java interview question

OOPS

• Concepts

Differences

• aggregation and composition
• Abstraction and Encapsulation

Java

• What is static variable. transient variable. volatile variable, final variable.
• What are the kinds of variables in Java? (Instance, Class, Local)
• What is method overloading and s method overriding?
• What is final method, native method. abstract method ?
• synchronization is to be applied only for?
• What is anonymous class.
• What is Adapter classes
• What are wrapper classes
• What are different types of inner classes?
• Can you instantiate the Math class?
• Can the abstract class be final?
• Can a top level class be private or protected?
• Is null a keyword?
• What is JVM?
• What is a Tagged interface Interface? Examples ?
• What do you mean by a Classloader?
• How will you execute any method of the superclass from the subclass?
• What is the purpose of the File class?
• What is the life cycle of an applet.
• What is Reflection. Uses of Reflection.
• How do I access environment variables?
• What does autoboxing and unboxing mean?
• What are annotations in Java?
• can you force garbage collection?
• What is the purpose of finalization?
• Access Modifiers and access Specifiers ?
• Hierarchy of exception
• What are Checked and UnChecked Exception?
• What are runtime exceptions?
• What are the different ways to handle exceptions?
• What is the purpose of the finally clause of a try-catch-finally statement?
• Does the code in finally block get executed if there is an exception and a return statement in a catch block?
• What is User defined exception?
• What are different ways in which a thread can enter the waiting state?
• What are the various ways of creating a thread
• Three types of priority? (MAX_PRIORITY which is 10, MIN_PRIORITY which is 1, NORM_PRIORITY which is 5)
• What is deadlock?
• Algorithm used in Thread scheduling? (Fixed priority scheduling.)
• Usually where we use the methods wait(), notify(), and notifyAll() methods?
• What is the common usage of serialization?
• How many methods in the Serializable interface and it's package is?
• What is Externalizable?
• How many methods in the Externalizable interface?
• How do I synchronize a collection
• What interface do you implement to do the sorting?
• What is a hashCode and where will you use it ?
• What is HashMap and Map?

Differences

• JVM and JDK and JRE
• Abstract class and Interface.
• Hashmap and Hashtable.
• Vector, Array and Arraylist.
• Final, finally and finalized.
• String and StringBuffer.
• Exception and error.
• List, Set and Map.
• this() & super().
• Iterator and Enumeration.
• wait(), join(), sleep(), notify() & notifyall()
• File and RandomFileAccess classes.
• paint() and repaint() methods.
• yielding and sleeping.
• .equals and ==
• URL & URI
• & operator and the && operator?
• JDBC
• What are the classes you used in JDBC ?
• ACID properties
• What is the purpose of setAutoCommit().
• What are batch updates and how you will write it?
• What are the steps for connecting to the database using JDBC.
• What is Connection Pooling? How do you implement Connection Pooling?
• What Class.forName() method will do.?
• What happens if I close the connection twice?
• What are the standard isolation levels defined by JDBC? (TRANSACTION_NONE, TRANSACTION_READ_COMMITTED, TRANSACTION_READ_UNCOMMITTED, TRANSACTION_REPEATABLE_READ, TRANSACTION_SERIALIZABLE)
• How do I receive a ResultSet from a stored procedure?
• Types of Drivers

Differences

• Statement, PreparedStatement, Callable Statement
• execute, executeQuery, executeUpdate
• Resultset and Rowset
• JDBC 2.0 and JDBC 2.1
• Why cannot java.util.Date match with java.sql.Date?

JSP

• Life cycle of JSP.
• What are Custom tags? And how will implement the custom Tags and how do you configure it.
• What are the implicit objects in JSP
• What are the scope attributes & difference between them(level hierarchy of scopes) ?
• What is difference between scriptlet and expression?
• How do you handle exception handling in JSP
• How do you implement thread safe in JSP
• Tell some of the attributes of Page
• Can we implement an interface in a JSP?
• If I want to upload a file what attribute am I going to use in form tag (ENCTYPE="multipart/form-data")
• How can I display different currencies in my JSP pages according to the location of the client. (request.getLocale() and passing it to a NumberFormat object).
• What is a translation unit?
• What is Expression ,is Declaration and Scriptlet?
• What are Standard Actions in JSP ?
• Attributes of <jsp:useBean> tag
• How do I prevent the output of my JSP or Servlet pages from being cached by the browser?

Differences

• include directive & jsp:include action
• page vs pagecontext?

Servlets

• What are Servlets
• What is the Life cycle of Servlet?
• Can destroy() be called from inside the service() method
• Can I make service() method synchronized? if I do so then what will happen if ten user access that Servlet
• Preinitializtion of Servlet
• Servlet Aliasing
• How to redirect from one servlet to another servlet present in another container ?
• How do you implement SingleThreadModel in Servlets?
• Server side include ?
• Servlet Realms
• How do you invoke the the servlet using the Basic authentication
• How do restrict access to the servlets package.
• 
  
• How to you pass parameter using HtppUrlConnection
• How can I send user authentication information while making URLConnection? (HttpURLConnection.setRequestProperty)
• How to get the url of the current request
• What is filter? Why do we need filter and how do you configure filter
• What is Listener Why do we need listener and how do you configure listener
• What is Session Tracking? various ways for achieving SessionTracking
• Various ways of specifying Session Time out ? Mention all the mechanisms?
• How you will achieve Servlet collabaration ?
• What is the tag used for specifying the datasource
• How many cookies can one set in the response object of the Servlet
• hot many ways a Servlet to Servlet communication ?
• What is HTTP tunneling
• Explain the directory structure of a web application.

Differences

• Servlet and JSP
• sendRedirect() & forward() method.
• doGet() and doPost()
• HTTPServlet and GenericServlet.
• rd.forward(); or rd.include();
• request.getAttribute() and request.getParameter()?
• ServletContext and PageContext
• ServletContext and ServletConfig?
• ServletContext.getInitParameter() and HttpServlet.getInitParameter() ?

EJB

• 
  
• What is EJB
• Key Benefits of uisng EJB
• Different kinds of EJB
• What is Session Bean
• What is Entity Bean
• What is Message driven Bean
• What are the methods of Entity Bean?
• What are the callback methods in Entity beans?
• Can Entity Beans have no create() methods?
• How EJB Invocation happens?
• Is it possible to specify multiple JNDI names when deploying an EJB?
• How many types of protocol implementations does RMI have?
• Life cycle of EJB's
• Procedure for writing EJB's
• what are the call back methods in Session bean
• What are the call back methods in Entity bean
• Transaction models
• Transaction attributes?
• What is the default transaction attribute for an EJB?
• Can you create thread in EJB
• which one do you prefer to use HTTPSession or Stateful Session Bean
• Without looking at the deployment descriptor how can you say that ejb is stateful or stateless
• How can I pass init parameters to enterprise beans?
• Can I invoke Runtime.gc() in an EJB?
• Can a Session Bean be defined without ejbCreate() method?
• Marshalling and unmarshalling?
• What is lazy loading
• <ejb-link>
• Explain the directory structure of a enterprise application
• What are the various services provided by the EJB Container
• EJB QL
• How is Stateful Session bean maintain their states with client
• Architecture used by the passivation
• Architecture used by the activation
• Can you control when passivation occurs?
• what are the methods available in session synchronization
• Does Stateful Session bean support instance pooling?
• In Session Beans can I use BM and CM transaction at a time (NO)
• What is abstract schema
• Can I map more than one table in a CMP?
• Is it possible to update the Primary key of the entity bean
• What is a cmr-field. How can I differentiate between a cmr-field and a cmp-field?
• What is an ejbSelect() method?
  1. ejbSelect method(s) are not exposed to the client and the ejbSelect method(s) can return values that are defined as cmp-types or cmr-types.
• ejbSelect & find

Differences

• Instance Pooling & Instance Swapping
• ejbActivate & ejbPassivate
• ejbLoad & ejbStore
• EJB 1.1 and EJB 2.0
• CMP1.1 & 2.0
• local interface and remote interface
• Coarse grained & Fine grained
• BMP & CMP
• EJB Container & Web Container
• Application Server & Web Server
• sessioncontext and entitycontext
• optimistic locking and pessimistic locking
• ejbCreate() and ejbPostCreate().
• Servlet Sesison & EJB Session
• Container Managed Persitence 1.1 and 2.0
• ejbSelect vs finder methods
• Context, InitialContext and Session Context?
  1. Context is an interface that provides methods for binding a name to an object
  2. InitialContext is a Context and provides implementation for methods available in the Context interface
  3. SessionContext is an EJBContext object that is provided by the EJB container to a SessionBean in order for the SessionBean to access the information and/or services or the container
• Context, InitialContext and Session Context?

Struts

• Explain Struts Architecture ?
• how will you Internalization
• Validation Framework
• How do you display validation Errors to the client ?
• What is Request Processor ?
• Various design patterns used by the Struts Framework
• Tell me what all you mention in Struts-config.xml sequentially ?
• What are the various Struts tag libraries you used ?
• Explain about token feature in Struts ?
• Multibox and checkbox ?
• purpose of LabelValueBean?
• How many ways you can handle the exception/errors?
• Calling a Action Class from another Action class

Difference

• Action Errors & Action Messages
• bean:write vs bean:message ?
• DispatchAction & Action, LookupDispatchAction
• ActionForm & DynaActionForm
• MVC1 & MVC2

Design Patterns

• DAO Patterns ,Singleton pattern, Value Object pattern, Session facade pattern , Business delegate pattern, decorator pattern, Factory pattern ,Service Locator pattern ,MVC Architecture

Difference

Pattern & Framework and API & Framework

XML

• What is the difference between SAX parser and DOM parser.
• What is the difference between Schema and DTD.
• How do you parse/validate the XML document.
• What is XML Namespace.
• What is Xpath.
• How would you produce PDF output using XSL's.
• What are the steps to transform XML into HTML using XSL.
• What is XSL and XSLT.

HTML and Js:

• window.history()
  form vs document
  Types of dialog boxes?
  <Html:link>
  <html:base>
  purpose of <iframe>
  
• how you will return all the objects of a specific element to return ?

SQL

• How to create a table (including data) with selected columns of another table?
• DDL ,DML and DCL?
• Order of order by , group by. Where, having ?
• Materialized view ?
• Write a query to display n maximum salaries
• What are the pseudo columns in oracle? (rowid, rownum)
• Difference between procedure and function?
• Difference between varchar and varchar2?
• Can a table have more than one primary key?
• Difference between IN and EXISTS
• truncate , drop and delete?
• How can we handle exceptions in PL/SQL
• Join, Inner joins, Outer Joins
• How do you create Index. Advantages of Index
• View is physical Database Object or Logical Database object. Can we modify the View ?
• What are triggers and types of triggers ?
• What is cursor and types?
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• Can we override a constructor if yes, what will happend?
• Difference b/w instanceOf and isInstance ?
• How can you restrict finally block to not to execute ?
• How to make a class immutable ?
• Where you will use inner classes ?
• In thread creation which mechanism is good and why ?
• equals() vs hashCode() ?
• Collection vs Collecions ?
• Can we serialize static data ?
• Can i add duplicate keys/values into hashmap, what will happen ?
• I have to do many insert/delete operation on a collection, which one you will use?
• .can we have multiple struts-config.xml, how ?
• How to configure log4j in your application?
• How to configure ResourceBundle in your application?
• Levels of loggers?
• What all you mention in logger properties?
• How to set class level logger ?
• ANT means ? Alternatives to ANT ?
• Web container and app server ?
• Jboss vs Weblogic ?
• Authentication vs authorization ?
• Tell me Authentication mechanisms by the container ?
• What all you will mention in Deployment Descriptor ?
• If i have 100 requests hitting a servlet, this scenario how many instances will be created and how ?
• How you will count the no.of users accessing an application ?
• JAR vs WAR vs RAR ?
• Purpose of filters and listeners ?
• How to restrict browser cashing ?
• How a make a particular JSP to refresh continuously?
• Types of comments in JSP(output and hidden) ?
• Jspwriter vs Printwriter ?
• How to send a mail ?
• JNDI ?
• What is Ripple Effect?