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Interview Questions and Answers - Order By Newest | ||||
Very frequently asked in phone and walk in interviews. | ||||
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Ans. An interface without any method declaration is called as marker interface. there are 3 in-built interfaces in JVM i.e. serializable, clonable, remote | ||||
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Like Discuss Correct / Improve  java   oops   interfaces   marker interface   serializable   clonable Asked in 21 Companies intermediate   frequent | ||||
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Very frequently asked. Usually difference between String,StringBuffer and StringBuilder is asked in different variations. | ||||
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Ans. StringBuffer is synchronized whereas StringBuilder is not. | ||||
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Like Discuss Correct / Improve  java   string   stringbuffer   string class   stringbuilder   synchronized   basic interview question   infosys technologies Asked in 17 Companies basic   frequent | ||||
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Ans. It is the process of examining / modifying the behaviour of an object at runtime. | ||||
Sample Code for reflection | ||||
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Like Discuss Correct / Improve  java   reflection   reflection api   ebay   mindtree Asked in 29 Companies basic   frequent | ||||
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Ans. It should be followed by either catch or finally block. | ||||
Sample Code for Retry in case of exception | ||||
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Like Discuss Correct / Improve  java   exceptions   exception handling   try   catch   finally  Oracle OCA Test Asked in 3 Companies basic   frequent | ||||
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Frequently asked in CTS ( Based on 2 feedback ) | ||||
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Ans. Comparable interface is used for single sequence sorting i.e.sorting the objects based on single data member where as comparator interface is used to sort the object based on multiple data members. | ||||
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Like Discuss Correct / Improve  java   java.util   comparable   comparator   collections Asked in 23 Companies basic   frequent | ||||
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Ans. Collections are re-sizable in nature. We can increase or decrease the size as per recruitment. Collections can hold both homogeneous and heterogeneous data's. Every collection follows some standard data structures. Collection provides many useful built in methods for traversing,sorting and search. | ||||
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Like Discuss Correct / Improve  java   collections   collections classes   advantages of collections over arrays   collections vs arrays   basic interview question Asked in 6 Companies basic   frequent | ||||
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Ans. Abstraction is provided in Java by following ways - Coding to the ( Interfaces / Abstract Classes ) or contracts By Encapsulating details within classes and exposing the minimal Door ( few public methods ) | ||||
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Like Discuss Correct / Improve  java   oops concepts   abstraction   interfaces   abstract class   encapsulation  object oriented programming (oops)  oops concepts Asked in 3 Companies basic   frequent | ||||
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Ans. DEBUG ERROR ALL WARN INFO FATAL OFF TRACE TRACE_INT WARN | ||||
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Like Discuss Correct / Improve  java   log4j   log4j level   logging   error logging Asked in 10 Companies | ||||
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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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Like Discuss Correct / Improve  java   j2ee   jar   web development   war   ear   build management   release management Asked in 12 Companies basic   frequent | ||||
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Ans. Java only provides pass by value. | ||||
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Like Discuss Correct / Improve  ebay   pass by value   pass by reference   method call   methods   functions   function call Asked in 10 Companies basic   frequent | ||||
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Ans. When a Table Join itself , it's a Self Join. For example - we like to know the pair of department names where first dept has lesser employees than the later. Select D1.name , D2.name from Dept D1, Dept D2 where D1.employee_count < D2.employee_count | ||||
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Like Discuss Correct / Improve  sql  joins  self join  self-join  Pair of employee names with first having lesser salary than later  Pair of department names where first dept has lesser employees than the later Asked in 26 Companies basic   frequent | ||||
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Ans. https://en.wikipedia.org/wiki/Database_normalization | ||||
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Like Discuss Correct / Improve  normalization  database Asked in 35 Companies intermediate   frequent | ||||
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Ans. Authentication is the process of verifying the identity and credentials of the user to authenticate him into the system. whereas Authorization is the process by which access to a segment , method or resource is determined. Authorization is usually a step next to authentication. | ||||
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Like Discuss Correct / Improve  authentication  authorization  authentication vs authorization Asked in 9 Companies basic   frequent | ||||
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Ans. Amazon Simple Storage Service or S3 is object storage with a simple web service interface to store and retrieve any amount of data from anywhere on the web. | ||||
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Like Discuss Correct / Improve  aws  amazon s3  aws s3  aws storage  amazon cloud storage  amazon s3 Asked in 12 Companies | ||||
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Ans. By using synchronized static method or synchronized block | ||||
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Like Discuss Correct / Improve  threads  synchronization  static methods Asked in 2 Companies intermediate | ||||
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Ans. Abstraction is a process of hiding the implementation details and describing only the functionality to the user. | ||||
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Like Discuss Correct / Improve  bstraction  oops concepts  oops principle Asked in 22 Companies | ||||
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Ans. Encrypted User Name / Password Encrypted Password within Cookie Encrypted Tokens IP Client Certificates Oauth | ||||
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Like Discuss Correct / Improve  authentication  security  web service Asked in 12 Companies basic   frequent | ||||
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Ans. A cookie is a small piece of text stored on a user's computer by the browser for a specific domain. Commonly used for authentication, storing site preferences, and server session identification. | ||||
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Like Discuss Correct / Improve  cookie   javascript   web application   session management   browser   j2ee Asked in 16 Companies basic   frequent | ||||
Frequently asked. | ||||
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Ans. Iterator is an interface that provides methods to iterate over any Collection. | ||||
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Like Discuss Correct / Improve  java   collections   iterator Asked in 11 Companies basic   frequent | ||||
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Ans. Transient variables are variable that cannot be serialized. | ||||
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Like Discuss Correct / Improve  java   serialization   transient Asked in 15 Companies intermediate   rare | ||||
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Ans. Hashcode is used for bucketing in Hash implementations like HashMap, HashTable, HashSet etc. | ||||
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Like Discuss Correct / Improve  java   string   hashcode   hash code   string comparison  hashtable Asked in 17 Companies basic   frequent | ||||
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Ans. 1. EHCache ( Easy Hibernate ) 2. OSCache ( Open Symphony ) 3. Swarm Cache ( JBoss ) 4. Tree Cache ( JBoss ) | ||||
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Like Discuss Correct / Improve  hibernate   orm   hibernate cache   technical lead Asked in 7 Companies | ||||
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Ans. Criteria is a simplified API for retrieving entities by composing Criterion objects. For example - session.createCriteria(Employee.class).add( Restrictions.like("name", "A%") ).list(); will return all employee objects having name starting with A. | ||||
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Like Discuss Correct / Improve  hibernate   hibernate criteria Asked in 7 Companies Basic   Frequent | ||||
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Ans. We are using Agile methodology. I attend daily stand up where the development leads takes the status of assigned stories, achievements, any bottlenecks or challenges. We follow iteration of 2 weeks. | ||||
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Like Discuss Correct / Improve  sdlc   agile methodology   software system analyst   software developer interview   development lead   project lead interview Asked in 14 Companies   frequent | ||||
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Ans. HashMap | ||||
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Like Discuss Correct / Improve  java   collections   map  hashtable Asked in 2 Companies basic   frequent | ||||
Must know at all levels. Among Top 10 frequently asked questions in Java. Very frequently asked to fresh graduates or less experienced professionals. | ||||
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Ans. Its a facility for code reuse and independent extension wherein a derived class inherits the properties of parent class. | ||||
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Like Discuss Correct / Improve  inheritance  object oriented programming (oops)  oops concepts  oops concepts  java concepts  code reuse  code re-use   classes  derived classes Asked in 14 Companies basic   frequent | ||||
Very frequently asked to fresh graduates. Frequently asked in NSEiT and Accenture India | ||||
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Ans. public class Main { public static void main(String args[]) { int number = 2; int count = 0; long sum = 0; int givenNumber = 1000; while (count < givenNumber) { if (isPrimeNumber(number)) { sum = number; count; } number; } System.out.println(sum); } private static boolean isPrimeNumber(int number) { for (int i = 2; i <= number / 2; i) { if (number % i == 0) { return false; } } return true; } } | ||||
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Like Discuss Correct / Improve  generate prime numbers  code  coding Asked in 5 Companies basic   frequent | ||||
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Ans. Enums in Java are used to declare predefined objects and then reuse them. they offer many benefits 1. Enum instance are type safe and thread safe. 2. Enum instances are singleton and hence reused. 3. If we use Enums with Switch , It makes sure that the passed argument is either of its instance and hence provides a safeguard. 4. If we use Enum with Sorted Collections we can sort the elements with a predefined priorities ( as per constant declaration in enum ) 5. We can use Enum as a Factory by defining its constructor. 6. We can store related constant data within enum. For example - If we know the values for the map upfront, we can alternatively use an enum. | ||||
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Ans. JDBC is a standard Java Api for Database communication whereas Hibernate is an ORM framework that uses JDBC to connect with Database. Hibernate is another layer of object table mapping over JDBC that provide a database independent, object oriented and an efficient way of database communication. | ||||
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Like Discuss Correct / Improve  JDBC  Hibernate  JDBC vs Hibernate Asked in 3 Companies | ||||
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Ans. DELETE FROM TABLE WHERE ROW_NUM NOT IN ( SELECT MAX(ROW_ID) FROM TABLE GROUP BY DUPLICATE_FIELD ) | ||||
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Like Discuss Correct / Improve   Asked in 3 Companies | ||||