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Deloitte


   




Interview Questions and Answers for 'Deloitte' - 45 question(s) found - Order By Newest

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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.

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

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

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Frequently asked question in companies using Hibernate.
  Q3. What is Lazy Initialization in Hibernate ?Hibernate
Admin
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Ans. It's a feature to lazily initialize dependencies , relationship and associations from the Database. Any related references marked as @OneToMany or @ManyToMany are loaded lazily i.e when they are accessed and not when the parent is loaded.

  Sample Code for Lazy Initialization

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   Like         Discuss         Correct / Improve     hibernate   lazy loading hibernate   lazy initialization hibernate   architecture     Asked in 77 Companies      Basic        frequent

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Very frequently asked. Favorite question in Walk in Drive of many Indian service companies.
  Q4. What is the difference between ArrayList and LinkedList ?Core Java
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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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   Like         Discuss         Correct / Improve     collections   java   data structures   arraylist   linkedlist     Asked in 61 Companies      Basic        frequent

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Basic and Very Frequently asked.
  Q5. 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

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

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 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     Asked in 1 Companies      intermediate        rare

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  Q7. Difference between Vector and ArrayList ?Core Java
Anonymous
Ans. Vectors are synchronized whereas Array lists are not.

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  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.

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   Like         Discuss         Correct / Improve     java   oops   serialization   transient   java keywords     Asked in 39 Companies      intermediate        frequent

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 Q9. 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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   Like         Discuss         Correct / Improve     java   oops   immutable  immutability   immutable  immutability class   technical lead     Asked in 5 Companies      intermediate        frequent

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Advanced level question. Recently asked in few Indian service companies ( Based on 3 inputs )
 Q10. What are various types of Class loaders used by JVM ?Core Java
Admin
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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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Very Frequently asked. Usually asked along with String Class related questions.
  Q11. 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.

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 Q12. what is fail fast and Fail Safe in collections?Core Java2017-12-26 10:01:44

Ans. Iterators in java are used to iterate over the Collection objects.

Fail-Fast iterators immediately throw ConcurrentModificationException if there is any addition, removal or updation of any element.

Fail-Safe iterators don't throw any exception if a collection is structurally modified while iterating over it. This is because, they operate on the clone of the collection and not on the original collection.

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   Like         Discuss         Correct / Improve     ail fast   fail saf     Asked in 8 Companies      intermediate


 Q13. 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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 Q14. What is a binary tree ?Algorithm2017-01-19 15:38:04

Ans. Binary tree is a tree in which each node has up to two children.Tree is a data structure composed of nodes.Each tree has a root node(not necessary in graph theory). The root node has zero or more child nodes.Each child node has zero or more child nodes, and so on.The tree cannot contain cycles.

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   Like         Discuss         Correct / Improve     binary tree     Asked in 1 Companies


 Q15. Can we have multiple inheritance in java using abstract class ?Core Java2018-07-04 16:17:49

Ans. No

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 Q16. Describe structure of a Web application.architecture2018-07-04 16:18:26

Ans. WEB APP |WEB-INF - META-INF | | | META-INF.MF | lib - WEB.xml - Classes

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   Like         Discuss         Correct / Improve     web application     Asked in 3 Companies      intermediate        frequent


Frequently asked at HCL Technologies ( Based on 3 feedback )
  Q17. 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.
  Q18. What is rule regarding overriding equals and hashCode method ?Core Java
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Ans. A Class must override the hashCode method if its overriding the equals method.

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  Q19. Can we have null keys in TreeMap ?Core Java
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Ans. No, results in exception.

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


Very frequently asked. Usually followed by questions related to private constructor and synchronized access. Frequently asked in JPMorgan and TCS (Based on 2 feedback)
  Q20. Explain Singleton Design Pattern ?Design
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Ans. http://www.buggybread.com/2014/03/java-design-pattern-singleton-interview.html

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   Like         Discuss         Correct / Improve     java   design pattern   singleton   at&t   ebay  fidelity india  united healthcare india     Asked in 46 Companies      intermediate        frequent


 Q21. What is ConcurrentModificationException ?Core Java
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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     Asked in 14 Companies      intermediate


 Q22. What is ArrayIndexOutOfBoundException ?Core Java
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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.

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  Q23. Difference between jar , war and ear ?Java EE
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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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  Q24. What is Jenkins ?Jenkins
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Ans. It is a continuous integration tool written in Java.

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 Q25. 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.
 Q26. 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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Frequently asked in high end product companies. Frequently asked in Deloitte.
  Q27. 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

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  Q28. 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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   Like         Discuss         Correct / Improve     exception handling     Asked in 18 Companies      basic        frequent


 Q29. Write an algorithm / java program for Heap Sort ?Algorithm2017-01-19 15:36:18

Ans. https://www.geeksforgeeks.org/heap-sort/

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Usually asked to entry level software developers.
  Q30. 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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Frequently asked Spring interview question.
 Q31. What are the components of Spring framework ?Spring2017-02-06 11:57:01

Ans. Core: [Core, Bean, Context, Expression Language]

Web: [Web, Portlet, Servlet, etc]

Data Access [JMS, JDBC, etc]

AOP, Aspect

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 Q32. Is HttpServlet an abstract class ?Java EE2018-02-19 13:09:49

Ans. Yes

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 Q33. Create a stack of specific size using arrayList?Data Structure2018-04-04 21:33:45

Ans. public class StackUsingArrayList {
   public static void main(String[] args) {
      List list = new ArrayList();
      list.add("A");
      list.add("B");
      list.add("C");
      
      Stack stack = new Stack();

      list.forEach(a -> stack.add(a));
      System.out.println(stack);
   
   }
}

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  Q34. Write code to sort an array.Algorithm2018-07-04 16:15:16

Ans. https://www.geeksforgeeks.org/arrays-sort-in-java-with-examples/

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   Like         Discuss         Correct / Improve     array  sorting     Asked in 16 Companies      basic        frequent


  Q35. Difference between == and === ?JavaScript2018-07-04 16:16:18

Ans. == compares values === is used in scripting languages for comparing two values as well as there data tpe. like in js,php.

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   Like         Discuss         Correct / Improve     ==  ===  == vs ===     Asked in 13 Companies      basic        frequent


 Q36. 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.

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 Q37. 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.


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 Q38. If your application has multiple databases, how many changes you have to made in Hibernate? Hibernate2018-07-04 16:21:07

Ans. If you have mulitple Databases you just need to add multiple configuration files and create the corresponding SessionFactory object.

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 Q39. If SOAP is more secure than Rest, Why many applications today use Rest ?Web Service2018-07-04 16:21:38

Ans. SOAP supports only xml whereas Rest support many other formats.

Rest services are very light weight compared to SOAP.

SOAP services are code heavy as they require creation. of stubs and skeltons.

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   Like         Discuss         Correct / Improve     soap  rest  soap vs rest     Asked in 2 Companies


 Q40. What are different types of IOC containers ?Design2018-07-04 16:22:36

Ans. J2ee Web Containers and Core Containers

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