Interview Questions and Answers for 'Deloitte' | Search Interview Question

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Q11. Difference between Vector and ArrayList ?

Core Java

Ans. Vectors are synchronized whereas Array lists are not.

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Q12. What is the use of Transient Keyword ?

Core Java

Ans. It in Java is used to indicate that a field should not be serialized.

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Very Frequently asked. Usually asked along with String Class related questions.

Q13. What is an immutable class ?

Core Java

Ans. Class using which only immutable (objects that cannot be changed after initialization) objects can be created.

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Q14. what is fail fast and Fail Safe in collections?

Core Java

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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Q15. What is ConcurrentModificationException ?

Core Java

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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Usually asked to entry level software developers.

Q16. Write a program to swap two variables without using third

Core Java

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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Q17. Difference between jar , war and ear ?

Java EE

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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Q18. Write an algorithm / Java Program to show duplicates in an array of n elements?

Algorithm

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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Q19. What is a binary tree ?

Algorithm

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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Q20. Can we have multiple inheritance in java using abstract class ?

Core Java

Ans. No

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Q21. Describe structure of a Web application.

architecture

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Q22. What are the types of authentication used in Web services ?

Web Service

Ans. Encrypted User Name / Password
Encrypted Password within Cookie
Encrypted Tokens
IP
Client Certificates
Oauth

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Q23. Have you ever heard about csrf attacks ?

Security

Ans. Yes, Cross-Site Request Forgery (CSRF) is an attack that forces an end user to execute unwanted actions on a web application in which they're currently authenticated.

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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.

Q24. What is rule regarding overriding equals and hashCode method ?

Core Java

Ans. A Class must override the hashCode method if its overriding the equals method.

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Q25. Can we have null keys in TreeMap ?

Core Java

Ans. No, results in exception.

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Very frequently asked. Usually followed by questions related to private constructor and synchronized access. Frequently asked in JPMorgan and TCS (Based on 2 feedback)

Q26. Explain Singleton Design Pattern ?

Design

Ans. http://www.buggybread.com/2014/03/java-design-pattern-singleton-interview.html

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Q27. What is ArrayIndexOutOfBoundException ?

Core Java

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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Q28. What is Jenkins ?

Jenkins

Ans. It is a continuous integration tool written in Java.

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Q29. What are the disadvantages of multithreading ?

Core Java

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.

Q30. What is the use of synchronized keyword ?

Core Java

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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Q31. What is an exception and exception handling in Java ?

Core Java

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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Q32. Write an algorithm / java program for Heap Sort ?

Algorithm

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

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Frequently asked Spring interview question.

Q33. What are the components of Spring framework ?

Spring

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

Web: [Web, Portlet, Servlet, etc]

Data Access [JMS, JDBC, etc]

AOP, Aspect

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Q34. Is HttpServlet an abstract class ?

Java EE

Ans. Yes

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Q35. Create a stack of specific size using arrayList?

Data Structure

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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Q36. Write code to sort an array.

Algorithm

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

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Q37. Difference between == and === ?

JavaScript

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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Q38. What is the difference between abstraction and abstract class ?

Core Java

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

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Q39. Write code to print a Pyramid pattern ?

Core Java

Ans. public static void printTriagle(int n)
{
// outer loop to handle number of rows
// n in this case
for (int i=0; i1; j--)
{
// printing spaces
System.out.print(" ");
}

// inner loop to handle number of columns
// values changing acc. to outer loop
for (int j=0; j<=i; j )
{
// printing stars
System.out.print("* ");
}

// ending line after each row
System.out.println();
}
}

// Driver Function
public static void main(String args[])
{
int n = 5;
printTriagle(n);
}

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Q40. If your application has multiple databases, how many changes you have to made in Hibernate?

Hibernate

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

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