Answers to “15 Must Know Java Interview Questions After 2 Years of Experience”

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• Thanks for putting this up. There had been requests for the answers. Will link to this post from the questions post.
  Thanks once again.

  • The only suggestion I can give is regarding "equals and == difference". equals doesn't assign value. It is intended to check logical equality and == checks if both references point to same object.

    • Thank you for the correction.
      I forgot about a.equals(b).

• ... sweet, was going to look them up in free moment :-)

• final - This doesn't just declare a constant. Can also be used on a class to declare that it cannot be subclassed.

  • Let's clarify about the 'final' keyword.
    Instead of thinking of it as a way to declare a constant, think of it as a fixed declaration that cannot be changed.
    In the case of a class member, it makes it a constant.
    In a case of a class, one can't make a subclass of it.
    In case of a method, it means that even if you do make a subclass, one won't be able to override that specific method.

    There are various reasons to use the 'final' keyword - creating constants, security, making classes immutable.

• #10: No, only redirect does a redirect.

• #13: Both WAR and JAR files contain arbitrary files. A WAR is expected to adhere to specific layout guidelines.

  • A war file does not necessarily contain jsp pages (think web service)!

    the equals method returns whatever is returned by the overridden equals method of the implemented class, i.e. if the equals method body checks for equivalence of important properties of the class, then it compares logical equivalence, however, the equals method can arbitrarily return true or false, depending on the implementation.

• Hi,

  Thanks for these interview questions. I would also like to share my favorite interview questions :

  Why String is immutable in Java
  Difference between HashMap and HashTable? Can we make hashmap synchronized

  Thanks
  Javin

• well,
  I would never hire anyone that after 2 years of java is only able to give such incomplete answers.
  We usually do not hire not even entry level programmers with such low level of java knowledge.
  First this is not core java, core java has nothing to do with servlets, struts (:)) btw is Struts still a cool technology...i remeber I have used it in 2001 not now :) ...No need to mention incomplete answers about final for instance...or mixing some completely random SQL in the same java sheet ...can't see any reason...

  As a conclusion, these are good questions for an intern that wants to do some white box QA that might involve a 10-15% of java, at maximum.

  • Well... could you please then reply with the acceptable solutions to the questions posted.
    Or is it just a waste of your time because it's only 15% java?

    • that's true, you only tried to respond to another post ...
      again: those are ok, but for extremely newbie devs mixed with 'deprecated' technologies like Struts, that's all.
      So i would first change the title :).

• I have written a blog post about Top 20 Core Java Interview questions asked in Investment Bank
  ,you may find it interesting.

  • Great questions.

• Check out JavaIQ.net - it has huge collection of java interview questions.

• Hi

  Plz tell me operater overloading is not used in java.

  • No, operator overloading is not used in java, we use method overloading here

    Beena kaparwan

    • why not use operater overloading

    • operator overloading internally supported by java ....jvm internally performs that implementation......e.g +,*.........bt operator overloading is nt supported for programmers just like addresses nt supported in java.......

  • because c++ has proven by its record that its very difficult to maintain and ambuguity for the comiler....so operator overloading in not supported in java...

  • no ,operater overloading use in java

    • there is a one mechanism in java to support overloading . + operator which provides overloading in two cases
      - we can use it for addition.
      - for concatnation the two strings.

      • there is also another e.g of operator overloading i.e.......* for multiplication and importing classes from package

    • Hi Sandy,

      Operator overloading is avalable in java.In java + operator perform the operator
      overloading. But abort the + operator the remaining all operators does not support the operator overloading.

      Basha

  • Operator overloading mean , a operator can perform the many action.

    In java abort + operator , the remaining all oprators does not support the operator overloading. This + operator perform the addition on numerics and it perform concatination operation on strings.

    for example :

    System.out.println(2+3+4); o/p: 9
    System.out.println(2+3+"ranjam"); o/p: 5ranjam

    Basha