Core java - Interview Questions and Answers for 'Deloitte' | Search Java Interview Question - javasearch.buggybread.com
Javasearch.buggybread.com
Share

Search Interview Questions


 3304 questions in repository.
 There are more than 200 unanswered questions.
Click here and help us by providing the answer.
 Have a video suggestion.
Click Correct / Improve and please let us know.
Label / Company      Label / Company / Text

   



Deloitte


   




Core java - Interview Questions and Answers for 'Deloitte' - 24 question(s) found - Order By Newest

Advanced level question. Frequently asked in High end product companies. Frequently asked in Cognizant and Deloitte ( Based on 2 feedback )
  Q1. Why is String immutable in Java ?Core Java
Anonymous
Ans. 1. String Pool - When a string is created and if it exists in the pool, the reference of the existing string will be returned instead of creating a new object. If string is not immutable, changing the string with one reference will lead to the wrong value for the other references.

Example -

String str1 = "String1";
String str2 = "String1"; // It doesn't create a new String and rather reuses the string literal from pool

// Now both str1 and str2 pointing to same string object in pool, changing str1 will change it for str2 too

2. To Cache its Hashcode - If string is not immutable, One can change its hashcode and hence it's not fit to be cached.

3. Security - String is widely used as parameter for many java classes, e.g. network connection, opening files, etc. Making it mutable might possess threats due to interception by the other code segment.

 Help us improve. Please let us know the company, where you were asked this question :   


   Like         Discuss         Correct / Improve     java   oops   string   string class   immutable  immutability   advanced     Asked in 37 Companies      expert        frequent

Try 4 Question(s) Test


Very frequently asked in different variations. Frequently asked in Deloitte ( 2 feedback ) , HCL Tech ( 3 feedback ) and Coginizant (CTS)
  Q2. Explain the scenerios to choose between String , StringBuilder and StringBuffer ?

or

What is the difference between String , StringBuilder and StringBuffer ?
Core Java
Anonymous
Ans. If the Object value will not change, use String Class because a String object is immutable.

If the Object value can change and will only be modified from a single thread, use StringBuilder because StringBuilder is unsynchronized(means faster).

If the Object value may change, and can be modified by multiple threads, use a StringBuffer because StringBuffer is thread safe(synchronized).

  Sample Code for String

  Sample Code for StringBuffer

  Sample Code for StringBuilder

 Help us improve. Please let us know the company, where you were asked this question :   


   Like         Discuss         Correct / Improve     java   string class   string   stringbuilder   stringbuffer     Asked in 27 Companies      basic        frequent

Try 3 Question(s) Test


Very frequently asked. Favorite question in Walk in Drive of many Indian service companies.
  Q3. What is the difference between ArrayList and LinkedList ?Core Java
admin
info@buggybread.com
Ans. Underlying data structure for ArrayList is Array whereas LinkedList is the linked list and hence have following differences -

1. ArrayList needs continuous memory locations and hence need to be moved to a bigger space if new elements are to be added to a filled array which is not required for LinkedList.

2. Removal and Insertion at specific place in ArrayList requires moving all elements and hence leads to O(n) insertions and removal whereas its constant O(1) for LinkedList.

3. Random access using index in ArrayList is faster than LinkedList which requires traversing the complete list through references.

4. Though Linear Search takes Similar Time for both, Binary Search using LinkedList requires creating new Model called Binary Search Tree which is slower but offers constant time insertion and deletion.

5. For a set of integers you want to sort using quicksort, it's probably faster to use an array; for a set of large structures you want to sort using selection sort, a linked list will be faster.

  Sample Code for ArrayList

  Sample Code for LinkedList

 Help us improve. Please let us know the company, where you were asked this question :   


   Like         Discuss         Correct / Improve     collections   java   data structures   arraylist   linkedlist     Asked in 61 Companies      Basic        frequent

Try 1 Question(s) Test


Basic and Very Frequently asked.
  Q4. What is Polymorphism in Java ?Core Java2016-11-06 09:10:54

Ans. Polymorphism means the condition of occurring in several different forms.

Polymorphism in Java is achieved in two manners

1. Static polymorphism is the polymorphic resolution identified at compile time and is achieved through function overloading whereas

2. Dynamic polymorphism is the polymorphic resolution identified at runtime and is achieved through method overriding.

  Sample Code for overloading

  Sample Code for overriding

 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve     polymorphism  object oriented programming (oops)  oops concepts  oops concepts     Asked in 107 Companies      Basic        frequent

Try 2 Question(s) Test


 Q5. Can we serialize static variables ?Core Java
Anonymous
Ans. No. Only Object and its members are serialized. Static variables are shared variables and doesn't correspond to a specific object.

 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve     serialization   java   oops   static   static variables     Asked in 1 Companies      intermediate        rare

Try 2 Question(s) Test


  Q6. Difference between Vector and ArrayList ?Core Java
Anonymous
Ans. Vectors are synchronized whereas Array lists are not.

 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve     java   basic interview question   vector   arraylist   collections   synchronization     Asked in 34 Companies      basic        frequent


Advanced level question. Recently asked in few Indian service companies ( Based on 3 inputs )
 Q7. What are various types of Class loaders used by JVM ?Core Java
Admin
info@buggybread.com
Ans. Bootstrap - Loads JDK internal classes, java.* packages.

Extensions - Loads jar files from JDK extensions directory - usually lib/ext directory of the JRE

System - Loads classes from system classpath.

 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve     java   jvm   memory management   class loaders   bootstrap   extensions   system  classloaders   advanced   technical lead   technical architect     Asked in 7 Companies


  Q8. What is the use of Transient Keyword ?Core Java
Anonymous
Ans. It in Java is used to indicate that a field should not be serialized.

 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve     java   oops   serialization   transient   java keywords     Asked in 38 Companies      intermediate        frequent

Try 2 Question(s) Test


Very Frequently asked. Usually asked along with String Class related questions.
  Q9. What is an immutable class ?Core Java
Anonymous
Ans. Class using which only immutable (objects that cannot be changed after initialization) objects can be created.

 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve     java   oops   immutable  immutability   immutable  immutability class   string class   basic interview question     Asked in 17 Companies      Basic        frequent

Try 2 Question(s) Test


 Q10. How to implement an immutable class ?Core Java
Anonymous
Ans. We can make a class immutable by

1. Making all methods and variables as private.

2. Setting variables within constructor.

Public Class ImmutableClass{

private int member;
ImmutableClass(int var){
member=var;
}
}

and then we can initialize the object of the class as

ImmutableClass immutableObject = new ImmutableClass(5);

Now all members being private , you cant change the state of the object.

 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve     java   oops   immutable  immutability   immutable  immutability class   technical lead     Asked in 4 Companies      intermediate        frequent

Try 2 Question(s) Test


 Q11. Can we have multiple inheritance in java using abstract class ?Core Java2018-07-04 16:17:49

Ans. No

 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve     abstract class   multiple inheritance  object oriented programming (oops)  oops concepts     Asked in 1 Companies


Frequently asked at HCL Technologies ( Based on 3 feedback )
  Q12. Difference between Checked and Unchecked exceptions ?Core Java
Anonymous
Ans. Checked exceptions are the exceptions for which compiler throws an errors if they are not checked whereas unchecked exceptions are caught during run time only and hence can't be checked.

 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve     java   exceptions   checked exceptions   unchecked exceptions   exception handling   basic interview question     Asked in 37 Companies      basic        frequent

Try 1 Question(s) Test


Very Frequently asked. Favorite question in walkins and telephonic interviews. Usually among first few questions. Asked in different variants. Must know for intermediate and expert professionals.Among Top 10 frequently asked questions.
  Q13. What is rule regarding overriding equals and hashCode method ?Core Java
Admin
info@buggybread.com
Ans. A Class must override the hashCode method if its overriding the equals method.

 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve     java   collections   hashcode  hash code   equals   collections     Asked in 44 Companies      intermediate        frequent

Try 1 Question(s) Test


  Q14. Can we have null keys in TreeMap ?Core Java
Admin
info@buggybread.com
Ans. No, results in exception.

 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve     java   collections   treemap     Asked in 6 Companies      Basic        frequent


 Q15. What is ConcurrentModificationException ?Core Java
Admin
info@buggybread.com
Ans. This is the exception that is thrown when we try to modify the non concurrent collection class while iterating through it.

 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve     java   collections   concurrentmodificationexception   exception  concurrency     Asked in 14 Companies      intermediate


 Q16. What is ArrayIndexOutOfBoundException ?Core Java
Admin
info@buggybread.com
Ans. Exception thrown by the application is we try to access an element using an index which is not within the range of array i.e lower than 0 or greater than the size of the array.

 Help us improve. Please let us know the company, where you were asked this question :   


   Like         Discuss         Correct / Improve     java   exceptions   arrayindexoutofboundexception     Asked in 1 Companies


 Q17. What are the disadvantages of multithreading ?Core Java2016-10-11 08:47:41

Ans. 1. Switching Overheads - Even though multi threading aims at improving performance by reducing the wait time and hence improving overall throughput, there is a cost of switching resources between threads and sometime this cost can surpass the benefits if there isnt much wait for IO or external communication.

2. Debugging is hard with multi threaded code.

3. Deadlock - Execution of multi threaded code many a times lead to deadlock due to shared resources.

 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve     multithreading  threads     Asked in 4 Companies


Very frequently asked.
 Q18. What is the use of synchronized keyword ?Core Java2016-11-04 08:15:53

Ans. Synchronize is used to achieve mutual exclusion i.e at one time, the segment of the code, method that has been declared synchronized should be executed by single thread only and hence the lock needs to be retrieved before executing the segment and then released.

 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve     threads  multithreading  synchronized     Asked in 5 Companies      basic        frequent


Frequently asked in high end product companies. Frequently asked in Deloitte.
  Q19. How is Hashmap internally implemented in Java ?Core Java2016-12-06 08:49:37

Ans. https://www.quora.com/How-is-Hashmap-in-Java-implemented-internally-What-are-the-pros-and-cons-to-use-it-What-are-the-complexities-it-provides-for-insert-delete-and-lookup/answer/Anshudeep-Bajpai?srid=iwnK

 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve     hashmap  collections  hashmap internal implementation     Asked in 18 Companies      expert        frequent


  Q20. What is an exception and exception handling in Java ?Core Java2017-01-09 13:01:40

Ans. An Exception in java is the occurrence during computation that is anomalous and is not expected.

Exception handling is the mechanism which is used to handle such situations.


 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve     exception handling     Asked in 18 Companies      basic        frequent


Usually asked to entry level software developers.
  Q21. Write a program to swap two variables without using thirdCore Java2017-01-19 15:38:34

Ans. public static void main(String[] args) {
   int num1 = 1;   
   int num2 = 2;
   num1 = num1^num2;
   num2 = num1^num2;
   num1 = num1^num2;
   System.out.print("num1 = " + num1 +", num2 = "+num2);
}

 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve     code  coding     Asked in 37 Companies      basic        frequent


 Q22. What is the difference between abstraction and abstract class ?Core Java2018-07-04 16:17:01

Ans. Abstract class is one of the facility for achieving abstraction in Java.

 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve          Asked in 1 Companies


 Q23. Write code to print a Pyramid pattern ?Core Java2018-07-04 16:19:52

 This question was recently asked at 'Deloitte'.This question is still unanswered. Can you please provide an answer.


 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve          Asked in 1 Companies


 Q24. How to sort objects based on one of the field ?Core Java2018-07-04 16:23:09

Ans. Using comparable and comparator and sorted collections like TreeSet or TreeMap.

or

use stream api from java 8 onwards which internally refers to comparable and comparator through lambda expressions

 Help us improve. Please let us know the company, where you were asked this question :   

   Like         Discuss         Correct / Improve     sort  sorting  comprator  comparable  treeset  treemap  sorting collections     Asked in 1 Companies      Basic        frequent




Subscribe to Java News and Posts. Get latest updates and posts on Java from Buggybread.com
Enter your email address:
Delivered by FeedBurner



comments powered by Disqus
 

Help us and Others Improve. Please let us know the questions asked in any of your previous interview.

Any input from you will be highly appreciated and It will unlock the application for 10 more requests.

Company Name:
Questions Asked:
         

X Close this

Deloitte: When Negotiating salary, better expect 20-30% from ... Anonymous

Deloitte: Be Aware of their Leave Policy. Though ... Anonymous