   49.What are 'access specifiers'?

Access specifiers are the keywords in any programming language used to specify the Class's, method's, interface's and variable's behaviour concerning its accessibility. The access specifiers in C++ Programming are public, private, and protected.

50. Can you create an instance of an abstract class?

No, an instance of the Abstract class cannot be created. To implement the abstract Class, abstract methods, the Abstract Class should be extended by another class, and the object of the implementation class can be created.