Please navigate to the bottom of the page for Table of Contents

Saturday, June 18, 2011

Basic JAVA interview questions

Having covered a lot of topics in .NET, let’s shift our attention to some JAVA questions. In this post, we will cover a few basic JAVA interview questions to get started. We will advance in complexity in later posts.

SO, first, let’s start with constructors.

Question: What is the difference between constructors and other regular methods?

Constructors must have the same name as the class name and cannot return a value. The constructors are called only once per creation of an object while regular methods can be called many times.

Question: What happens if you do not provide a constructor?

Java does not actually require an explicit constructor in the class description. If you do not include a constructor, the Java compiler will create a default constructor in the byte code with an empty argument. If a class includes one or more explicit constructors, the java compiler does not create the default constructor.

Question: Can you call one constructor from another?

Yes, the key is to use the this() construct.

public Shape(int id) {
this.id = id; // "this" means this object
}

public Shape(int id, String type) {
this(id); // calls constructor public Shape(int id)
this.type = type; // "this" means this object
}



Question: How can you invoke the base class constructor in the derived class?


You can use the super() syntax. Note that this has to be the first statement in the function.


public Circle(int id) {
super(id); //must be the very first statement in the constructor.
}



Question: How can you invoke base class methods in the derived class?


To call a regular method in the base class use “super.myMethod( )”. This can be called at any line.


public class Circle extends Shape 
{
public void setUp()
{
super.initialize();
// do circle stuff
}
}



public void reset() throws Throwable
{
try
{
// Do stuff here to rest your object
}
catch (Throwable t) {}
finally
{
super.reset(); //clean up your parent class. Unlike constructors super.regularMethod() can be called at any line.
}
}



Question: Explain static initializers with an example.


When a class is loaded, all blocks that are declared static and don’t have function name (i.e. static initializers) are executed even before the constructors are executed. As the name suggests they are typically used to initialize static fields.


public class StaticInitializer 
{
public static final int x = 5;
public static final int y;
//note that since y is final, it can be initialized only once.

//Static initializer block, which is executed only once when the class is loaded.
static
{
if(x == 5)
y = 10;
else
y = 5;
}

//constructor is called only after static initializer block
public StaticInitializer(){}
}


The code above sets the value of x to 5 and y to 10.

96 comments:

  1. Given stuff and logical thinking are very good!

    ReplyDelete
  2. When coming to the java point there will be definitely asking the Questions
    on the constructors!So i hope this is the good introduction for the java questions!

    ReplyDelete
  3. ya this is very very important to the interview, because constructors are the base for the objects creation....

    ReplyDelete
  4. This comment has been removed by a blog administrator.

    ReplyDelete
  5. Write a program where the user enters the number of asterisk for the first row printed. The user will then enter another number (that is less than the number entered first). This number will be the number that each row will be decreased by. For example: User will enter 8 first and 3 second (row 1 - 8 asterisks, row 2 - 5 asterisks, row 3 - 2 asterisks. What will be printed is:

    ********
    *****
    **
    You can't print less asterisks than the decrement value (in the example you can't go below 2 because 3 was the decrement number).

    ReplyDelete
    Replies
    1. This is quite simple:
      static void PrintStars(int startCount, int decrementValue)
      {
      // error checks
      if ((startCount > 0) && (startCount >= decrementValue))
      {
      while (startCount >= 0)
      {
      // print current star count
      Console.WriteLine(new String('*', startCount));

      // decrement for next round
      startCount -= decrementValue;
      }
      }
      else
      {
      Console.WriteLine("Please provide valid input values");
      }
      }

      Delete
    2. Sain Bainuu,


      Thank you! Thank you! Thank you! Your blog was a total game changer!


      Hello people, So I am having trouble uploading a file to my bucket. I have the proper credentials all set. The problem is when I try doing a
      putRequest('bucket', 'keyName', 'fileFullPath') it will only save the file name and not the bytes. So I try sending it as an input stream to a byte array. This way it says there is no such file at specified location? I am running linux so It says no specified file at /home/{user}/pictures/example.jpg This is the problem I believe because it is searching from /home and not /




      It was cool to see your article pop up in my google search for the process yesterday. Great Guide.
      Keep up the good work!


      Thanks a heaps,

      Delete
  6. Copper Wire Co. sells spools of copper wiring for $100 each. Write a program that display the status of an order. The program should have a function that asks for the following information:

    The number of spools ordered.
    The number of spools in stock.
    If there are special shipping and handling charges.

    (Shipping and handling is normally $10 per spool.) If there are special charges, it should ask for the special chargers per spool.

    Output: number of spools shipped, number of spools back ordered, subtotal of portion ready to ship, total shipping and handling charges on portion ready to ship, total of order ready to ship.

    Validate: do not accept numbers less than one for spools ordered. Do not accept a number less than 0 for spools in stock or shipping and handling charges.

    Once an order is printed, ask the user for the next order. Use a sentinel value to stop (q for quit or -1)

    ReplyDelete
  7. I came across your guide and found exact Basic-java Interview Q/A’s which I was looking for. Thanks for such a useful information’s. But I had found one good website related to Java interview Q/A’s. More Info: java-interview-questions

    ReplyDelete
  8. Thanks for sharing such agreat article, really very helpful information. Keep sharing.

    Best Software company in New jersey, USA

    ReplyDelete


  9. wow...nice blog, very help full information. Thanks for sharing.

    ReplyDelete

  10. Grate blog to read its very nice explanation about Internet Of Things
    Internet Of Things

    ReplyDelete
  11. Very good informative article. Thanks for sharing such nice article, keep on up dating such good articles.
    Best Cloud Solutions | Austere Technologies

    ReplyDelete
  12. Really great blog, it's very helpful and has great knowledgeable information. Thanks for sharing, keep updating such a good informative blog.

    Quality Managment Services | Austere Technologies

    ReplyDelete
  13. Very good informative article. Thanks for sharing such nice article, keep on up dating such good articles
    Austere Technologies|Mobility

    ReplyDelete
  14. Great article, really very helpful content you made. Thank you, keep sharing.

    Best Software Testing Services | Austere Technology

    ReplyDelete
  15. Thanks for sharing this informative article..!!
    Keep posting waiting for next post.

    iOS Training in Bangalore Java Training in Bangalore

    ReplyDelete
  16. Very useful information Big Classes has been constantly pioneering and evolving in the Online Training Industry. With an experience of over a decade and half in the training industry, Big Classes is today a name to be reckoned with for any kind of IT trainings in online model. With an army of trainers and a wide array of courses, Big Classes guarantees high quality training at an extremely competitive price, ensuring 100% value for money.
    Online IT Training

    ReplyDelete
  17. I like your blog, I read this blog please update more content on hacking,
    Nice post,and good information Thanks for sharing further check it once at
    .NET Online Course

    ReplyDelete
  18. Wow...What an excellent informative blog, really helpful. Thank you. Best Oracle DBA Course Training| orskl
    Orskl

    ReplyDelete
  19. It was thinking about whether I could utilize this review on my other site, I will connect it back to your site though.Great Thanks. basic English vocabulary

    ReplyDelete
  20. Wow...What an excellent informative blog, really helpful. Thank you. Best Oracle DBA Course Training| orskl

    ReplyDelete
  21. The information is meaningful and magnificent which is shared here about the article. I really thank you for such a innovative post. if you want to take training in java, then ratindia.com is best for you. Summer internship program in jaipur

    ReplyDelete
  22. Next time I read a blog, Hopefully it won't fail me as much as this one. I mean, I know it was my choice to read, but I truly thought you would have something interesting to say. All I hear is a bunch of complaining about something that you could possibly fix if you weren't too busy seeking attention.
    best service center in marathahalli

    Samsung Galaxy S9+ authorized service center near me

    oppo A77 service center near me

    oneplus 5T authorized service center in banglore

    realme 2 Pro authorized service center in banglore

    ReplyDelete
  23. This comment has been removed by the author.

    ReplyDelete
  24. It's a nice article, Which you have shared here about the java. Your article is very useful for those who are want to learn java programming course. I would like to thanks for sharing this post here. Best Core Java With Data Structures Course In Delhi

    ReplyDelete
  25. For Devops training in Bangalore visit:Devops training in Bangalore

    ReplyDelete
  26. Excellent web site you have got here.. It’s difficult to find good quality writing like yours these days.
    best service center bangalore
    I really appreciate individuals like you! Take care!!
    Vivo display replacement Marathahalli
    This is a topic that's near to my heart... Cheers! Exactly where are your contact details though?
    Motorola display replacement Marathahalli

    ReplyDelete
  27. I seriously love your site.. Great colors & theme. Did you develop this website yourself?
    Huawei display replacement Marathahalli
    Please reply back as I’m looking to create my own website and would like to learn where you got this from or what the theme is named. Kudos!
    Asus display replacement Marathahalli
    Everyone loves it whenever people get together and share ideas. Great website, stick with it!
    LG display replacement Marathahalli

    ReplyDelete
  28. The article explains value of Java and it is role inside Information Technology sector. It highlights the key role that Java plays in creating Online Advanced JAVA Training

    ReplyDelete
  29. This comment has been removed by the author.

    ReplyDelete
  30. Very useful blog. excellent Information . Thank you . keep sharing
    Best BBA College in Hyderabad

    ReplyDelete
  31. This comment has been removed by the author.

    ReplyDelete
  32. ethical hacking is the upcoming, valuable and job oriented solution that IT companies and other industrial sectors are adapting today. machine learning courses in hyderabad

    ReplyDelete
  33. The blog or and best that is extremely useful to keep I can share the ideas of the future as this is really what I was looking for, I am very comfortable and pleased to come here. Thank you very much. i appreciate your efforts taken for the same. I found this worth sharing and must share this with all.

    digital marketing company in bhubaneswar
    website design and development

    ReplyDelete
  34. I am so happy to found your blog post because it's really very informative. Please keep writing this kind of blogs and I regularly visit this blog. Have a look at my services.
    Cyber Security Training Course in Chennai | Certification | Cyber Security Online Training Course | Ethical Hacking Training Course in Chennai | Certification | Ethical Hacking Online Training Course | CCNA Training Course in Chennai | Certification | CCNA Online Training Course | RPA Robotic Process Automation Training Course in Chennai | Certification | RPA Training Course Chennai | SEO Training in Chennai | Certification | SEO Online Training Course

    ReplyDelete
  35. Thank you for taking the time to provide us with your valuable information. We strive to provide our candidates with excellent care and we take your comments to heart.As always, we appreciate your confidence and trust in us.This is an awesome post.Really very informative and creative contents. These concept is a good way to enhance the knowledge.I like it and help me to development very well.Thank you for this brief explanation and very nice information.Well, got a good knowledge.
    DevOps Training in Chennai

    DevOps Online Training in Chennai

    DevOps Training in Bangalore

    DevOps Training in Hyderabad

    DevOps Training in Coimbatore

    DevOps Training

    DevOps Online Training

    ReplyDelete
  36. 1. PHP VS Java: Performance & Speed. In a nutshell: While comparing the Java vs PHP performance, Java is clearly a winner as it is faster and efficient than PHP to write enterprise applications. Like developers have to build mobile enterprise applications to streamline complex business processes and operation
    Java Training in Chennai

    Java Training in Bangalore

    Java Training in Hyderabad

    Java Training in Coimbatore

    Java Training

    ReplyDelete
  37. This is a fabulous post I seen because of offer it. It is really what I expected to see trust in future you will continue in sharing such a mind boggling post
    Digital Marketing Training Institutes in Hyderabadad

    ReplyDelete
  38. This comment has been removed by the author.

    ReplyDelete
  39. I like this post,And I figure that they making some incredible memories to scrutinize this post,they may take a good site to make an information,thanks for sharing it to me
    certification of data science

    ReplyDelete
  40. You totally coordinate our desire and the assortment of our data.
    data science course delhi

    ReplyDelete
  41. Thanks for sharing this post.
    This article really useful for me and I learn a lot of things from this blog.
    I am working as a freelance full stack developer

    ReplyDelete
  42. Great blog post,
    Digital Marketing is right now the most stable job you could have. There are many openings for Digital Marketers around the globe. Hence we suggest you to attend our Digital Marketing Course in Hyderabad to acquire skills that a Digital Marketer needs.

    ReplyDelete
  43. Thank you so much for sharing all this wonderful information !!!! It is so appreciated!! You have good humor in your blogs. So much helpful and easy to read!
    Java Training in Pune

    ReplyDelete
  44. Thank you quite much for discussing this type of helpful informative article. Will certainly stored and reevaluate your Website.

    AWS Training in Hyderabad

    ReplyDelete
  45. Nice and very informative blog, glad to learn something through you.
    ai course in aurangabad

    ReplyDelete
  46. Nice blog. it is very nice java question of interview. keep it up, Thanks for sharing these information with all of us. whatsapp mod

    ReplyDelete
  47. Great blog. keep sharing more.

    Full-stack developers have the qualifications and experience to add market-exciting features to your product. The experts can handle the entire stack from the ground up. If you want to see a return on your investment, you must rely on such knowledge. Not everyone is equipped to handle your web project from start to finish. Learn over 30 Full Stack tools and technologies and put them to use on numerous projects. Complete a Full stack training in Pune to master these abilities and land a job.
    (https://www.iteducationcentre.com/full-stack-training-institute-in-pune.php)

    ReplyDelete
  48. Java is a programming language that can create programmes for a variety of platforms. Sun Microsystems created Java, a high-level programming language. There are several programmes and websites that will not function unless Java is installed. It is a popular choice among developers and hubs since it is dependable, quick, and secure. Java can be found anywhere.

    Expertise in both front end and back end JavaScript-based technologies. more It-education-learning Java Classes In Pune

    ReplyDelete
  49. Wow it is one of the best things i came across on the internet.
    Java Classes in Pune

    ReplyDelete
  50. I like your blog. Your interview question really helpful for me. I gain more knowledge about java from your blog. If candidate want to know more about then you search 8 Most Common Guesstimate Interview Questions & Answers [For Freshers] for more questions.

    ReplyDelete
  51. This comment has been removed by the author.

    ReplyDelete
  52. Thanks for the blog, these questions really help in interview. To Learn a Java course, join an institute for Java course, which provides Java training in Kanpur, Gorakhpur, Delhi, Noida, and many more cities in India.

    ReplyDelete
  53. Great blog post! I found your insights on the topic to be really helpful and informative. Your writing style is engaging and easy to follow, making it a pleasure to read. Thanks for sharing valuable resources Besides this if you want to learn about Python Training Course in Mohali, Allahabad, Gurgaon, and all cities in India.

    ReplyDelete
  54. that's very informative and superb blog.Keep up with your great work.
    also, check Java Course in Nagpur

    ReplyDelete