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Interview Questions and Answers for 'EPAM' - 38 question(s) found - Order By Rating

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 Q1. How can we increase the speed of SQL queries ?Database
Ans. Using -
1. Prepared Statements
2. Using Indices
3. Using whereby clause only on indexed columns

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   Like         Discuss         Correct / Improve          Asked in 1 Companies


 Q2. What is dynamic programming ?
Ans. Dynamic programming is as a problem solving approach in which problem is divided into simpler sub problems which are over lappping in nature and solved once. its results are stored into a suitable data structure and reused to solve bigger sub problems

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 Q3. Explain features of MongoDB.MongoDB
Ans. Document Oriented:
MongoDB stores the main subject in the minimal number of documents and not by breaking it up into multiple relational structures like RDBMS. For example, it stores all the information of a computer in a single document called Computer and not in distinct relational structures like CPU, RAM, Hard disk, etc.

Indexing: Without indexing, a database would have to scan every document of a collection to select those that match the query which would be inefficient. So, for efficient searching Indexing is a must and MongoDB uses it to process huge volumes of data in very less time.

Scalability: MongoDB scales horizontally using sharding (partitioning data across various servers). Data is partitioned into data chunks using the shard key, and these data chunks are evenly distributed across shards that resides across many physical servers. Also, new machines can be added to a running database.

Replication and High Availability: MongoDB increases the data availability with multiple copies of data on different servers. By providing redundancy, it protects the database from hardware failures. If one server goes down, the data can be retrieved easily from other active servers which also had the data stored on them.

Aggregation: Aggregation operations process data records and return the computed results. It is similar to the GROUPBY clause in SQL. A few aggregation expressions are sum, avg, min, max, etc

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 Q4. Difference between List and LinkedList ?Core Java
Ans. A List is an child interface of collection interface in java where as Linked list is and implementation class of List interface which has doubly linked as a underlying data structure

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   Like         Discuss         Correct / Improve     linkedlist  list vs linkedlist     Asked in 1 Companies


 Q5. What are the technologies you would like to work on ?General
Ans. Java 7 , SQL Server

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   Like         Discuss         Correct / Improve          Asked in 2 Companies


 Q6. What are the ways to break singleton pattern ?Design
Ans. If we don't have double checked locking, it can be broken easily through multi threaded access.

Through Reflection.

If multiple class loaders are loading the class.

If the class is serializable or cloneable.


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   Like         Discuss         Correct / Improve     singleton     Asked in 2 Companies      expert


 Q7. In the Following code which foo will get called.

foo(Integer i){
}

foo(String s){
}

public static void main(){
passing foo(null);
}
Core Java
Ans. ambiguity error

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 Q8. Find different combination of given String and trace the output

Core Java
Ans. private void permutation(String prefix, String sufix)
{
int ln = sufix.length();
if(ln == 0) {
System.out.println(prefix);
} else {
IntStream.range(0, ln).forEach(i->permutation(prefix sufix.charAt(i), sufix.substring(0,i) sufix.substring(i 1, ln)));
}
}

call:permutation("", "abcdef");

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   Like         Discuss         Correct / Improve     String  code  coding     Asked in 1 Companies


 Q9. Find Max from Stack in O(1) complexityAlgorithm
Ans. Create one extra field called MAX O(1)

when you an element to the stack check these two condition
1. Stack is empty, then MAX = element
2. Stack is not empty then check if the element is greater than MAX then MAX = element


when getMax fuction is called, then return MAX

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   Like         Discuss         Correct / Improve     complexity  stack  data structure     Asked in 1 Companies


Frequently asked in Genpact.
 Q10. What is object cloning ?Core Java
Ans. Its is the process of creating exact copy of an object being cloned. In Object class one native method called clone() is there which is meant for Shallow Cloning of Object. Shallow cloning means bitwise copy of an object.In case of primitive data type it will create an exact copy of primitive values as well as variables but if the object contains any reference of an object then it will not copy the referenced object rather it will create the copy of reference variable and assigned it to the old object.

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   Like         Discuss         Correct / Improve     cloning     Asked in 3 Companies      basic        frequent


 Q11. What is the use of static keyword in Java ?Core Java
Ans. static keyword is used to specify that the respective programming construct ( method , variable ) belongs to the class and not to its instance and is supposed to be shared by all instances of the class.

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   Like         Discuss         Correct / Improve     static keyword     Asked in 1 Companies      basic        frequent


 Q12. How is hashcode calculated in java ?

or

What are the rules for hashcode calculation ?
Core Java
Ans. General contract of hashCode is:

1.Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer,

2.If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.

3.It is not required that if two objects are unequal according to the equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results.

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   Like         Discuss         Correct / Improve     hashcode     Asked in 1 Companies      expert


 Q13. Given a 12-hour analog clock, compute in degree the smaller angle between the hour and minute hands
Ans. Zero Degree. Because the hour and minute hands overlap once in an hour.

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 Q14. What is a factory design pattern ?Design
Ans. Factory Design Patterns is the pattern that recommends creation of separate Factory Object for creation of other object.

So its like saying - If you want to create an object of ClassA, Talk to FactoryObject ( which is an object of FactoryClass ). FactoryObject in itself encapsulates the inputs and logic required to make the decision regarding the creation and construction of object.

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   Like         Discuss         Correct / Improve     design pattern  factory design pattern     Asked in 9 Companies


 Q15. What would you do if a customer asks you to make a change immediately that require some time for thinking and analysis ?General
Ans. [Open Ended Answer]

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 Q16. What was the most difficult task in your last job ?General
Ans. [Open Ended Answer]

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 Q17. What technical stuff you like to do in your free time ?General
Ans. [Open Ended Answer]

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   Like         Discuss         Correct / Improve          Asked in 2 Companies        frequent


Frequently asked in Cognizant ( Based on 2 feedback )
  Q18. What are Inner , Outer , Left and Right Joins in SQL ?Database
Ans. Inner join is the intersection of two tables on the condition defined by the where clause i.e will get records from both tables matched by a column.

Outer join is the union of two tables i.e will get all records from both tables and will put null in the columns where related records are not present.

Left Outer join is the left union of two tables i.e all records from the table on the left and values from the right table for related records else null for the columns from right table.

Right Outer join is the right union of two tables i.e all records from the table on the right and values from the left table for related records else null for the columns from left table.

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   Like         Discuss         Correct / Improve     sql  inner join  outer join  right join  left join     Asked in 24 Companies      basic        frequent


  Q19. 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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   Like         Discuss         Correct / Improve     exception handling     Asked in 18 Companies      basic        frequent


 Q20. When is the situation when finally section won't execute ?Core Java
Ans. If the process / app is abruptly killed or terminated.

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   Like         Discuss         Correct / Improve     exception handling  finally     Asked in 2 Companies      intermediate

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 Q21. How to make sure that only one instance is created in Singleton Pattern ?Core Java
Ans. public class SingleTon {
private SingleTon() {
if (singleTon != null) {
throw new RuntimeException("cant not create the object");
}
}
public Object clone() throws CloneNotSupportedException {
throw new CloneNotSupportedException("can not be create");
}

static private volatile SingleTon singleTon;
public static SingleTon getInstance() {
SingleTon singleTon = this.sample;
if (singleTon == null) {
synchronized (this) {
singleTon = this.singleTon;
if (singleTon == null) {
singleTon = this.singleton = new SingleTon();
}
}
}
return singleTon;
}
}

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 Q22. Difference between Static and Singleton Class ?Core Java
Ans. 1. Static class is a class which cannot be instantiated and all its members are static whereas Singleton is the class that only permit creation of single object and then the object is reused.

2. As there is no object in Static class, it cannot participate in runtime Polymorphism.

3. As Static class doesnt allow creating objects and hence it cannot be serialized.

4. Static class body is initialized eagerly at application load time whereas Singleton object can be initiated eagerly using static blocks or lazily on first need.

5. Its not recommended to use pure static class as it fails to use many OOPs concepts.

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   Like         Discuss         Correct / Improve     Static Class  Singleton  Static Class vs Singleton     Asked in 3 Companies      Intermediate        frequent


 Q23. Have you ever had any conflict with the team member (like disagreement on some design decision ) and How you reacted to it ? General
Ans. [Open Ended Answer]

This is a very sensitive question and should be dealt with caution. Just simply saying that you never had any disagreement will present you as dumb team member. Showing your self as too aggressive in such decisions will present you as a trouble maker. You should present a situation where you had an argument / disagreement but eventually you and your team mates mutually found a way out of it.

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   Like         Discuss         Correct / Improve          Asked in 20 Companies      basic


  Q24. What is coupling and Cohesion ?Design
Ans. Coupling is the degree of interdependence between software modules, a measure of how closely connected two modules are or the strength of the relationships between modules.

Cohesion refers to the degree to which the elements of a module belong together. Cohesion measures the strength of relationship between pieces of functionality within a given module.

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   Like         Discuss         Correct / Improve     coupling  cohesion     Asked in 10 Companies        frequent


 Q25. What are design situations to use Singleton and Prototype Design Pattern ?Design
Ans. Both are creational design patterns.

Singleton is used when we would like to reuse an object if object is not supposed to hold request or thread specific information. Inversely Prototype is used in situations where we would like to reuse the object information but the request / thread may require it own data to be persisted.

In short, Singleton is used in situations where we can live with single object being shared across multiple requests or threads whereas Prototype is used when we need duplicate copies of objects.

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   Like         Discuss         Correct / Improve     design pattern  singleton  prototype  creational design pattrn     Asked in 7 Companies      expert

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Very frequently asked. Among first few questions in almost all interviews. Among Top 5 frequently asked questions. Frequently asked in Indian service companies (HCL,TCS,Infosys,Capgemini etc based on multiple feedback ) and Epam Systems
  Q26. Difference between == and .equals() ?Core Java
Ans. "equals" is the method of object class which is supposed to be overridden to check object equality, whereas "==" operator evaluate to see if the object handlers on the left and right are pointing to the same object in memory.

x.equals(y) means the references x and y are holding objects that are equal. x==y means that the references x and y have same object.

Sample code:

String x = new String("str");
String y = new String("str");

System.out.println(x == y); // prints false
System.out.println(x.equals(y)); // prints true

  Sample Code for equals

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   Like         Discuss         Correct / Improve     java   string comparison   string   object class   ==    equals   object equality  operator   == vs equals   equals vs ==     Asked in 294 Companies      basic        frequent

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Frequently asked. Favorite question in Walk in Drive of many Indian service companies.
  Q27. What are the methods of Object Class ?Core Java
Ans. clone() - Creates and returns a copy of this object.

equals() - Indicates whether some other object is "equal to" this one.

finalize() - Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.

getClass() - Returns the runtime class of an object.

hashCode() - Returns a hash code value for the object.

toString() - Returns a string representation of the object.

notify(), notifyAll(), and wait() - Play a part in synchronizing the activities of independently running threads in a program.

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   Like         Discuss         Correct / Improve     java   oops   object class     Asked in 16 Companies      basic        frequent

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Very Frequently asked to fresh graduates and less experienced. Favorite question in Walk in drives. Frequently asked in Indian Services companies.
  Q28. Difference between Overloading and Overriding ?Core Java
Ans. Overloading - Similar Signature but different definition , like function overloading.

Overriding - Overriding the Definition of base class in the derived class.

  Sample Code for overloading

  Sample Code for overriding

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Frequently asked question for intermediate developers. Frequently asked in HCL Technologies and EPAM.
  Q29. What is Volatile keyword used for ?Core Java
Ans. Volatile is a declaration that a variable can be accessed by multiple threads and hence shouldnt be cached.

  Sample Code for volatile

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 Q30. Difference between Factory and Builder Design Pattern ?Design
Ans. Builder pattern is the extension of Factory pattern wherein the Builder class builds a complex object in multiple steps.

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