Interview Questions

Our Java questions and answers focus on all areas of Java programming language covering 350+ topics in Java. These topics and Questions are taken from Mr. Shashi Kumar from SSSIT, KPHB, Hyderabad-72.

You can contact him Through SSSIT from here <Link>

Highlights

- Interview Questions Faced by Mr. Shashi Kumar

- Questions & Answers in Java with explanations

- Every MCQ set focuses on a specific topic in Java Language

Let’s Get Started & Continue Reading…………………………….

1.First Interview: 10-10-2009

1)How many ways are there to create an object?

i) Using ‘new’ operator:

Test s=new Test();

ii) Factory method:

Thread t=Thread.currentThread();

iii) newInstance():

Class c=Class.forName(“Test”);

Object obj=c.newInstance(); àcreates Test class Object.

Test t=(Test)obj;

Continue Reading…………………………….

iv) clone():

Test t1=new Test(10,20);

Test t2=t1.clone();

v) Deserialization:

FileInputStream fis=new FileInputStream(“Test.txt”);

ObjectInputStream ois=new ObjectInputStream(fis);

UserDefSerCls uds=new UserDefSerCls(,” ”,);

Ois.readObject(uds);

Ois.close();

2) What are the differences b/w HashMap and HashSet?

HashMap	HashSet
It stores the data in key,value format. It allows duplicate elements as values. It implements Map It allows only one NULL key.	It stores grouped data . It does not allow any duplicates. It implements Set. It does not allow NULL .

3) What is the difference b/w wait(-), sleep(-)& wait(-),yield()?

Wait(-)

Sleep(-)

Running to Waiting/ Sleeping/Block. It makes the current thread to sleep up to the given seconds and it could sleep less than the given seconds if it receives notify()/notifyAll() call. In this case, the locks will be released before going into waiting state so that the other threads that are waiting on that object will use it. Causes current thread to wait until either another thread invokes the notify() method or the notifyAll() method for this object, or a specified amount of time has elapsed.

Do It makes the current thread to sleep for exactly the given seconds. In case of sleep(), once the thread is entered into synchronized block/method, no other thread will be able to enter into that method/block.

Yield()à when a task invokes yield(), it changes from Running state to Runnable state.

*4) Can we create a userdefined immutable class?

Yes.

i) Make the class as final and

ii) make the data members as private and final.

*5) What are the differences b/w String and StringBuffer?

String	StringBuffer
It is immutable. It won’t give any additional space.	It is mutable. gives 16 additional characters memory space.

6) Which “Collections F/W” classes did you use in your project?

List, ArrayList, LinkedList—add()

Set, TreeSet, HashSet--

HashMap—put(), get(), entrySet(), keyset()

Map.Entry

Iterator----hasMoreElements(), next()

ListIterator.

7) Can you write the simple code for HashMap?

HashMap<String,String> hm=new HashMap<String,String>();

hm.put(“key1”,”value1”);

hm.put(“key2”,”value2”);

hm.put(“key3”,”value3”);

Set set=hm.keySet(); // gives keys Set i.e., {key1,key2,key3}

Iterator<string> itr=set.iterator();

while(itr.hasNext()){ //true….false

String empkeys=itr.next(); //for keys

String empvalnames=hm.get(empkeys); //gives values by taking keys.

System.out.println(“empname”+empvalnames+”empid”+empkeys);

}

8) What are thread states?

i) Start: Thread thread=new Thread();

ii) Runnable: looking for its turn to be picked for execution by the Thread Schedular based

on thead priorities. (setPriority())

iii) Running: The Processor is actively executing the thread code. It runs until it becomes

blocked, or voluntarily gives up its turn with Thread.yield().

Because of Context Switching overhead, yield() should not be used very

frequently.

iv) Waiting: A thread is in a blocked state while it waits for some external processing such

as file I/O to finish.

Sleepingàsleep(): Java threads are forcibly put to sleep (suspended) with this overloaded method.

Thread.sleep(milliseconds); Thread.sleep(milliseconds,nanoseconds);

Blocking 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.

v) Dead: The thread is finished working.

How to avoid Deadlock:

1) Avoid a thread holding multiple locks----

If no thread attempts to hold more than one lock ,then no deadlock occurs.

2) Reordering lock acquisition:--

If we require threads to always

acquire locks in a particular order, then no deadlock occurs.

2.Oracle Corporation:- 15-11-2009

9) What are differences b/w concrete,abstract classes and interface & they are given?

Concrete class: A class of only Concrete methods is called Concrete Class.

For this, object instantiation is possible directly.

A class can extends one class and implements many interfaces.

Abstract class:

Interface:

*A class of only Concrete or only Abstract or both. *Any java class can extend only one abstract class. *It won’t force the programmer to implement/override all its methods. *It takes less execution time than interface. * It allows constructor. This class can’t be instantiated directly. A class must be abstract when it consist at least one abstract method. It gives less scope than an Interface. It allows both variable & constants declaration. It allows methods definitions or declarations whenever we want. It gives reusability hence it can’t be declared as “final”.

only abstract methods. A class can implements any no. of interfaces (this gives multiple interface inheritance ) It forces the programmer to implement all its methods Interface takes more execution time due to its complex hierarchy. * It won’t allow any constructor. It can’t be instantiated but it can refer to its subclass objects. It gives more scope than an abstract class. By default, methodsàpublic abstract variablesàpublic static final. It allows methods declarations whenever we want . But it involves complexity. Since they give reusability hence they must not be declared as “final”.

10) Can you create a userdefined immutable class like String?

Yes, by making the class as final and its data members as private, final.

11) Name some struts supplied tags?

a) struts_html.tld b) struts_bean.tld

c) struts_logic.tld d) struts_nested.tld

d) struts_template.tld e) struts_tiles.tld.

12) How to retieve the objects from an ArrayList?

List list=new ArrayList(); // List<String> list=new ArrayList<String>();

list.add(“element1”); list.add(“element1”);

list.add(“element2”); list.add(“element2”);

list.add(“element3”); list.add(“element3”);

// Iterator<String> iterator=list.iterator();

for(String str:list)

s.o.p(str); }

Iterator iterator=list.iterator();

while(iterator.hasNext()){

String str=(String)itr.next();

S.o.p(string);

}

}

13) What are versions of your current project technologies?

Java 5.0; Servlets 2.4, Jsp 2.0; struts 1.3.4 ; spring 2.0; Hibernate 3.2, Oracle 9i. weblogic 8.5.

14) What is “Quality”?

It is a Measure of excellence.

state of being free from defects, deficiencies, and significant variations.

A product or service that bears its ability to satisfy stated or implied needs."

15) Can I take a class as “private”?

Yes, but it is declare to inner class, not to outer class.

If we are declaring "private" to outer class nothing can be

accessed from that outer class to inner class.

16) How can you clone an object?

A a1=new ();

B a11=a1.clone();

17) What methods are there in Cloneable interface?

Since Cloneable is a Marker/Tag interface, no methods present.

When a class implements this interface that class obtains some special behavior and that

will be realized by the JVM.

18) What is the struts latest version?

Struts 2.0

19) How are you using “Statement” like interface methods even without knowing their

implementations classes in JDBC?

20) Which JSP methods can be overridden?

jspInit() & jspDestroy().

21) Explain the JSP life-cycle methods?

1. Page translation: The page is parsed & a Java file containing the corresponding servlet is

created.
2. Page compilation: The Java file is compiled.
3. Load class: The compiled class is loaded.
4 .Create instance: An instance of the servlet is created.
5. Call jspInit(): This method is called before any other
method to allow initialization.
6. Call _jspService(): This method is called for each request. (can’t be overridden)
7. Call jspDestroy(): The container calls this when it decides take the instance out of service.

It is the last method called n the servlet instance.

3.Date:17-11-2009- Telephonic

22) What Design Patterns are you using in your project?

i) MVCàseparates roles using different technologies,

ii) Singleton Java classàTo satisfy the Servlet Specification, a servlet must be a Single

Instance multiple thread component.

iii) Front Controllerà A Servlet developed as FrontController can traps only the requests.

iv) D.T.O/ V.OàData Transfer Object/Value object is there to send huge amount of data

from one lalyer to another layer.

It avoids Network Round trips.

v) IOC/Dependency Injectionà F/w s/w or container can automatically instantiates the

objects implicitly and injects the dependent data to that object.

vi) Factory methodà It won’t allows object instantiation from out-side of the calss.

vii) View Helperà It is there to develop a JSP without Java code so that readability,

re-usability will become easy.

23) What is Singleton Java class & its importance?

A Java class that allows to create only one object per JVM is called Singleton Java class.

Ex: In Struts f/w, the ActionServlet is a Singleton Java class.

Use: Instead of creating multiple objects for a Java class having same data, it is recommended

to create only one object & use it for multiple no. of times.

24) What are the differences b/w perform() & execute()?

perform() is an deprecated method.

25) What are the drawbacks of Struts? Is it MVC-I or II? Struts is MVC-II

1) Struts 1.x components are API dependent. Because Action & FormBean classes must

extend from the Struts 1.x APIs pre-defined classes.

2) Since applications are API dependent hence their “Unit testing” becomes complex.

3) Struts allows only JSP technology in developing View-layer components.

4) Struts application Debugging is quite complex.

5) Struts gives no built-in AJAX support. (for asynchronous communication)

Note: In Struts 1.x, the form that comes on the Browser-Window can be displayed

under no control of F/W s/w & Action class.

26) What are the differences b/w struts, spring and hibernate?

Struts: allows to develop only webapplications and

it can’t support POJO/POJI model programming.

Spring: is useful in developing all types of Java applications and

support POJO/POJI model programming.

Hibernate: is used to develop DB independent persistence logic

It also supports POJO/POJI model programming.

27) What are differences b/w Servlets & Jsp?

Servlets:

i) It requires Recompilation and Reloading when we do modifications in a Servlet.(some servers)

ii) Every Servlet must be configured in “web.xml”.

iii) It is providing less amount of implicit objects support.

iv) Since it consists both HTML & B.logic hence modification in one logic may disturbs

the other logic.

v) No implicit Exception Handling support.

vi) Since it requires strong Java knowledge hence non-java programmers shows no interest.

vii) Keeping HTML code in Servlets is quite complex.

JSP:

i) No need of Recompilation & Reloading when we do modifications in a JSP page.

ii) We need not to Configure a JSP in a “web.xml”.

iii) It is providing huge amount of Implicit Objects support.

iv) Since Html & Java code are separated hence no disturbance while changing logic.

v) It is providing implicit XML Exception Handling support.

vi) It is easy to learn & implement since it is tags based.

vii) It allows to develop custom tags.

viii) It gives JSTL support.

(JSP Standard Tag LibraryàIt provides more tags that will help to develop a JSP

without using Java code).

ix) It gives all benefits of Servlets.

28) What is the difference b/w ActionServlet & Servlet?

ActionServlet: It is a predefined Singleton Java class and it traps all the requests

coming to Server. It acts as a Front-Controller in Struts 1.x.

Servlet: a Java class that extends HttpServlet/GenericServlet or implements Servlet

interface and is a Server side technology to develop dynamic web pages.

It is a Single instance multiple thread component. It need not be a Singleton Java class.

29) What are Access Specifiers & modifiers?

i) public- à Universal access specifier.

--can be used along with: class, innerclass, Interface, variable, constructor, method.

ii) protectd à Inherited access specifier.

--can be used along with: innerclass, variable, method, constructor.

iii) default à Package access specifier(with in the package).

--can be used along with: class, innerclass, interface, variable, constructor, method.

iv) private à Native access specifier.

-- can be used along with: innerclass, variable, constructor, method.

à Some other access modifiers:

i) static------------innerclass,variable,block,method.

ii) abstract—----- class,method.

iii) final--------------class,variable,method.

iv) synchronized---block,method.

v) transient---------variable.

vi) native-------------method.

vii) volatile-----------variable

viii) strict fp-----------variable

30) Which JSP tag is used to display error validation?

In Source page:

<%@page errorPage=”error-page-name.jsp”>

In Error page:

<%@page isErrorPage=”true”>

31) What are the roles of EJBContainer ?

• An EJB container is the world in which an EJB bean lives.
• The container services requests from the EJB, forwards requests from the client to the EJB, and interacts with the EJB server.
• The container provider must provide transaction support, security and persistence to beans.
• It is also responsible for running the beans and for ensuring that the beans are protected from the outside world.

32) If double is added to String then what is the result?

Double + String=String

4.CrimsonLogic-Murugeshpalya-kemfort- 18-11-2009

33) What is Ant? What is its use

Ant is a tool that is used to build war, compilation, deploy.

34) What is log4j? What is its functionality?

Log4j is a tool used to display logger messages on a file/console.

<appender name="CONSOLE" class="org.apache.log4j.ConsoleAppender">

< appender name="FILE" class="org.apache.log4j.FileAppender">

logger.debug("Hi");

logger.info("Test Log");

logger.error()

Logger logger = Logger.getLogger(SampleLogtest.class);

35) What are the functions of service()?

      

protected void service(HttpServletRequest req,HttpServletResponse resp)

                                   throws ServletException, java.io.IOException

Receives standard HTTP requests from the public service method and dispatches them to the doXXX methods defined in this class. This method is an HTTP-specific version of the

   public void service(ServletRequest req, ServletResponse res)

                                      throws ServletException, java.io.IOException

Dispatches client requests to the protected service method. 

There's no need to override this method.

36) How do we get the container related information?

By using “ServletContext” object.

37) What is a Singleton Pattern?

is a design pattern that is used to restrict instantiation of a class to one object. 

class Single{

private static Single s=null;

private Single(){

------}

public static Single Factory(){

if(s==null)

return( new Single());

}

}

38) What are the functions of a Filter Servlet?

It traps all the requests & responses. 

Container creates the Filter object when the web application is deployed.

39) How to compile a JSP page? 

Jasper tool-tomcat; 

Jspc tool--weblogic

40) What is Hidden variable and give its snipplet HTML code?

    

     <input type="hidden" id="age" name="age" value="23" />

     <input type="hidden" id="DOB" name="DOB" value="01/01/70" />

     <input type="hidden" id="admin" name="admin" value="1" />

41) How do you forward Servlet1 request to Servlet2?

ServletContext sc=getServletContext();

RequestDispatcher rd =sc.getRequestDispatcher(“/s2url”); //” or html file name”

rd.forward(req,resp);

(or) rd.include(req,resp);

5. Telephonic Interview: 23-11-2009.. MindTree

42) differences b/w a Vector & a ArrayList?

ArrayList	Vector
1. One dimensional data structure  2. New Collections F/w class 3. Non-synchronized 4. Serialized	Do Legacy Collection F/W class Synchronized Non-serialized

43) try{ ----code for calling a not existed file---}

catch(Exception){--------}

catch(FileNotFoundException){-------}// for catch blocks no order significance.

Which “catch” block will be executed?

Compile time Error comes.

44) types of Action classes?

Actionàconsists b.logic or logic that is there to communicate with other Model like EJB, 

Spring..

DispatchActionàan Action class used to group similar action classes having different methods.

The name of the method will be coming in the request.

45) How do you print the missed salaries of employees?

User table Salary table 

user_id user_id;

user_name user-salary;

print user-id,user-name,user-sal;

select user-id, user-name, user-sal from User us, Salary sal where us.user-id=sal.user-id.

46) What is “IN”, “OUT”, “INOUT” parameters?

in, out, inout are the modes of the variables in PL/SQl.

“ in” is input variable mode.

“out” is output variable mode.

“inout” is in-out variable mode.

6. Date: 12-12-2009 

Venue: NIIT technology, Silk Board, Begur Hobli, Hosur Main Road.

Bus:from RRNagar to BanShankari---225c. Banshankari to SilkBoard—5001c

TECHNICAL ROUND: time: 1.30 pm to 2.45 pm

47) How can you achieve Concurrence in Java? 

Using Multithreading

48) How to implement Synchronization? Can we use synchronized with variables?

using the synchronized modifier along with the method or block.

We cant synchronized a variable.

49) What classes are there in Spring Environment?

Spring config.xml. spring bean class, spring bean interface.

50) What are the common files when 5 or more projects are developed using Hibernate ?

Configuration file

51) What are the differences b/w Struts 1.x & Struts 2.x?

7. Date: 18-12-2009. Time: 12.40 pm to 1.40 pm

Consultancy: ABC Consultancy
Bus: from majestic to Richmond Circle—335e)
Landmark: Near Cash Pharmacy

52) What are oop principles?

Abstraction, polymorphism, inheritance, encapsulation

53) While overriding a exception throwing method, does it mandatory that subclass must 

also throw the same exception? No

54) In an application, one task has to be done for every 15 minutes. How can you do it?

55) How do you sort on one property(field) of a class?

Using Comparable Interface by overriding compareTo() method.

8. Date:19-12-2009 Company: HCL Technologies Ltd 

56) If my class is having 5 abstract methods then can I make it as an interface?

Yes

57) What is Log4j? Can I override the logger class?

58) Can I display logging messages on the console?

Yes

59) Which cvs tool are you using? What are the methods that are there?

Commit().

Update()

60) When I don’t want to commit the ResultSet obj content, what to do?

Con.setAutoCommit(“false”);

61) Can I call a procedure from a HB? How? 

Yes

62) Can I use a big query in HB?

63) Difference b/w Checked & Unchecked Exception?

Checked Exceptions deal compile time exception regarding the existence of classes/interfaces

But not syntax errors. 

Ex: ClassNotFoundException---when use a NULL referenced variable to call any 

method/variable.

InterruptedException,---when two or more threads try to share same Resource(wait() and join()) 

NoSuchFieldException ---when we access the undeclared variable

NoSuchMethodException---when we invoke the undeclared method.

InstantiationException---when we try to create object for a abstract/interface

Unchecked Exceptions deal runtime errors.

Ex: ArithmeticException, 

ArrayOutOfBoundsException,

NullPointerException

64) Differenc b/w Exception & Error?

Date: 08-01-2010. Magna consultancy. 

65) What is polymorphism? 

Poymorphism is the capability of an action/method to do different things 

based on an object that it is acting upon. One form, many implementations.

66) What is overloading and overriding? Give one example?

Overloading is the process of re-defining a method for multiple times 

with different Signature.

Overriding is a process of re-defining a super class original version 

in its various derived classes through inheritance.

67) What is encapsulation & abstraction?

Encapsulation is, a technique, used to encapsulate the properties & behaviors of an object.

It focuses on inside-view and solves problems at “implementation side”.

Abstraction refers to the act of representing essential features

without including the background details

68) What is final ? 

class, method, variable.

69) How can you invoke a current class constructor from a method ?

Using “this”.

70) How can you invoke a super class constructor from derived class?

Using “super()”

71) What is “static”? 

method, variable, block, static nested class

72) What is “instanceOf”?

The operator that checks whether given instance is belongs to the given class or not.

73) There are class A & class B. How can I get the members of class A & B?

74) Can I create an interface without methods, constants declarations? 

Yes

75) Can I place try & catch blocks in finally block? 

Yes

76) What are the clone types?

77) How can you make an ArrayList as Synchronized list?

List lobj=Collections.synchronizedArrayList(new ArrayLsit());

Map m=Collections.synchronizedMap(new HashMap());

78) What is Serialization?

Writing the state of an object in to Streams.

79) How can you made the fields of a class to not serialized?

Using the modifier called “transient”

80) What is the use with Generics?

It avoids explicit type casting.

81) What is “Reflection”?

It allows to do Mirror image operations on classes/interfaces to get the internal details.

82) How do you maintain versions in your project? 

Using SVN.

83) What is Junit?

A tool for unit testing.

84) What is logging messages?

SQL

85) What is the difference b/w “order by” and “group by”?

“order by”à used to arrange the data either in ascending or descending order.

“group by”à allows aggregation operations on a column .(having condition also).

86) What are the relations? 

One to one

One to many

Many to one

Many to many.

87) What are the joins? 

Cursors, views, stored procedures….

Hibernate

88) Tell me few Hibernate interfaces? 

i) Configuration(c), 

ii) SessionFactory,

iii) Session, 

iv) Transaction, 

v) Query

89) How do you create “Criteria”?(to do select operations.)

Criteria criteria=session.createCriteria(EmpBean.class);

// select * from Employee where eid between 100 and 200 and firstname in (“raja”,”ramana”));

Condition: 1

criteria=criteria.add(Expression.between(“no”,new Integer(100)),new Integer(200));

Condition: 2

criteria=criteria.add(Expression.in(“fname”,new String []{“raja”,”ramana”} )));

List l=ct.list(); // retrieves more selected records

for(int x=0;x<l.size();x++){

EmpBean emp=(EmpBean) l.get(x);

S.o.p(emp.getNo()+”\t”+emp.getFname()+”\t”+emp.getLname()+”\t”+emp.getEmail());

90) What is Hibernate configuration file?

HB dialect, DB Driver class, Driver class URL, Username, Password. 

91) Why the people using frameworks?

92) What is POJO & POJI model programming?

The programming with no api dependent classes/interfaces

93) What is “Catching “ mechanism? 

To minimize n/w round trips.

“Session” is default and 

“SessionFactory’ explicitly configured.

94) Do you know “restriction” and “expression”?

Expression.between()

Expression.in()

95) Do you know algorithms like increment , sequence, hilo….?

96) What are the different Scopes in JSP?

request, page, session, application

97) How to disable “Cache” ? 

<% resp.setHeader(“cache-control”, ”no-cache”);%> 

(<meta http-equiv=”cache-control” content=”no-cache”>

<%resp.setHeader(“pragma”,”no-cache”);%> //http1.0

OR 

<meta http-equiv=”pragma” content=”no-cache”>)

98) What is default Scope in JSP? 

page

99) How to configure a JavaBean in JSP? 

<jsp:useBean>

100) Do you know UML?

101) Which tools do you used in design documents?

102) What is XML parser, SAX, DOM parsers?

103) Design diagrams?

104) How to configure LOG4J?

105) What are the “validator” files? 

In Struts, validations will be done using validator framework.

Validation.xml – validation will be configured.

validator-rules.xml---validation rulues will be configured.

106) What is “useBean”?

JSP standard tag to configure a Java Bean in JSP.

107) Differences b/w Statement and PreparedStatement apart from performance issue?

Q: What are Statements types?

1) Statement: It is used to execute a “query” only for one time in the entire application execution.

2) PreparedStatement: It is used to execute same “query” for multiple no. of times with the

same/different values. It works with compiled query & allows place holders.

3) CallableStatement: It is used to execute PL/SQL Procedures/functions from the Java appl.

108) How do you configured Spring DAO? 

In contextApplication.xml

109) How to configure “counter” to know no. of users visited the website?

110) How to invoke stored procedures from a Java application? 

Using CallableStatement & prepareStatement();

Date: 23-01-2010. Saturday. CSC India pvt ltd. Domlur Flyover.(333 from majestic)

111)How Java is Platform Independent?

.class file—byte code

112) What is Association and Composition?

113) How can I achieve multiple inheritance in Java without using inheritance?

114) Write the code for a class which implements the Runnable interface?

Public class RunClass implement Runnable{

-------------

-------------

public void run(){

---------

}

Runnable r=new RunClass();

Thread thr=new Thread(r);

thr.start();

115) There are m1(), m2() methods and t1,t2 threads. 

How can t1 execute m1() and t2 executes m2()?

116) What is “join()”? 

When a current thread wants to finish its complete execution and allow the second thread to do

its execution then first thread must invoke this join();

116) How do you make the variables applicable to the whole application in JSP?

117) How do you configure “one to many” association in Hibernate?

<set> and <key> and <one-to-many>

<set name="address"> // child (address table)

<key column="emp_id"/> //primary key of address table

<one-to-many class="EmpAddress"/> //pojo class

</set>

118) What are types of Beans in EJB?

Session Bean---Stateless, Statefull

Entity Bean

MessageDriven Bean

119) Explain the life cycle of EJB?

120) Draw a class diagram for a class?

Class: SampleDemo

Variables: int a, b,c;

Methods: sum(), substract().

Societe Generale: 30-01-2010---Old Madras Road,Benniganhalli ----305 from majestic---

1.00 hour

121) class A{ class B extends A{ class D{

i=10; i=20 ; p s v m(){

printText(){ printText(){ A a=new B();

s.o.p(“from A”); s.o.p(“from B”);

} a.printText(); // from B

} s.o.p( +a.i); } // i=10

122) What is InterruptedException?

When two or more threads try to access same object simultaneously, then this exception

occurs. Join(), wait(), notify() ,notifyAll() throws InterruptedException.

123) What Design patterns do you know?

MVC, Singleton class, Factory , FrontController, DAO class, D.T.O/V.O

124) What an Interface allows in its inside?

Abstract methods, constants, interface.

125) Can I define a class inside an Interface? 

Yes

126) What is HB? What are its files.

It is an ORM tool that is there to develop DB independent persistence logic.

Hibernate-config.xml, Hibernate-mapping.xml, pojo class

127) How to integrate HB with Spring?

The DAO implementation class of spring must extends HibernateDAOSupport and 

implements DAO interface.

128) How to integrate Struts with Spring?

ContextLoaderServlet and

applicationContext.xml configured in struts-config.xml that is there in web.xml

129) What are the differences b/w BeanFactory and ApplicationContext?

BeanFactory (I) container	ApplicationContext (I)
to develop spring core applications.	It is an advanced & extended for BeanFactory. It gives full fledged spring features support like; i) Bean property values can be collected from  “outside properties file”. ii) gives support for Pre-Initialization of Beans. iii) text messages can be collected from  outside property files to give support for i18n. iv) allows to work with EventHandling through Listeners.

Pre-initialization: creating Bean class objects & performing Dependency Injection on 

Bean properties at the time of container activation.

130) What is the interface implemented by HashMap and Hashtable?

Map (i)

131) Can you unit test a “private method”?

132) What are ServletListeners?

Source obj	Event	Listener	EventHandling methods (public void
ServletRequest ServletContext HttpSession	ServletRequestEvent(sre) ServletContextEvent(sce) HttpSessionEvent (hse)	ServletRequestListener ServletContextListener HttpSessionListener	requestInitialized(sre) requestDestroyed(sre) contextInitialized(sce) contextDestroyed(sce) sessionCreated(hse) sessionDestroyed(hse)

From Servlet 2.4 onwards, EventHandling is allowed on special objects of webapplication

like ServletContext, ServletRequest, HttpSession objects.

ServletRequest: 

By doing EventHandling on ServletRequest object, we can keep track of 

each “request” object creation time & destruction time. Based on this, we can 

find out “request processing time”.

HttpSession: 

By performing EventHandling on HttpSession object, we can find out

“session” object creation time & destruction time. Based on this, we can 

know the time taken by the each user to work with “session”.

Procedure to configure Listeners with webapplication

1) Develop a Java class implementing appropriate “Listener” 

& place it in WEB-INF/classes folder.

2) Configure that Listener class name in web.xml by using <listener-class>

Dell Perot Systems-----iGATE,WhiteField,Industrial Area

133) What is a Session?

Session: It is a set of related & continuous requests given by a client to a web application.

Ex: SignIn to SignOut in any Mail Systems Application like Gmail, Ymail etc…

134) How do you maintain client data at client side?

Cookies

135) What are the methods with Serializable interface? 

No methods are there in Serializable Interface as a Marker/Tagged Interface.

Ex: Serializable, Cloneable, Remote, SingleThreadModel

136) What are the sorting methods are there in Java?

137) Write the code for them?

138) What are the Http request methods? 

GET,POST

139) Difference b/w GET and POST methods?

GET	POST
1) It is a default Http request method 2) Query string is visible in Browser address bar hence no data Secrecy. 3) It allows to send limited amount of  data(1kb) 4) It is not suitable for File uploading. 5) It is not suitable for sending Enscripted data. 6) It shows Idempotent behaviour. 7) Use either doGet(-,-) or service(-,-) to process this.	Not a default method. It gives data Secrecy. Unlimited amount of data. Suitable for File uploading. Suitable. Non-Idempotent. Use either doPost(-,-) or service(-,-)

140) What is Idempotent behavior?

It is the behavior like processing the multiple same requests from the same web page.

141) How the POST is not having Idempotent behavoiur?

142) How the JSP code is converting into Servlet code? 

JSP parser/Engine/compiler

143) What is Servlet life-cycle?

1. If an instance of the servlet does not exist, the Web container

a. Loads the servlet class.

b. Creates an instance of the servlet class.

c. Initializes the servlet instance by calling the init method. 

2. Invokes the service method, passing a request and response object. 

3. If the container needs to remove the servlet, it finalizes the servlet by calling 

the servlet's destroy method.

144) Can I Implement Serializable when I don’t want to save the object in persistence stores? 

If NetWork is there then YES else NO.

145) What is “reflection api”?

import java.lang.reflection;

Reflection API based applications: 

are capable of gathering “internal details about a Java class/ interface

by performing Mirror Image Operations on that class/interface.

146) What are the SessionTracking Techniques?

Session Tracking: It is a technique by which the client data can be remembered across 

the multiple requests given by a client during a Session.

1) Hidden Form Fields

2) Http Cookies

3) HttpSession with Cookies

4) HttpSession with URL-rewriting.(best)

147) How to handle multiple submit buttons in a HTML form?

<input type=”submit” name=”s1” value=”add”> </th>

<input type=”submit” name=”s1” value=”delete”> </th>

<input type=”submit” name=”s1” value=”modify”> </th>

Code for accessing the above data in Servlet.

String cap=request.getParameter(“s1”);

if(cap.equals(“add”)) {

---------- }

elseif(cap.equals(“delete”)) {

------------- }

else(cap.equals(“modify”)) {

------------ }

HoneyWell---from Banshankari 500L, Intel Stop, Dhevarabesinahalli---2.00pm—15 mints

1) What you write to open a window?

Window.open(); in Javascript

<a href="javascript:;" onClick="mm_openbrwindow('Mypage.html','','width=800, height=600, scrollbars=no')">MyPage</a>

        newwindow=window.open(url,'name','height=500,width=400,left=100,

  top=100,resizable=yes,scrollbars=yes,toolbar=yes,status=yes');

148) Do you know CSS? What can I do with CSS?

CSS is a style language that defines layout of HTML documents. For example, CSS covers fonts, colours, margins, lines, height, width, background images, advanced positions and many other things

149)What is the difference between CSS and HTML?

HTML is used to structure content. CSS is used for formatting structured content.

150) What are the uses with Hibernate?

i) It allows to develop DB independent query language like HQL.

ii) It supports POJO/POJI model programming.

iii) Any Java/J2EE can access HB persistence logic.

iv) It supports to call all Procedures & Functions of PL/SQL programming.

v) The result after “SELECT” operation, by default, is “Serializable”.

151) What are the differences b/w Servlet and JSP?

For every time we modifing the servlet , we should re-deploy the servlet. 

Its very big headache.

Manually written servlets are somewhat faster than JSPs.

JSP:

i) No need of Recompilation & Reloading when we do modifications in a JSP page.

ii) We need not to Configure a JSP in a “web.xml”.

iii) It is providing huge amount of Implicit Objects support.

iv) Since Html & Java code are separated hence no disturbance while changing logic.

v) It is providing implicit XML Exception Handling support.

152) How to connect with DB?

Class.forName(“oracle.jdbc.driver.OracleDriver”);

Connection con=DriverManager.getConnection(“jdbc:oracle:thin:@localhost:1506”,

”logicalDBname”,”username”,”password”);

Statement st=con.createStatement();

// ResultSet rs=st.execute(“select query”); (or)

// int x=st.executeUpdate(“Non-select query”);

153) Code for DataSource?

Context ct=new InitialContext();

Object obj=ct.lookUp(“ JNDI name of dataSource reference”);

DataSource ds=(DataSource)obj;

Connecton con=ds.getConnection();

Statement st=con.createStatement();

--------------------

con.close();

154) What is the return type of “executeUpdate()” ?

It is used to execute “Non-Select queries” and 

whose return type is “int”.

155) What is “OUTER join”? 

It gives both matching and non-matching rows.

156) What is an Application Server?

i) It allows to deploy all types of Java applications like web, distributed,enterpraise

applications.

ii) It contains both web and ejb containers.

iii) It gives more implicit middleware support like Tx management, Security, Connection 

pooling..

Adea Technologies Pvt Ltd, BommanaHalli; Hosur Road; majestic---356;06-02-2010

157) How to know the no. of dynamically generated objects of a class?

Take a Static count variable, pass this to a” Parameterized Constructor” and keep the 

increment operation inside it. 

158) Can you write the flow for ATM ?

159) What is Synchronization?

The process of allowing only one thread among n no. of threads into a Sharable Resource

to perform “Read” & “Write” operations.

160) What are the primitives?

byte, int, short, long, float, double, char, booleanàlocal variables.

161) What happens when we store primitives to Collections?

162) What are the Wrapper class objects?

The primitives are not allowed to store inside the collections. So, they will be converted into

Wrapper class objects using their respective wrapper classes.

163) What is the difference between “Apache Server” & “Tomcat Server”?

Apache/ Apache HTTP Server, is an established standard in the online distribution of website services, which gave the initial boost for the expansion of the W.W.W.

. It is an open-source web server platform, which guarantees the online availability of the majority of the websites active today.

The server is aimed at serving a great deal of widely popular modern web platforms/operating systems such as Unix, Windows, Linux, Solaris, Novell NetWare, FreeBSD, Mac OS X, Microsoft Windows, OS/2, etc.

164) What is an ApplicationServer? 

165) Why do we require Application Server instead of Web Server?

166) An application is having “images”. Which Server is preferable?

167) What is Autoboxing?

Autoboxing is an implicit automatic conversion from Primitives to Wrapper class objects.

Ex: float p_float=0.5f;------à Float 0_float=new Float(p_float); will done implicitely.

Unboxing is an implicit automatic conversion from Wrapper class objects to Primitives.

Ex: Float o_float=0.2f;----à float p_float=o_float;

Tech Mahendra, opposite to Christ University, Hosur main Road.06-02-2010

168)What are new features of jdk1.5? 

Generics, Enhanced For loop, Autoboxing/Unboxing, Static import, Annotations.

169) Write the code for “Enhanced for loop”?

int[] integers={1,2,3,4,5};

for(int item:integers){

S.o.p(item);

}

170) What is an Annotation in JDK1.5? 

Sun has recently released Annotation Processing Tool (apt) along with beta2 of JDK1.5.

This tool greatly helps in using the annotations feature that is introduced in JDK1.5

Annotations can be at package level, class level, field level, method level and even at

local variable level.

171) I have a HashMap. I want to get the keys & values in a set. Can you write the code?

HashMap<Integer,String> hm=new HashMap<String,String>();

hm.put(1,”ram”);

hm.put(2,”sri”);

Set s=hm.keySet();

for(Integer keys:s){

for(String values:hm.get(s)){

S.o.p(values+” ”+keys);

}

172) Which algorithm is used by JVM while running Garbage Collection?

Mark-in-sweep.

173) Can an application has multiple Struts-config.xml?

Yes…one for each module

174) Where do you configure Struts-config.xml in an application?

Web.xml

175) How do you Unit test in Spring environment?

176) How do you disable all the JavaScripts of pages in an application?

177) Why there are Directive and Action tags in JSP?

Directive tags: perform Global operations on a page like 

i) importing packages, 

ii) working with tag-library

iii) including other JSPs content and etc.,.

ex: page, include, taglib

Action tags: 

are there to perform actions during request-processing/execution phase of JSP.

Ex: include, forward,useBean, setProperty, getProperty, param, plugin. 

178) What does Tomcat Support?

War file

179) What is dialect?

Using dialect, Hibernate knows the type of DB & its version to which it will connected.

180) How do you map HB Pojo class with Table?

<hibernate-mapping default-cascade="none" default-access="property" default-lazy="true"

auto-import="true">

<class name="CustomerOrder" table="CustomerOrder" mutable="true" polymorphism="implicit" dynamic-update="false" dynamic-insert="false" select-before-update="false" optimistic-lock="version">

<composite-id name="orderId" class="OrderId" mapped="false" unsaved-value="undefined">

<key-property name="customerId" column="customer_id" />

<key-property name="orderTime" column="order_time" />

</composite-id>

<property name="orderDescription" unique="false" optimistic-lock="true" lazy="false" generated="never" />

</class>

</hibernate-mapping>

181) In HashMap, how can I locate a particular key?

Hm.containsKey(“3”); Hm.containsValue(“key”);

182) Difference b/w SVN(Sub VersioN) & VSS (Visual Source Safe--microsoft)?

Usually team members do all of their work separately, in their own working copies and need to share their work. This is done via a Subversion repository. Syncro SVN Client supports the versions 1.3, 1.4, 1.5 and 1.6 of the SVN repository format

1. Expansion. The number of programmers doubled and we didn't want to fork out for the extra VSS licenses
2. Bugs. VSS is good at maintaining the latest version of a file, but histories often got corrupted.
3. More bugs. The checking/recovery tools were useless as they started crashing when the database got very large.

183) What is Servlet Chaining?

Servlet Chaining is a method of processing the request using multiple servlets as a chain.

184) What is the use of DyanaActionForm?

It allows Declarative data population that avoids recompilation.

185) prototype of execute(-,-,-,-)?

public ActionForward execute(ActionMapping am, 

ActionForm af, 

HttpServletRequest req,

HttpServletResponse resp)

186) Difference b/w ActionForm, DynaActionForm and DynaValidatorForm?

All three are JavaBean Classes that can maintain the session state for web application. 

The ActionForm object is automatically populated on the server side with data 

entered from a form on the client side.

An ActionForm/DynaValidateForm can have getter(),Setter(), reset() and the validate() methods that can be defined in our ActionForm or in Action class itself. 

* If any changes are made to the properties, code need to be recompiled.

Here comes the DynaActionForm to rescue. It allows properites to be specified in Struts-cofig.xml file there by avoiding the recompilation of the code.

Also there is no need to have a Form Bean for every page that had getter and 

setter method for each of the field on the page.

This is how it can be declared in struts config file:

<form-beans>

<form-bean name="employeeForm"

type="org.apache.struts.action.DynaActionForm">

<form-property name="fname" type="java.lang.String"/>

</form-bean>

</form-beans>

187) How the DispatchAction knows, when it is pointed by multiple JSPs, 

which jsp request execute which DispatchAction method to process the request by 

executing the B.logic?

JSP sends the “method name” along with the request as 

additional request parameter to DispatchAction.

function=insert, update, delete.(methods in OurAction)

Take a “parameter” attribute that represents all the methods of DispathAction class that 

configured in Stuts-Config.xml using <action-mappings>.

Take the different JSP forms where property=”parameter value” and value=”method-name”

under the hidden tag.(<input name=”” type=”” value=” ”>)

<action-mappings>

<action path=”/controller1” 

name=bean

type=”OurAction” //name of the DispathAction

parameter=function scope=”request”/>

Add.jsp: <html: hidden property=”function” value=”insert”>

Modify.jsp: <html: hidden property=”function” value=”update”>

Delete.jsp: <html: hidden property=”function” value=”delete”>

188) Types of Action classes in Struts?(8)

Actionà to execute B.logic by keeping in execute() or to place request processing logic.

ForwardActionà It is there to forward/transfer the control from one web resource to another

through the controller.(i.e.,according to MVC principle, any two JSPs

should not communicate directly. Use ForwardAction that will configured in

Struts-config.xml)

IncludeActionà It is there to include response of JSP to another through controller.

DispatchActionà It groups the related Action classes into single “Action” class and allows

multiple user defined methods as execute() to differentiate the B.logic.

(so that multiple JSPs giving request to single DispatchAction, can be linked 

with different methods available.)

MappingDispatchActionà 

LookupActionà

SwitchActionà

LocaleActionà

189) ACID Operations

Atomicity:

The process of combining invisible & individual operations into a single unit.

Consistency: 

It is a process where the rules applied on DB may be violated during Tx 

but no rule is violated at the end of a Tx. 

Ex: Account table—balance field –no negative bal

Isolation:

The process of applying locks on a DB table at various levels to avoid data corruption 

when multiple users are allowed concurrently/simultaneously.

Durability:

The process of bringing the DB s/w original state using the log & back up files 

when it was crashed/corrupted.

Keane India Ltd, Basavanagudi, South End Circle. Banshankari---

190) What is Expression tag in JSP?

It is used to 

i) evaluate a Java expression & sends that result to Browser-window. <%=a+b;%>

ii) display the variable values on the Browser-window. <% int a=10;%> <% =a %>

iii) call both pre-defined & user-defined methods.

<%=sum(10,20)%> , <%=”raja”.length()%>

iv) instantiates java classes & to display the default data of the object.

date and time is:<%=new java.util.Date();%>

192) What is “isThreadSafe=true” in JSP? 

It makes the equivalent servlet as thread safe.

The “JSP equivalent Servlet” will implement SingleTreadModel(I) implicitely.

193) Why there is Object class?

To provides the default, common implemented code for every java class/interface.

Methods available in Object class are:

int hashCode(), 

boolean equals(Object obj), 

void finalize() throws Throwable, 

String toString(), 

Object clone() throws CloneNotSupportedException,

final Class getClass()

final void wait()throws InterruptedException

final void notify()throws InterruptedException

final void notifyAll()throws InterruptedException

194) Why hashcode(),equals()…are there in Object class?

195) What is Self Join? A table joins with itself.

196) sum(): select sum(salarycolumn) from tablename group by salarycolumn;--groups the same 

salaries into different groups.

select sum(salarycolumn) from tablename;-à gives total sum of salary column

197) What is Setter and Constructor injection?

à Setter Injection:

It is a process of injecting/assigning the dependent values to the Bean properties

by the spring container using Bean class setXXX(-) methods.

Note: In Spring Config.xml:

<property name=”age ”>

<value> 20</value> 

</property>

à Constructor Injection: 

It is a process of assigning/injecting the dependent values to the Bean properties

by the spring container using “parameterized Constructors”.

Note: In Spring config.xml:

<constructor-arg> 

<value>ramu</value> 

</constructor-arg>

198) Can we use Setter Injection when we use private Constructor?

No

199) What is the problem with Autoboxing ?

200) Serializable code?

FileOutputStream fos=new FileOutputStream(“file name”); ---file opened

ObjectOutputStream oos=new Object OutputStream(fos); --Object takes file ref

UserDefSerCls uds=new UserDefSerCls(,” ”,);

Oos.writeObject(uds);

Oos.close();

201) What is “inverse=true” in hbm file?

The Association is bi-directional.

202) What is an Nested class?

The class defined in another class.

Nested class Types:

i) static nested class

ii) non-static nested class (inner class)

Nested class Use :

i) They can lead to more readable & maintainable code.

ii) It increases encapsulation.

iii) It is a way of logically grouping classes that are only used in one place.

Inner-class object creation:

OuterClass.InnerClass innerObject=outerObject.new InnerClass().

Anonymous Class: a name-less local class .

When to use: 

i) when a class has a short body.

ii) only one instance of the class is needed.

203) How to establish many to many association?

Declare one column as primary key in the Parent table.

Declare one column as primary key in the child table.

Take another table where above two primary keys will be declared as foreign keys.

204) Can I develop a spring application without hbm file.

Yes, by using “Annotation”

205) Can I develop a spring application without spring config.xml?

Yes, by using Properties file.

206) What is distributed transaction?

The transaction where two databases are used for a project.

207) Differences b/w procedure & function?

Procedure	Function
1) may or may not return value. 2) may returns one or many values(max.1024) 3) result is gathered only through OUT parameters.	must returns a value. Must return exactly one value through OUT parameters & return value.

208) Difference b/w Primary and Unique key?

Primary key: 

Only one Primary key constraint can be applied to a table.

Primary key column won’t allow duplicates.

Primary key column won’t allow NULL.

Unique key: one or many Unique key constraint can be applied to one table.

It allows duplicates.

It allows NULL.

209) Is the Servlet thread-Safe by default? 

No, the servlet by default is not Thread safe. To achieve this, the servlet must implements 

SingleThreadModel interface OR synchronize the service().

210) Explain Joins?

Purpose : to bind data together, across tables, without repeating all of the data in every table.

JOIN: Return rows when there is at least one match in both tables

LEFT OUTER JOIN: Return all rows from the left table, even if there are no matches in the right table

RIGHT OUTER JOIN: Return all rows from the right table, even if there are no matches in the left table

FULL OUTER JOIN: Return rows when there is a match in one of the tables

SELF JOIN :

EQUI/INNER JOIN:

211) How do you maintain bug tracking in your project? 

Using JIIRA tool.

212) What tool are you using to write hundreds of fields for your project?

213) What code styles are you following in IDE?

214) Procedure to work with PreparedStatement in a Java application.

1). Prepare a query having “positional/place” holders/”in parameters”.ie.(?,?,?)

2). Send the query to DB s/w, make the query as “pre-compiled query” & represent 

it through “PreparedStatement”.

3). Set the values for place-holders using “setXXX(-,-)”.

4). Execute the query.

5). To execute the same query for multiple no. of times with same/different values,

repeat steps 3 & 4 for multiple times.

6). Close PreparedStatement object.

à Pre-compiled query: a query that goes to DB & becomes 

compiled-query without values, and also resides on DB.

It reduces “Network traffic” b/w Java appl & DB s/w.

215) How to display data from the table in HB?

SessionFactory sf = new Configuration().configure().buildSessionFactory();

Session session = sf.openSession();

Transaction t = session.beginTransaction();

Student st = new Student(); //pojo

//Displaying data from Student table using HQL 

Query qry = session.createQuery("from Student");

List lst = qry.list(); // data saves into List with no restrictions

//Restrcting data based on age condition

Criteria ct = session.createCriteria(Student.class); 

ct.add(Restrictions.ge("studentAge", 20));

List lt = ct.list();

Iterator<Student> itr = lt.iterator(); // displays all records

System.out.println("Student no: \t Name : \t Age");

while (itr.hasNext()) {

Student student = itr.next();

System.out.println(student.getStudentId()+"\t"+

student.getStudentName()+"\t"+student.getStudentAge());

}

216) How to insert one record into a Table (single row insertion)

student.setStudentName("sridhar");

student.setStudentAge(28);

session.save(student);

217) How to update existing a table record?

student.setStudentId(5); //primary key val

student.setStudentName("sridhar");

student.setStudentAge(28);

session.saveOrUpdate(st);

218) How to delete a table record from HB session obj?

session.load(student, new Integer(1)); // load(Student.class, primarykey)

session.delete(student);

219) What are the Escape characters in JSP?

220) How many ways are there to invoke a Servlet object.

221) What is the difference b/w Filter and Servlet?

222) What is syntax for doFilter()?

223) How to convert list into HashMap?

224) Give me one example for Detached state of an object in HB?

225) What is Collection use?

They allow to store heterogeneous objects.

226) What is the implementation class of SessionFactory? 

LocalSessionFactoryBean

227) How do you configure one to many and many to many for an single Hb application?

226) What is Bi-directional and Uni-directional in HB?

inverse=”true”-àmeans bi-directional association.

Inverse=”false”àmeans uni -directional assoiciation

227) What is custom Servlet?

The servlet that extending pre-defined Servlet (ie HttpServlet/GenericServlet/Servlet)

228) How do you get key when value is available from HashMap?

HashMap<Integer,String> hm=new HashMap<Integer,String>();

hm.put(1,”ram”);

hm.put(2,”sri”);

hm.put(3,”mano”);

Set<Entry<Integer,String>> set=hm.entrySet();

for(Map.Entry<Integer,String> me:set){

if(me.getValue()==”ram”)

s.o.p(“the key value is:”+key):}

OR

Set s=hm.entrySet();

Iterator itr=s.iterator();

while(itr.hasNext()){

Object mobj=itr.next();

Map.Entry me=(Map.Entry)mobj;

if(me.getValue()=="anu")

System.out.println("key is:"+me.getKey() );}

229) How to do Pagination?

230) Write the code for displaying the data from DB in Struts?

231) Signature of “validate()”?

Public ActionErrors validator(ActionMapping am, HttpServletRequest req)

234) Write the code for CallableStatement?

Don’t know….

That’s IT Folks…………….