Core Java - Interview Questions and Answers for 'Frequent' | Search Interview Question

Interview Questions and Answers - Order By Newest

Frequently asked to Fresh graduates.

Q211. Write a program to implement Binary search ?

Core Java

Ans. http://algs4.cs.princeton.edu/11model/BinarySearch.java.html

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve binary search search Asked in 5 Companies basic frequent}

Try 1 Question(s) Test

Q212. Which data structure would you recommend for ordered and sorted data?

Core Java

Ans. TreeSet and TreeMap are used for maintaining sorted elements.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve ordered collections sorted collections Asked in 1 Companies basic frequent}

Q213. What is a Database Procedure ?

Database

Ans. Stored procedures are a batch of SQL statements along with programming constructs ( if else, loops etc ) and stored as a single program that can be called by different clients and hence reused.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve database stored procedure Asked in 2 Companies basic frequent}

Very Frequently asked to fresh graduates and less experienced.

Q214. What are the principle concepts of Object Oriented Programming ?

Core Java

Ans. Abstraction Polymorphism Inheritance Encapsulation

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve oops oops concepts Asked in 1 Companies basic frequent}

Q215. What is an IP address ?

Java EE

Ans. An Internet Protocol address is a numerical label assigned to each device participating in a computer network.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve ip address Asked in 2 Companies basic frequent}

All these acronyms JDK,JRE,JVM etc are very frequently asked.

Q216. Difference between JDK and JRE ?

Core Java

Ans. JRE or Java Runtime Environment is the Java Virtual Machine on which class files are executed. It includes borwser plugins that facilitates execution of class files in browsers.

JDK or Java Development Kit includes JRE , compiler and development tools.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve JDK JRE JDK vs JRE Difference between Asked in 4 Companies basic frequent}

Q217. What is CRUD ?

Database

Ans. CRUD stands for "Create, read, update and delete" are the basic functions of persistence.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve CRUD Persistence Database Database Operations Asked in 3 Companies Basic frequent}

Q218. What is DTO ?

Ans. DTO is Data Transfer Object i.e Pojo which is supposed to move between different layers of software architecture for transferring information. Example could be the object passed from client in case of web service call or the object passed to Persister for Database Persistence.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve DTO Data Transfer Object basic frequent}

Q219. What is DAO ?

Ans. DAO is Data Access Object which is used within Persistence Layer to make Database Transaction. For example , the class holding the Database connection and CRUD methods.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve DAO Data Access Object basic frequent}

Frequently asked for Lead and Architect positions. Recently asked in many US companies.

Q220. What are Anti Patterns ?

Design

Ans. Anti-pattern is simply the creation of a pattern in your coding that negatively affects your code i.e the Negatives surpasses the positives.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve anti patterns design patterns Asked in 9 Companies frequent}

Q221. What is a static variable in Java ?

Core Java

Ans. It is a class level variable that is shared among the objects of that class.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve static static variables class level variables Asked in 1 Companies basic frequent}

Try 1 Question(s) Test

Frequently asked question in companies using Rest Web services.

Q222. Different between POST and PUT in Rest

Rest

Ans. PUT requests are only meant to place the object as it is on server. For example - You want a file to be uploaded and then placed in a particular folder or you want an Employee object to be persisted in the table.

POST requests are also meant to transfer information from client to server but that information once received at the server is evaluated , modified or refactored before persisting.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Put vs Post Rest Asked in 5 Companies frequent}

Q223. Should a DB Insert Request be a POST or PUT request in Rest

Rest

Ans. It depends on whether the request object is persisted as it is

or

its first dismantled, modified or refactored and then inserted into DB.

In first case, it should be a PUT request whereas in second case it should be a POST Request.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Put vs Post Rest Asked in 2 Companies intermediate frequent}

Q224. What are the different ways in which information can be sent to server in web service call ?

Web Service

Ans. 1. As Request Param
2. As Path Param
3. Part of Payload / Body in case of PUT and POST Request

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve web service rest basic frequent}

Q225. Can we access private members of the parent class ? i.e Are private members of the class visible in the derived class ?

Core Java

Ans. No, If both Parent and Derived are outer classes.

public class Vehicle {
private static String manufacturingDate = "2016";
}

public class Car extends Vehicle{
public static void main(String args[]){
System.out.println(manufacturingDate); // error - The field Vehicle.manufacturingDate is not visible
}
}

Yes, If derived is the inner class of Parent.

public class Vehicle {
private static String manufacturingDate = "2016";
static public class Car extends Vehicle{
public static void main(String args[]){
System.out.println(manufacturingDate); // no problem
}
}
}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve private members private methods private variables inheritance object oriented programming (oops) oops concepts members visibility inner classes nexted classes basic frequent}

Q226. Difference between multiple and multi level inheritance ?

Core Java

Ans. Multiple Inheritance refers to the concept of a class inheriting multiple classes. Example - Class C extends Class A ,Class B. This is not allowed in Java.

Multilevel Inheritance refers to the concept of Inheritance in a chain. Example - Class B extends Class A, Class C extends Class B. This is permitted in Java.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve inheritance object oriented programming (oops) oops concepts multiple inheritance object oriented programming (oops) oops concepts multi level inheritance object oriented programming (oops) oops concepts Basic frequent}

Very frequently asked.

Q227. 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.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve threads multithreading synchronized Asked in 5 Companies basic frequent}

Q228. Why calculations in float or Double sometimes gives unpredictable results ?

Core Java

Ans. Because the way float values are stored its not precise.

For example - 0.1 is actually stored as
0.1000000000000000055511151231257827021181583404541015625

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve double float data type basic frequent}

Q229. What different level of logging you use while coding ?

Logging

Ans. I use trace for debugging purpose. Info for displaying some important info, thought its rare as we have enabled info logging in production. Warn in case something went wrong but we still resume the flow in spite of it or have take alternate flow as its expected sometimes. Error logging in case it was completely unexpected and mostly when it breaks the flow.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve frequent}

Q230. Difference between Maven Project and Module ?

Maven

Ans. Maven Module has a Parent whereas Project doesnt. when we add the parent section to the pom file, it adds the module section to the parent project pom file. When we execute mvn compile / install, it basically checks that module section of the parent to identify all the modules that needs to be compiled first.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve maven project vs module maven project maven module frequent}

Q231. Explain Agile Software Development Methodology ?

Process

Ans. https://en.wikipedia.org/wiki/Agile_software_development

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve software development process agile Asked in 5 Companies frequent}

Q232. Difference between relational databases and NoSQL databases ?

Database

Ans. https://www.mongodb.com/scale/nosql-vs-relational-databases

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve database management nosql database relational database Asked in 1 Companies frequent}

Q233. What is a web service ?

Java EE

Ans. A Web service is a service offered by one system to another, for communication over web through http. XML are JSON are usually used for sending across information from one system to another.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve web service Asked in 2 Companies basic frequent}

Q234. Difference between Array and ArrayList ?

Core Java

Ans. <a href="http://javahungry.blogspot.com/2015/03/difference-between-array-and-arraylist-in-java-example.html" rel="nofollow">http://javahungry.blogspot.com/2015/03/difference-between-array-and-arraylist-in-java-example.html</a>

Sample Code for ArrayList

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve array arraylist Asked in 11 Companies basic frequent}

Q235. Difference between Error and Exception ?

Core Java

Ans. An Error indicates serious problems that a reasonable application should not try to catch whereas

An Exception indicates conditions that a reasonable application might want to catch.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve error exception handling exceptions Asked in 2 Companies basic frequent}

Frequently asked in Accenture.

Q236. What is your biggest achievement at work ?

General

Ans. [Open Ended Answer]

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve general question non technical question Asked in 20 Companies frequent}

Q237. What are Collection Classes ?

Core Java

Ans. Collections in java is a framework of classes that provides an abstracted data structure to store and manipulate the group of objects. Each class is unique in the way it stores , search , sort and modify the elements.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve collections collection classes Asked in 1 Companies Basic frequent}

Q238. Explain some of the http status codes you know ?

Java EE

Ans. 500 is Internal Server Error

404 is resource not found

400 is Bad Request

403 is Forbidden

401 is Unauthorized

200 is OK

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve http http status codes Asked in 2 Companies frequent}

Q239. What is Maven ?

Maven

Ans. Maven is a build automation tool used primarily for Java projects.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve maven build Asked in 6 Companies basic frequent}

Q240. Explain some of the features of Java ?

Core Java

Ans. Object Oriented - Java is object oriented but isn't purely object oriented as we have primitives along with objects.

Platform Independent - As JVM provides the translation to the Machine code as per the underlying Operating System.

Interpreted as well as compiled - Java files are compiled as class files and then class files are interpreted by JVM.

Runs on a Virtual Machine - Which is JVM that acts as an independent sub environment.

Multi-threaded - As applications can run on single thread as well as multi thread.

Modularity - Through usage of Classes , methods and Interfaces.

Robust

Usage in variety of Application types - Web , Gaming, BigData.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve frequent}

Search Interview Questions

Help us and Others Improve. Please let us know the questions asked in any of your previous interview.