Hindustan Unilever Limited JavaEE experienced interview questions

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                       JavaEE  Interview  Question  for  Experienced Professinal

        

What is the difference between Interface and Abstract class?​

Abstract  class	Interface
class  extends  only one abstract  class	Class can extends  many interfaces
Abstract  can have  non  abstract  methods	All  methods  of  interface  is  abstract   type.
Abstract  class can have  all  access modifiers .	In interface  public modifiers
Abstract classes  are  for  design  suitable	Interface  for implementation .

What are the different ways to handle exceptions?

Ans :    There  are two  ways  to handle the  exceptions   1.  wrapping the  code in to try

             catch   and finally block.

              2.  Throwing  method  generated  exception  using throws  keyword

What is the use of Wrapper class?

Ans: A Wrapper  class is a class   whose object wraps or contains a primitive data types. When we create an object to a wrapper class,  it contains a field and in this field,   we can store a primitive data types. In other words, we can wrap   a primitive value  into a wrapper class object.

Difference between string literal and string object?

Ans -    String  literals  are when we  declare  string directly .  But   string  object  declare

             using new keyword .

                String  st = new  String “Mukesh” ;

                String  str=new  String (“Mukesh”);

     Object  slower then literal   in executions 

Tell about Map interface?

Ans—     Map  is  collection   interface  .  Stores     elements  as key  and  value  pair .

      Map  can have  one Null  key and multiple  null value. 

What is synchronization?

Ans -  Synchronisation   is technique  to  access   one  object  by  multiple  Thread  at a

  time . This  can be  achieve   using  lock the  object .

What is the purpose of finalization?

Ans -  Finalisation   is  method    for  garbage  collection . This   method  is call  for  garbage  collection .

What is autowiring in Spring?

Ans- Autowiring   is  used to  call  one bean   in to  another bean . @autowire  annotation  is used for this  purpose .  Auto wiring   are  type  none ,  byname , by type .

 List the different Scopes of Spring bean?

Ans-  Singleton , prototype  request , session , global session

What is the use of AOP?

Ans - AOP   stats     Aspect oriented  programming .  This   useful when  we need to  big  source  code   into small  modules.

What is the DispatcherServlet?

 Ans   DispatcherServlet  is   servlet  which   use  as  front controller . DispatcherServlet

         take the  spring request and  contact  Handler Mapper ,  then  contact controller  and  filly

         view resolver  to give response   of the request . 

Difference between GET and POST?

GET	POST
GET  is not vary  secure  to  send  the data in browser	Post  is secure  to send the data.
Can be  bookmarked	Can’t be bookmarked
Can cashed	Can't  be cashed

 

What is Hibernate Caching?

Ans -   Hibernate   cashing   is technique  to   prevent  repetitive   hit of the  data table.

             two  type of  cashing   hibernate  provide

                 1. First   level cash (session level )

                 2.  Second level cash .   

What is named Query?

Ans-The hibernate named query is way to use any query by some meaningful name. It is like using alias names. The Hibernate framework provides the concept of named queries so that application programmer need not to scatter queries to all the java code.

What is HQL?

Ans -  Hibernate Query Language (HQL) is an object-oriented query language, similar to SQL, but instead of operating on tables and columns, HQL works with persistent objects and their properties. HQL queries are translated by Hibernate into conventional SQL queries, which in turns perform action on database.

What is inner join?

Ans-The INNER JOIN selects all rows from both participating tables as long as there is a match between the columns. An SQL INNER JOIN is same as JOIN clause, combining rows from two or more tables.

SELECT *

FROM table1 INNER JOIN table2

ON table1.column_name = table2.column_name;

How to invoke stored procedure from java?

Ans - Store procedure  is   called using  CallableStatement  in Java .

   this  is  sample of the code  we can use for  that

    CallableStatement cstmt = null;

try {

   String SQL = "{call getEmpName (?, ?)}";

   cstmt = conn.prepareCall (SQL);

   . . .

}

catch (SQLException e) {

   . . .

}

finally {

   . . .

}

How to handle PL/SQL exceptions?

Ans —  The    PL/SQL  handles  used    when  and  then key  word  to handle  exception . Here

           it   is   a   sample of the   code.

             DECLARE

   <declarations section>

BEGIN

   <executable command(s)>

EXCEPTION

   <exception handling goes here >

   WHEN exception1 THEN 

      exception1-handling-statements 

   WHEN exception2  THEN 

      exception2-handling-statements 

   WHEN exception3 THEN 

      exception3-handling-statements

   ........

   WHEN others THEN

      exception3-handling-statements

END;

What is Sequence?

Ans:—

Sequence is a feature supported by some database systems to produce unique values on demand. Some DBMS like MySQL supports AUTO_INCREMENT in place of Sequence.

Sequence can represent  a  row uniquely.

Tell about basic JUnit annotations?

Ans-::   Here     are basic   annotations used in the JUnit .

@BeforeClass – Run once before any of the test methods in the class, public static void.

@AfterClass – Run once after all the tests in the class have been run, public static void.

@Before – Run before @Test, public void.

@After – Run after @Test, public void.

@Test -

@Ignore  -  To ignore  some the test