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Interview Questions and Answers for 'Deloitte' - 21 question(s) found - Order By Newest

Advanced level question. Frequently asked in High end product companies. Frequently asked in Cognizant ( Based on 2 feedbacks )
  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.

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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

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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

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  Q4. Difference between Vector and ArrayList ?Core Java
Anonymous
Ans. Vectors are synchronized whereas Array lists are not.

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Advanced level question. Recently asked in few Indian service companies ( Based on 3 inputs )
 Q5. 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.

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   Like      Discuss      Correct / Improve     java   jvm   memory management   class loaders   bootstrap   extensions   system  classloaders   advanced   technical lead   technical architect     Deloitte  Mindtree  Accenture  Synechron  IBM


 Q6. 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.

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   Like      Discuss      Correct / Improve     serialization   java   oops   static   static variables     Deloitte      intermediate        rare

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 Q7. 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.

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 Q8. Write an algorithm / Java Program to show duplicates in an array of n elements?Algorithm2017-01-19 15:37:26

Ans. int duplicateArray[] = { 1, 2, 2, 3, 4, 5, 6, 8, 9}
Set unique = new HashSet();
for (int i = 0; i < duplicateArray.length; i) {
if (unique.contains(duplicateArray[i])) {
System.out.println(duplicateArray[i]);
} else {
unique.add(duplicateArray[i]);
}
}

Complexity O(n) = nHashSet contains and add has O(n) = 1

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   Like      Discuss      Correct / Improve     coding  code     Deloitte


Frequently asked at HCL Technologies ( Based on 3 feedback )
  Q9. 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.

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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.
  Q10. 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.

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  Q11. Can we have null keys in TreeMap ?Core Java
Admin
info@buggybread.com
Ans. No, results in exception.

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 Q12. 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.

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   Like      Discuss      Correct / Improve     java   collections   concurrentmodificationexception   exception  concurrency     Calypso Technology  Deloitte  IRIS Software      intermediate


  Q13. Difference between jar , war and ear ?Java EE
Admin
info@buggybread.com
Ans. Jar is Java Archieve i.e compressed Class or Class / Java files.

War comprises of compressed Servlet class files,JSP FIles,supporting files, GIF and HTML files.

Ear comprise of compressed Java and web module files ( was files ).

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 Q14. What is Jenkins ?Jenkins
Admin
info@buggybread.com
Ans. It is a continuous integration tool written in Java.

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 Q15. 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.

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Very frequently asked.
 Q16. 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.

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  Q17. 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.


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 Q18. Write an algorithm / java program for Heap Sort ?Algorithm2017-01-19 15:36:18

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


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   Like      Discuss      Correct / Improve     sorting  heap sort     Deloitte        frequent


 Q19. What is a binary tree ?Algorithm2017-01-19 15:38:04

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


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   Like      Discuss      Correct / Improve     binary tree     Deloitte



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Usually asked to entry level software developers.
  Q20. 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);
}

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 Q21. What are the components of Spring framework ?Spring2017-02-06 11:57:01

 This question was recently asked at 'Deloitte,NZone,L&T Infotech,Ocean Consulting'.This question is still unanswered. Can you please provide an answer.


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