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

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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
  Q1. 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 to fresh graduates and less experienced developers. Among the first few questions in many interviews.
  Q2. What are the difference between composition and inheritance in Java?Core Java
Ans. Composition - has-a relationship between objects.
Inheritance - is-a relationship between classes.

Composition - Composing object holds a reference to composed objects and hence relationship is loosely bound.
Inheritance - Derived object carries the base class definition in itself and hence its tightly bound.

Composition - Used in Dependency Injection
Inheritance - Used in Runtime Polymorphism

Composition - Single class objects can be composed within multiple classes.
Inheritance - Single class can only inherit 1 Class.

Composition - Its the relationship between objects.
Inheritance - Its the relationship between classes.

  Sample Code for inheritance

  Sample Code for composition

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Very frequently asked. Favorite question in Walk in Drive of many Indian service companies. Frequently asked in HCL Technologies, TCS and Accenture.
  Q3. What is the difference between final, finally and finalize() ?Core Java
Ans. final - constant variable, objects cannot be de-referenced, restricting method overriding, restricting class sub classing.

finally - handles exception. The finally block is optional and provides a mechanism to clean up regardless of what happens within the try block. Use the finally block to close files or to release other system resources like database connections, statements etc.

finalize() - method helps in garbage collection. A method that is invoked before an object is discarded by the garbage collector, allowing it to clean up its state.

  Sample Code for final

  Sample Code for finally

  Sample Code for finalize

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   Like         Discuss         Correct / Improve     java   oops   final   finally   finalize   final vs finally vs finalize     Asked in 61 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.
  Q4. 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 in Cognizant ( Based on 2 feedback )
  Q5. 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


Frequently asked. Favorite question in Walk in Drive of many Indian service companies.
  Q6. 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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 Q7. 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


Very frequently asked in companies using SOA.
  Q8. What are RESTful Web Services ?Rest
Ans. REST or Representational State Transfer is a flexible architecture style for creating web services that recommends the following guidelines -

1. http for client server communication,
2. XML / JSON as formatiing language ,
3. Simple URI as address for the services and,
4. stateless communication.

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   Like         Discuss         Correct / Improve     java   web services   rest   java   j2ee  architecture     Asked in 14 Companies      intermediate        frequent


Frequently asked question for intermediate developers. Frequently asked in HCL Technologies and EPAM.
  Q9. 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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 Q10. What is a stream and what are the types of Streams and classes of the Streams?Core Java
Ans. A Stream is an abstraction that either produces or consumes information. There are two types of Streams :

Byte Streams: Provide a convenient means for handling input and output of bytes.

Character Streams: Provide a convenient means for handling input & output of characters.

Byte Streams classes: Are defined by using two abstract classes, namely InputStream and OutputStream.

Character Streams classes: Are defined by using two abstract classes, namely Reader and Writer.

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   Like         Discuss         Correct / Improve     java   file io   streams   byte stream   character stream  file handling     Asked in 3 Companies


 Q11. 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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  Q12. What is reflection ?
Ans. It is the process of examining / modifying the behaviour of an object at runtime.

  Sample Code for reflection

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Very Frequently asked.
 Q13. Explain throw, throws , try and catch in Java ?Core Java
Ans. throw is used to re throw an exception.throws is used to declare that the method throws the respective exceptions.try block is used to identify if the respective block has thrown any exception.catch is used to catch the exception that has been thrown by the respective try block.

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   Like         Discuss         Correct / Improve     java   exception handling   throw   throws   try   catch     Asked in 5 Companies      basic        frequent


  Q14. 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


 Q15. Which java frameworks have you used ?General
Ans. I have primarily worked on Web applications and hence worked on Struts , Spring , Hibernate, JSF ( Java Server Faces ) , Velocity etc.

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   Like         Discuss         Correct / Improve     elsevier   frameworks   java frameworks   general question     Asked in 3 Companies      basic        frequent


 Q16. 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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 Q17. 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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 Q18. 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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 Q19. 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


 Q20. 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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Very frequently asked. Usually followed by questions related to private constructor and synchronized access. Frequently asked in JPMorgan and TCS (Based on 2 feedback)
  Q21. Explain Singleton Design Pattern ?Design
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


 Q22. 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


 Q23. 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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   Like         Discuss         Correct / Improve     singleton  design pattern     Asked in 2 Companies


  Q24. 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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 Q25. What technical stuff you like to do in your free time ?General
Ans. [Open Ended Answer]

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 Q26. What was the most difficult task in your last job ?General
Ans. [Open Ended Answer]

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 Q27. 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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 Q28. 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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 Q29. 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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 Q30. 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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