Top 10 Interview Questions on OOPS

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Published: 21st December 2010
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Top 10 .Net Interview Questions and Answers on OOPS





1. What is an Object in OOPS?





An object is a software bundle of variables and related methods. Objects are related to real life scenario. Class is the general thing and object is the specialization of general thingObjects is instance of classes.





Declaration of an Object in OOPs





ClassName objectName=new ClassName();





E.g.: Person objPerson= new Person();





An object is characterized by concepts like:





Attribute





Behavior





Identity














2. What is an Attribute in OOPs?





Attributes define the characteristics of a class.





The set of values of an attribute of a particular object is called its state.





In Class Program attribute can be a string or it can be a integer














3. What is a Behavior in OOPS?





Every object has behavior





In C#, behaviors of objects are written in methods.





If a behavior of an object needs to be performed, then the corresponding method is called.














4.What is an Identity in OOPS?





Each time an object is created the object identity is been defined.





This identity is usually created using an identifier which is derived from the type of item














5.What is Encapsulation in OOPS?





Encapsulation is one of the fundamental principles of object-oriented programming.





Encapsulation is a process of hiding all the internal details of an object from the outside world





Encapsulation is the ability to hide its data and methods from outside the world and only expose data and methods that are required





Encapsulation is a protective barrier that prevents the code and data being randomly accessed by other code or by outside the class





Encapsulation gives us maintainability, flexibility and extensibility to our code.





Encapsulation makes implementation inaccessible to other parts of the program and protect from whatever actions might be taken outside the function or class.





Encapsulation provides a way to protect data from accidental corruption





Encapsulation hides information within an object





Encapsulation is the technique or process of making the fields in a class private and providing access to the fields using public methods





Encapsulation gives you the ability to validate the values before the object user change or obtain the value





Encapsulation allows us to create a "black box" and protects an objects internal state from corruption by its clients.





There are two ways to create a validation process.





1.Using Assessors and Mutators





2.Using properties





Benefits of Encapsulation





In Encapsulation fields of a class can be read-only or can be write-only





A class can have control over in its fields





A class can change data type of its fields anytime but users of this class do not need to change any code

















6.What is Inheritance in OOPS?





Inheritance, together with encapsulation and polymorphism, is one of the three primary characteristics (concept) of object-oriented programming





Inheritance enables you to create new classes that reuse, extend, and modify the behavior that is defined in other classes





The Class whose methods and variables are defined is called super class or base class





The Class that inherits methods and variables are defined is called sub class or derived class





Sometimes base class known as generalized class and derived class known as specialized class





Keyword to declare inheritance is ":" (colon) in visual c#





Benefits of using Inheritance





Once a behavior (method) or property is defined in a super class(base class),that behavior or property is automatically inherited by all subclasses (derived class).





Code reusability increased through inheritance





Inheritance provide a clear model structure which is easy to understand without much complexity





Using inheritance, classes become grouped together in a hierarchical tree structure





Code are easy to manage and divided into parent and child classes

















7. What is Polymorphism in OOPS?





Polymorphism is one of the primary characteristics (concept) of object-oriented programming





Poly means many and morph means form. Thus, polymorphism refers to being able to use many forms of a type without regard to the details





Polymorphism is the characteristic of being able to assign a different meaning specifically, to allow an entity such as a variable, a function, or an object to have more than one form





Polymorphism is the ability to process objects differently depending on their data types





Polymorphism is the ability to redefine methods for derived classes.





Types of Polymorphism





Compile time Polymorphism





Run time Polymorphism

















8. What is Compile Time Polymorphism in OOPS?





Compile time Polymorphism also known as method overloading





Method overloading means having two or more methods with the same name but with different signatures

















9. What is Run Time Polymorphism in OOPS?





Run time Polymorphism also known as method overriding





Method overriding means having two or more methods with the same name , same signature but with different implementation

















10. What is Access Modifier in OOPS?





Access modifiers determine the extent to which a variable or method can be accessed from another class or object





The following five accessibility levels can be specified using the access modifiers





Private





Protected





Internal





Protected internal





Public

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