Core Java - Interview Questions and Answers for 'Basic' | Search Interview Question - javasearch.buggybread.com
Javasearch.buggybread.com

Search Interview Questions


 More than 3000 questions in repository.
 There are more than 900 unanswered questions.
Click here and help us by providing the answer.
 Have a video suggestion.
Click Correct / Improve and please let us know.
Label / Company      Label / Company / Text

   



Interview Questions and Answers - Order By Newest

   next 30
 Q31. What are wrapper classes ?Core Java
Ans. They are wrappers to primitive data types. They allow us to access primitives as objects.

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

   Like         Discuss         Correct / Improve     java   data types   wrapper classes     Asked in 3 Companies      basic        frequent


Very frequently asked. Usually asked in different variants like Diff between StringBuffer , String Builder ; Difference between StringBuilder and String class; Choice between these classes etc.
  Q32. What is the difference between StringBuffer and String class ?Core Java
Ans. A string buffer implements a mutable sequence of characters. A string buffer is like a String, but can be modified. At any point in time it contains some particular sequence of characters, but the length and content of the sequence can be changed through certain method calls.

The String class represents character strings. All string literals in Java programs, such as "abc" are constant and implemented as instances of this class; their values cannot be changed after they are created.

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

   Like         Discuss         Correct / Improve     java   string   stringbuffer   frequently asked     Asked in 18 Companies      basic        frequent

Try 1 Question(s) Test


 Q33. What is JDBC? Describe the steps needed to execute a SQL query using JDBC.Database
Ans. The JDBC is a pure Java API used to execute SQL statements. It provides a set of classes and interfaces that can be used by developers to write database applications.

The steps needed to execute a SQL query using JDBC:

1. Open a connection to the database.
2. Execute a SQL statement.
3. Process th results.
4. Close the connection to the database.

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

   Like         Discuss         Correct / Improve     java   jdbc   db connectivity     Asked in 2 Companies      basic        frequent


Frequently asked to fresh graduates.
  Q34. What is a Deadlock ?Operating System
Ans. When two threads are waiting each other and cant precede the program is said to be deadlock.

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

   Like         Discuss         Correct / Improve     java   threads   multi threading   operating system   deadlock  concurrency     Asked in 23 Companies      basic        frequent


Frequently asked to fresh graduates.
 Q35. Explain Thread States ?Operating System
Ans. Runnable - waiting for its turn to be picked for execution by the thread schedular based on thread priorities.

Running - The processor is actively executing the thread code. It runs until it becomes blocked, or voluntarily gives up its turn.

Waiting: A thread is in a blocked state while it waits for some external processing such as file I/O to finish.

Sleeping - Java threads are forcibly put to sleep (suspended) with Thread.sleep. they can resume using Thread.resume method.

Blocked on I/O - Will move to runnable after I/O condition like reading bytes of data etc changes.

Blocked on synchronization - Will move to Runnable when a lock is acquired.

Dead - The thread is finished working.

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

   Like         Discuss         Correct / Improve     java   threads   multi threading   scheduling   thread states   basic interview question     Asked in 1 Companies      basic        frequent

Try 2 Question(s) Test


Very frequently asked.Usually among first few questions.
  Q36. What is MVC ? Design
Ans. MVC is a Design Pattern that facilititates loose coupling by segregating responsibilities in a Web application

1. Controller receives the requests and handles overall control of the request
2. Model holds majority of the Business logic, and
3. View comprise of the view objects and GUI component

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

   Like         Discuss         Correct / Improve     j2ee   mvc   mvc design pattern   design pattern   struts   spring   web application   web frameworks   ebay     Asked in 60 Companies      basic        frequent

Try 1 Question(s) Test


Frequently asked to fresh graduates and less experienced.
  Q37. Difference between Composition and Inheritance ?Core Java
Ans. Inheritance means a object inheriting reusable properties of the base class. Compositions means that an abject holds other objects.

In Inheritance there is only one object in memory ( derived object ) whereas in Composition , parent object holds references of all composed objects.

From Design perspective - Inheritance is "is a" relationship among objects whereas Composition is "has a" relationship among objects.

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

   Like         Discuss         Correct / Improve     java   oops   oops concepts   inheritance  object oriented programming (oops)  oops concepts   composition  object oriented programming (oops)  oops concepts   difference between   basic interview question     Asked in 12 Companies      basic        frequent

Try 2 Question(s) Test


 Q38. Difference between parameters and arguments ?Core Java
Ans. Parameters are the variables that the method is expected to receive along with the method call. Arguments are the values which are passed on while calling the methods.

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

   Like         Discuss         Correct / Improve     parameter   argument  method   function  java      basic


Frequently asked. Among first few questions in the J2EE segment of interview.
  Q39. What is deployment descriptor ?

or

What is the use of deployment descriptor ?
Java EE
Ans. Deployment Descriptor which is usually web.xml is used to specify the classes, resources and configuration of the application and how the web server uses them to serve web requests.This file is usually added to WEB-INF folder and contains following

* Servlet entries and url mapping
* Plugins
* Some info regarding authentication / filters
* Landing Page
* Event Handlers

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

   Like         Discuss         Correct / Improve     web.xml   servlets  deployment descriptor     Asked in 15 Companies      basic        frequent

Try 1 Question(s) Test


  Q40. What are the different types of inner classes ?Core Java
Ans. Simple Inner Class,
Local Inner Class,
Anonymous Inner Class,
Static Nested Inner Class.

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

   Like         Discuss         Correct / Improve     java   inner classes   classes     Asked in 6 Companies      basic        frequent

Try 1 Question(s) Test


Frequently asked in Indian Service Companies. Tech Mahindra ( Based on 3 inputs ) and Infosys ( 3 inputs )
  Q41. What is the difference between List, Set and Map ?

or

What are the different Java Collections Interfaces ?
Core Java
Ans. List - Members are stored in sequence in memory and can be accessed through index.
Set - There is no relevance of sequence and index. Sets doesn't contain duplicates whereas multiset can have duplicates.
Map - Contains Key , Value pairs.

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

   Like         Discuss         Correct / Improve     java   collections   list   set   map     Asked in 8 Companies      basic        frequent

Try 1 Question(s) Test


  Q42. Does Java support Multiple Inheritance ?Core Java
Ans. Java doesn't support multiple inheritance. Interfaces does't facilitate inheritance and hence implementation of multiple interfaces doesn't make multiple inheritance.

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

   Like         Discuss         Correct / Improve     java   oop   oop concepts   inheritence   multiple inheritence   basic interview question     Asked in 10 Companies      basic        frequent

Try 1 Question(s) Test


Frequently asked at HCL Technologies ( Based on 3 feedback )
  Q43. Difference between Checked and Unchecked exceptions ?Core Java
Ans. Checked exceptions are the exceptions for which compiler throws an errors if they are not checked whereas unchecked exceptions are caught during run time only and hence can't be checked.

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

   Like         Discuss         Correct / Improve     java   exceptions   checked exceptions   unchecked exceptions   exception handling   basic interview question     Asked in 38 Companies      basic        frequent

Try 1 Question(s) Test


Very frequently asked. Favorite question in Walk in Drive of many Indian service companies.
  Q44. What is a Final Variable ?Core Java
Ans. Final variable is a variable constant that cannot be changed after initialization.

  Sample Code for final variable

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

   Like         Discuss         Correct / Improve     oops   java   final   final variable   basic interview question     Asked in 12 Companies      basic        frequent

Try 1 Question(s) Test


 Q45. Difference between Abstract and Concrete Class ?Core Java
Ans. Abstract classes are only meant to be sub classed and not meant to be instantiated whereas concrete classes are meant to be instantiated.

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

   Like         Discuss         Correct / Improve     java   oops   abstract classes   basic interview question     Asked in 1 Companies      basic        frequent


  Q46. Difference between Vector and ArrayList ?Core Java
Ans. Vectors are synchronized whereas Array lists are not.

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

   Like         Discuss         Correct / Improve     java   basic interview question   vector   arraylist   collections   synchronization     Asked in 35 Companies      basic        frequent


Very Frequently asked. Usually asked along with String Class related questions.
  Q47. What is an immutable class ?Core Java
Ans. Class using which only immutable (objects that cannot be changed after initialization) objects can be created.

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

   Like         Discuss         Correct / Improve     java   oops   immutable  immutability   immutable  immutability class   string class   basic interview question     Asked in 18 Companies      Basic        frequent

Try 2 Question(s) Test


Frequently asked to fresh graduates.
  Q48. Difference between Process and Thread ?Operating System
Ans. Process is a program in execution whereas thread is a separate path of execution in a program.

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

   Like         Discuss         Correct / Improve     java   threads   multi threading   operating system   basic interview question     Asked in 24 Companies      basic        frequent


 Q49. Explain Autoboxing ?Core Java
Ans. Autoboxing is the automatic conversion that the Java compiler makes between the primitive types and their corresponding object wrapper classes

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

   Like         Discuss         Correct / Improve     java   java5   autoboxing   wrapper classes     Asked in 2 Companies      basic        frequent


Very frequently asked. Usually difference between String,StringBuffer and StringBuilder is asked in different variations.
  Q50. Difference between StringBuffer and StringBuilder ?Core Java
Ans. StringBuffer is synchronized whereas StringBuilder is not.

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

   Like         Discuss         Correct / Improve     java   string   stringbuffer   string class   stringbuilder   synchronized   basic interview question   infosys technologies     Asked in 17 Companies      basic        frequent

Try 1 Question(s) Test


  Q51. What is reflection ?
Ans. It is the process of examining / modifying the behaviour of an object at runtime.

  Sample Code for reflection

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

   Like         Discuss         Correct / Improve     java   reflection   reflection api   ebay   mindtree     Asked in 29 Companies      basic        frequent


 Q52. Similarity and Difference between static block and static method ?Core Java
Ans. Both belong to the class as a whole and not to the individual objects. Static methods are explicitly called for execution whereas Static block gets executed when the Class gets loaded by the JVM.

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

   Like         Discuss         Correct / Improve     java   oops   static   static method   static block   difference between   similarity      basic        frequent

Try 1 Question(s) Test


Very Frequently asked.
 Q53. 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.

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

   Like         Discuss         Correct / Improve     java   exception handling   throw   throws   try   catch     Asked in 2 Companies      basic        frequent


  Q54. Difference between GET and POST Requests ?Web Service
Ans. GET is supposed to get information from the server. Client sends the minimal information so that Server can respond with the response body on basis of request. For example - You want to get complete employment record for employee id 123

POST is supposed to send the information for submission. Payload or a Body is usually sent so that it can be persisted on the server. For example - Sending the complete information of an employee ( id, name , dept etc ) to the server for persisting it.

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

   Like         Discuss         Correct / Improve     get vs post   web service   rest     Asked in 11 Companies      basic        frequent


 Q55. Difference beween HashSet and TreeSet ?Core Java
Ans. 1. HashSet doesnt maintain its elements in any specific order and is all random whereas TreeSet maintains elements in natural order 9 order defined by the equals method of TreeSet element type )

2. TreeSet doesnt allow null elements whereas HashMap does.

3. As TreeSet orders elements and is hence insertion is comparatively slower.

4. HashSet performs basic operations like add(), remove(), contains(), size() etc. in a constant size time. A TreeSet performs these operations at the order of log(n) time.

5. HashMap in Java internally backs a HashSet. A NavigableMap backs a TreeSet internally.

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

   Like         Discuss         Correct / Improve     collections  hashset  treeset  set     Asked in 4 Companies      Basic        frequent

Try 1 Question(s) Test


 Q56. If an Abstract class has only abstract methods, What's the difference between such a class and an interface ?Core Java
Ans. Such a class still can have member elements which can be inherited and hence facilitate code reuse. Moreover Abstract class can have non final static elements whereas interfaces are only allowed to have static final elements.

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

   Like         Discuss         Correct / Improve     abstract class   interfaces     Asked in 2 Companies      Basic


 Q57. What is the difference between inner class and sub class ?Core Java
Ans. Inner Class is a class that is nested within another class whereas sub class is a class that extends or inherit another class.

Inner class can only be accessed using reference of outer class ( Class name , if inner class is static or object reference, if inner class is non static ) whereas Sub class is accessed directly.

In terms of memory, inner class is stored just like another class having it's own body whereas sub class carries the body of parent class as well as it's own fields in memory.

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

   Like         Discuss         Correct / Improve     inner classes  nested classes  inner class vs sub class  nested class vs sub class      Basic


  Q58. What is JSON ?Json
Ans. JSON is "JavaScript Object Notation", primarily used for client-server or server-server communication. Its a much lighter and readable alternative to XML. JSON is language independent and is easily parse-able in all programming languages.

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

   Like         Discuss         Correct / Improve     json   markup language   client server communication     Asked in 26 Companies      basic        frequent

Try 2 Question(s) Test


 Q59. What is an API ( Application Programming Interface ) ?
Ans. An API is a kind of technical contract which defines functionality that two parties must provide: a service provider (often called an implementation) and an application. an API simply defines services that a service provider (i.e., the implementation) makes available to applications.

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

   Like         Discuss         Correct / Improve     j2ee   api   java      basic        frequent


 Q60. What is URL?
Java EE
Ans. URL is Uniform Resource Locator which is representation of HTTP address.

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

   Like         Discuss         Correct / Improve     j2ee   http   internet   url      basic        rare


previous 30   next 30

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

Any input from you will be highly appreciated and It will unlock the application for 10 more requests.

Company Name:
Questions Asked: