Top most OOP Concepts: most asked interview Question and answer for Freshers

Top most OOP Concepts : The programming paradigm known as OOP (Object-Oriented Programming) represents actual items as objects. These things have behaviours (methods) and properties (attributes). OOP encourages modularity, maintainability, and code reuse.

A programmer with expertise in designing, creating, and managing software programs utilizing object-oriented programming principles is known as an OOP developer.

here are some Top most OOP Concepts: most asked interview Question and answer for Freshers

1.What is the purpose of using OOPs concepts?

Creating code that is more modular, reusable, and maintainable is the basic goal of object-oriented programming, or OOP. Object-oriented programming (OOP) facilitates a more structured and effective approach to software development by decomposing intricate problems into smaller, self-contained items.

Encapsulation, inheritance, and polymorphism are examples of OOP ideas that offer strong modeling tools for real-world entities and their interactions. By controlling access and concealing internal implementation details, encapsulation protects the integrity of data. While polymorphism promotes flexibility and extensibility by treating objects of different kinds as though they were of the same type, inheritance allows for code reuse by establishing hierarchies of related classes.

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2.What are the advantages and disadvantages of OOP?

Advantages of OOP

• It takes a bottom-up methodology.
• It is a good representation of the genuine word.
• It makes code reusability possible.
• uses abstraction to protect the user from needless data exposure.
• OOP compels designers to engage in a protracted and thorough design process, which produces better work with fewer errors.
• Break up a complicated issue into manageable parts.
• Programmers can accomplish their objectives more quickly.
• reduces the intricacy.
• Code may be easily extended and redesigned without affecting other features.

Disadvantages of OOP

• It needs to be planned properly.
• The design of a program is difficult.
• A programmer needs to be well qualified.
• Classes are frequently unnecessarily broad.

3.What do you understand by class and object?

A class is a set of rules or specifications that specify the traits and actions of a collection of objects. It contains information (attributes) and operations (methods) shared by all objects of that kind. Comparable to a cookie cutter, a class specifies the dimensions and form of the cookies but is not a cookie in and of itself.

An instance of a class is called an object. It symbolizes a particular thing or idea that follows the class’s established blueprint. Creating an object is like filling in a cookie cutter with certain values for its characteristics. Although every object has a different set of data, they are all made up of the same class-defined methods.

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4.What is the concept of access specifiers when should we use these?

Access specifiers are reserved keywords in OOP languages that are used to set the accessibility of classes, methods, and other class members. Another name for it is access modifiers. Public, private, and protected are all included. There is one more language-specific access specifier. Java, for example, has a different default access specifier. These access specifiers are essential to encapsulation, one of the main purposes of OOP. The accessibility is shown in the following table.

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5.What is composition?

An object-oriented programming notion known as composition symbolizes a “has-a” relationship between objects. It involves an object that is made up of or contains other objects. An automobile “has a” wheel, engine, and transmission, for instance. In composition, the contained object is only an element that enhances the functioning of the containing object; it does not become part of its identity.

You may write more modular and reusable code by utilizing composition. It is possible to change or replace a component on its own without impacting the containing object. This facilitates the extension and maintenance of your code.

6. What are the differences between copy constructor and assignment operator?

When an object is created using another object of the same class, the copy constructor is immediately called. It is employed to initialize a new object with an existing object’s values. For instance, the class’s copy constructor is invoked to replicate the values from object obj1 to object obj2, when you create a new object obj2 using object obj1.

To assign the values of one object to another already-existing object, use the assignment operator. When you use the = operator to join two objects of the same class, it is called. To replicate the values from obj1 to obj2, for instance, use the assignment operator when obj2 = obj1.

The primary distinction is in the order in which they are called: the assignment operator is invoked after the object has already been constructed, whereas the copy constructor is called while the object is being built. Furthermore, an object is normally initialized using the copy constructor, and modified using the assignment operator.

7. What is meant by Structured Programming?

Structured programming is a programming paradigm that emphasizes the use of a disciplined approach to software development, focusing on control flow and code organization. It aims to improve code readability, maintainability, and reliability by promoting the use of specific programming constructs and avoiding the use of goto statements.

8.What are access specifiers and what is their significance?

In object-oriented programming languages, access specifiers are keywords that regulate a class member’s (attributes and methods) visibility from other program sections. They ascertain whether access to a member is possible from classes in the same package, from classes outside of it, or from within the class itself.

A key component of object-oriented programming is encapsulation, which requires access specifiers. You may safeguard your classes’ internal implementation details and avoid unintentional changes by carefully regulating class member visibility. This enhances the reusability, maintainability, and security of the code.

9.Define a superclass?

A superclass is a class that acts as a template for other classes. It is sometimes referred to as a parent class or base class. It outlines shared properties and functions that its offspring classes are able to inherit. Consider a superclass as a broad template upon which smaller specialized classes are built.

For instance, a superclass named Animal may define methods like eat and walk, as well as characteristics like name, species, and weight. Subclasses such as Dog, Cat, and Bird can add their own unique behaviors and features to Animal’s methods and attributes, but they can also inherit them.

10.What is meant by static polymorphism?

The compiler chooses which method to call in a static polymorphism, sometimes referred to as method overloading, based on the quantity and kind of arguments supplied to it during compilation. This indicates that the choice of the method to use is decided upon prior to the application running.

Several methods with the same name but distinct argument lists can be found in the same class to accomplish static polymorphism. Based on the precise arguments supplied during the method call, the compiler chooses the relevant method. Because you may build methods with varied signatures to accommodate diverse input conditions, this enables more expressive and adaptable code.

11.What is the difference between overloading and overriding?

overloading : Determining how many methods to define in a class with the same name but distinct parameter lists is called overloading. This lets you write methods that take different inputs and accomplish the same job in different ways. Based on the precise inputs supplied during the method invoc12ation, the compiler chooses which method to invoke. Static polymorphism is exemplified by overloading, wherein the choice is made during compilation.

overriding :When a subclass offers an alternative implementation of a method that is already specified in its superclass, this is known as overriding. This lets you modify inheriting methods’ behavior to fit the particular requirements of the subclass. The superclass and subclass must have the same method signature (name, parameters, and return type). Since the selection of which method to call is done at runtime based on the actual type of the object, overriding is a type of dynamic polymorphism.

12 . What is an abstract class?

A class that is not directly instantiable is called an abstract class. It defines a common structure and behavior and acts as a template for other classes. Abstract methods, or methods defined without a body, are frequently seen in abstract classes. Concrete subclasses that extend the abstract class are required to implement abstract methods.

Abstract classes are mostly used to enforce a certain degree of consistency and organization by giving related classes a shared interface. They are frequently employed to define base classes or abstract ideas that are not fully realizable on their own. You may encourage code modularity, maintainability, and reusability by developing abstract classes.

13.What is an exception?

An exception is an unforeseen circumstance that arises while a program is being executed and interferes with its regular flow. The program passes control to a designated error-handling mechanism in the event of an exception. This keeps the program from crashing and enables you to handle unforeseen circumstances with grace.

Several things, including erroneous user input, file I/O issues, network outages, and programming faults, can result in exceptions. They are frequently depicted as objects that hold details about the error, like the kind of exception, a description, and the place it happened. You can increase the robustness and dependability of your software and make it more user-friendly and resistant to unforeseen events by managing exceptions well.

14.What is meant by Garbage Collection in OOPs world?

One type of automatic memory management found in object-oriented programming languages is garbage collection. It is a procedure that recognizes and recovers memory that the program is no longer using automatically. Upon creation, items in memory are allotted a predetermined amount of space. An object becomes garbage and can be safely removed if it is no longer referenced by any portion of the application.

Periodically, the garbage collector looks through the memory heap to find items that are no longer accessible. The memory that these objects had taken up was then freed up for future allocations. By appropriately deallocating unwanted objects, this method helps prevent memory leaks, which can result in excessive memory usage and possible performance problems.

15. What is Encapsulation?

An essential component of object-oriented programming is encapsulation, which is the grouping of data (attributes) and the methods (functions) that manipulate them into a single unit known as a class. This ensures data integrity, guards against accidental changes, and shields an object’s internal state from outside meddling.

By encapsulating related data and activity into a clearly defined class, encapsulation encourages modularity and reusability. Because modifications to a class’s internal implementation may be done without impacting other areas of the program, this facilitates code management and maintenance. Encapsulation also helps strengthen code security by guarding against unwanted access to private information.

16.What is inheritance?

A key idea in object-oriented programming is inheritance, which lets you build new classes (subclasses) off of preexisting classes (superclasses). Subclasses allow for code reuse and the creation of hierarchies of related classes by inheriting the properties and methods of their superclass.

This idea promotes code modularity and structure since shared traits and behaviors may be specified in a superclass and then further specialized in subclasses. Additionally, polymorphism—the ability to treat objects of various subclasses as though they were of the same type—is made possible by inheritance, which gives your code greater adaptability and versatility.

17.What is a destructor?

In object-oriented programming, a destructor is a unique member function that is called automatically when an object is destroyed. Before the garbage collector reclaims the object’s memory, it is utilized to carry out any necessary cleanup operations. Usually, destructors are used to remove resources—like file handles, network connections, or dynamically allocated memory—that were acquired by the object during its lifespan.

In order to maintain appropriate resource management and stop memory leaks, destroyers are necessary. You can prevent unexpected side effects and preserve the integrity of your software by releasing resources on time. Destructors can be manually called in some circumstances, but they are automatically called when an object is removed explicitly or goes out of scope.

18. What is the use of ‘finalize’?

In object-oriented programming languages such as Java, the garbage collector automatically calls a special method called finalize() prior to an object being reclaimed. It is intended to be a last-ditch attempt to complete cleanup jobs that other mechanisms, such destructors, might not have been able to finish.

However, because of its instability and possible performance overhead, using finalize() is generally advised. The finalize() function may not be run at all, and the garbage collector’s timing is erratic. Furthermore, using finalize() for important cleanup operations could result in unexpected behavior and make maintaining your code more difficult.

To guarantee that resources are released consistently and predictably, it is usually advised to employ deterministic resource management strategies, such as try-finally blocks or explicit calls to close() methods. Using these techniques instead of depending on finalize() gives you greater control and dependability.

19. What is a try/ catch block?

A programming construct called a try/catch block is used to handle exceptions gracefully. The catch block handles the exception by providing custom code to be executed in the event of an error, whereas the try block contains code that might throw an exception. This helps prevent the program from crashing unexpectedly and ensures that the application can continue running even in the face of errors.

You can increase your software’s robustness and dependability by utilizing try/catch blocks. You can take corrective action to fix the mistake, report exceptions for debugging, or give the user helpful error messages. This contributes to the development of a robust and user-friendly application.

20.What are pure virtual functions?

Special member functions declared within an abstract class are known as pure virtual functions. They make a declaration, but they don’t follow through. Pure virtual functions are meant to compel subclasses to supply their own implementation of these techniques.

You are essentially constructing a contract that subclasses must abide by when you declare a method as pure virtual. This guarantees that every subclass implements the necessary functionality and has a consistent interface. In order to establish a common behavior for a collection of related classes without offering a concrete implementation, pure virtual functions are frequently used to create abstract base classes. This encourages flexibility and code reuse because subclasses can alter the behavior as required.