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Best 50 Software Programming Interview Questions & Answers
May 27, 2015 Career News

1. What is the difference between an Interface and an Abstract class?

Answer: An abstract class can have instance methods that implement a default behavior. An Interface can only declare constants and instance methods, but cannot implement default behavior and all methods are implicitly abstract. An interface has all public members and no implementation. An abstract class is a class which may have the usual flavors of class members (private, protected, etc.), but has some abstract methods.

2. What is the typical use of Hashtable?

Answer: Whenever a program wants to store a key value pair, one can use Hashtable.

3. What is a primary key? What is a foreign key?

Answer: A primary key is the field(s) in a table that uniquely defines the row in the table; the values in the primary key are always unique. A foreign key is a constraint that establishes a relationship between two tables. This relationship typically involves the primary key field(s) from one table with an adjoining set of field(s) in another table (although it could be the same table). The adjoining field(s) is the foreign key.


4. What is the difference between static and non-static variables?

Answer: A static variable is associated with the class as a whole rather than with specific instances of a class. Non-static variables take on unique values with each object instance.


5. What is Externalizable interface?

Answer:Externalizable is an interface which contains two methods readExternal and writeExternal. These methods give you a control over the serialization mechanism. Thus if your class implements this interface, you can customize the serialization process by implementing these methods.


6. What is the Set interface?

Answer: The Set interface provides methods for accessing the elements of a finite mathematical set. Sets do not allow duplicate elements.


7. What does NULL mean?

Answer: The value NULL is a very tricky subject in the database world, so don’t be surprised if several applicants trip up on this question.  The value NULL means UNKNOWN; it does not mean ” (empty string). Assuming ANSI_NULLS are on in your SQL Server database, which they are by default, any comparison to the value NULL will yield the value NULL. You cannot compare any value with an UNKNOWN value and logically expect to get an answer. You must use the IS NULL operator instead.


8. What is the common usage of serialization?

Answer: Whenever an object is to be sent over the network, objects need to be serialized. Moreover if the state of an object is to be saved, objects need to be serialized.


9. Which operating system has the .NET Framework and Common Language Runtime (CLR) natively installed?

Answer: CLR natively installed on a Windows XP professional and newest operating systems


10. What is the difference between a while statement and a do statement?

Answer: A while statement checks at the beginning of a loop to see whether the next loop iteration should occur. A do statement checks at the end of a loop to see whether the next iteration of a loop should occur. The do statement will always execute the body of a loop at least once.


11. What is the difference between bug priority & bug severity?

Answer:  HiPrority : Urgency Of the BugSeverity : Impact of the Bug


12. What is the Collection interface?

Answer: The Collection interface provides support for the implementation of a mathematical bag – an unordered collection of objects that may contain duplicates.


13. How can one prove that the array is not null but empty?

Answer:  Print args.length. It will print 0. That means it is empty. But if it would have been null then it would have thrown a NullPointerException on attempting to print args.length.

14. What is UML?

Answer: Unified Modeling Language (UML) is a standardized general-purpose modeling language in the field of software engineering. UML includes a set of graphical notation techniques to create abstract models of specific systems.

“The Unified Modeling Language (UML) is a graphical language for visualizing, specifying, constructing, and documenting the artifacts of a software-intensive system.

The UML offers a standard way to write a system’s blueprints, including conceptual things such as business processes and system functions as well as concrete things such
as programming language statements, database schemas, and reusable software components.” OMG Specification

15. How would you use jQuery in ASP.NET Pages?

1.JQuery is officially endorsed by Microsoft ASP.NET team and ships with Microsoft plans to ship the JQuery JavaScript library with its Visual Studio developer tool suite.
2.JQuery is open source and can be downloaded freely from
3. jQuery is JavaScript library and can be used by simple referece of js files on your ASP.NET pages
4. The best place to do so is master page…

16. What are the callback methods in Entity beans?

Answers: Callback methods allows the container to notify the bean of events inits life cycle. The callback methods are defined in the javax.ejb.EntityBean interface…………


17. What is conversion constructor?

Answers:  Conversion constructor is a constructor with a single argument makes that constructor as conversion actor and it can be used for type conversion.

for example:

class Boo
Boo( int i );

Boo BooObject = 10 ; // assigning int 10 Boo object


18. What is SOAP?

Answers: SOAP is an XML-based messaging technology standardized by the W3C, which specifies all the necessary rules for locating Web services, integrating them into applications, and communicating between them.


19. What is the Locale class?

Answers: The Locale class is used to tailor program output to the conventions of a particular geographic, political, or cultural region.


20. What is SDLC (Software Development Life Cycle)?


SDLC (Software Development Life Cycle) is the process of developing software through business needs, analysis, design, implementation and maintenance. Software has to go through various phases before it is born which are as follows:

(i)Generating a Concept – A concept comes from the users of the software. For example, a Pizza Hut may need software to sell pizza.

An Indian store may need software to sell its newly arrived movies or grocery. The owner of the company feels that he needs software that would help him in tracking his expenses and income as well as enhance the selling process. This is how the concept is generated. The owner will specifically tell the software company what kind of software he would need. In other words, he will specify his requirements.

(ii) Requirements analysis – After the owner (user) knows his requirements, then it is given to a software team (company) who will analyze the requirement and prepare requirement document that will explain every functionality that are needed by the owner. The requirement document will be the main document for developers, testers and database administrators. In other words, this is the main document that will be referred by everyone. After the requirement documents, other detailed documents many be needed. For example, the architectural design which is a blueprint for the design with the necessary specifications for the hardware, software, people and data resources.

(iii) Development: After the detailed requirement documents (some companies have design documents instead of requirement documents), the developers start writing their code (program) for their modules. On the other hand, the testers in the QA (Quality Assurance) Department start writing Test Plans (one module=1 test plan), test cases and get ready for testing.

(iv) Testing: Once the code (programs) are ready, they are compiled together and to make a build. This build is now tested by the software testers (QA Testers)

(v) Production: After testing, the application (software) goes into production (meaning, it will be handed over to the owner).

(vi) End: And one day, the owner will have say bye to the software either because the business grows and this software does not meet the demand or for some reason, the he does not need the software. That’s the end of it.

21. What is namespace of mvc?


ASP.NET MVC namespaces and classes are located in the System.Web.Mvc assembly.

System.Web.Mvc namespace
Contains classes and interfaces that support the MVC pattern for ASP.NET Web applications. This namespace includes classes that represent controllers, controller factories, action results, views, partial views, and model binders.

System.Web.Mvc.Ajax namespace
Contains classes that support Ajax scripts in an ASP.NET MVC application. The namespace includes support for Ajax scripts and Ajax option settings.

System.Web.Mvc.Async namespace
Contains classes and interfaces that support asynchronous actions in an ASP.NET MVC application

System.Web.Mvc.Html namespace
Contains classes that help render HTML controls in an MVC application. The namespace includes classes that support forms, input controls, links, partial views, and validation.




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