important interview quitions

7/31/2019 Important Interview Quitions

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9 What is API document?

A) API document is a HTML file that contains description of all the features of

software, a product or a technology. It works has a heap file.

API document like user documentation. To create API doc we need java doc compiler.Function code is available in header file.

10 What is the difference between #include and import?

A) #include makes a C or C++ compiler to go to standard library and copy the entire

header file code in to a C/C++ programs. So the program size increases unnecessarily

wasting memory & processor time.

Import statement makes the JVM to go to the java library, execute the code &

substitute the result in to the java program. Thats JVM doesnt copy any code. So

import is more efficient than #include

11 What is JRE?A) JRE means java run time environment.

JRE=JVM + java library

JRE is available in JDK1.5. It represents entire software.

12 What are command line arguments?

A) The values passed to main method at the time of running a program or called

command line arguments. Its stores in array.

13 What is the distance between a float and double?

A). Float represent up to 7 digits accurately after decimal point.

Double represent up to 15 digits accurately after decimal point.

14 What is uni code?

A) Uni code is a standard to include the alphabet from all human languages in java.

Uni code system uses 2 bytes to represent a character.

15 What is the value of the following expression? Given a=7? ++a * a++?

A) A) 49 B) 64 C) 72 D) none of these

16 What is the difference between >> & >>>?

A) >> shift the bits 2 words right & properties the sign bit (0 represent +ve 1 represent

ve sign)>>> also shift the bits 2 words right bit. It does not protect sign bit. It always fills the

sign bit with 0.That reason it is called zero-fill right shift.

17 Why goto statement are not available in java?

A) 1) goto statements lead to confusion for a programmer.

2) goto statement from infinite loops which are draw backs in a program.

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3) the documentation of the program will become difficult with more gotos are

used. Documentation means preserving a copy of the program. Algorithm means a

step of logic.

4) goto statements are not part of structured programming. Because of above

reasons the goto statements are eliminates of java.

18 What is the difference between System.exit(0) and System.exit(1)?

A) System.exit(0) represents normal termination.

System.exit(1) represents termination due to an error.

19 What is difference between System.out & Sytem.err?

A) System.out is useful to display general messages.

System.err is used to display error messages. Stream is one of the io device.

20 What are command line arguments?

A) Command line arguments are values passed to main method from system prompt.

JVM allots memory in run time.

args.length Size of arguments.

21 What is hash code?

A) It is a unique identification number that is allotted by JVM to the objects. This

number is also called reference number.

So the out put is not same. == is only compare reference numbers

22 What is the difference between == to and equals method while comparing the

strings?

A) == operator compares only the reference of string objects.

Equals method compares the contents of the string objects. Hence the equals method

gives reliable results.

23 What is string constant pool?

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A) It is separate block of memory where the string objects are stored.

If(s1==s2)

o/p: - equal. Because JVM does not waste memory.

24 What is the difference between the following statements?

a) String s=Hello;

b) String s=new String(Hello);A) When the first statement is executed JVM searches for the same object in the string

constant pool. If the same object is found there then JVM will create another reference

to the same object, if the same object not found JVM creates another object & stores it

into string constant pool.

When the second statement is executed JVM always create a new object

without searching in the string constant pool.

25 What is the difference between a string & StringBuffer?

A) String objects are immutable. StringBuffer objects are mutable.

The methods which directly manipulate the data or not available in string class. Such

methods are available in StringBuffer class.

26 What is software requirement specification (SRS)?

A) SRS is a document that contains client requirements and strategies to fulfill those

requirements. SRS is prepared by project leader.

27 What is software design specification(SDS)?

A) SDS is a document that contains I/O screens, PSUDO code, DFDs dataflow

diagrams, Black end data bases etc.., it is prepared by module leader.

28 What is the difference between object oriented programming language & object

based programming language?

A) Object oriented programming languages follow all the features of OOPs.

EX: - C++, Java, Small Talk, Simula 67

Object based programming language follow all the features of OOPs, expect

inheritance.

EX: - Java script, VB script.

29 What is the default constructor & parameterized constructor?

A) Default constructor is used to initialize every object with same data.

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Parameterized constructor is used to initialize each object with different data.

30 What is constructor overloading?

A) Writing 2 or more constructors with same name with difference in the parameter is

called constructor overloading.

31 What is different between instance variables and static variables?

A) 1) Instance variables are a variable whose separate copy is available to each object

of the class. So any modification to the instance variable in one object will not modify

the other objects.

Static variables are variables whose single copy is shared by all the objects of the

class. If the static variable value is modified. It affects the value in all the objects.

2) Where instance variables & static variables are stored

Instance variables are created on heap.

Static variables are stored on method area.

32 In how many ways can you create on object in java?

A) Ways of creating on object: -

1) Using new operator

Employee obj=new Employee( );

2) using factory method

NumberFormat obj=new NumberFormat.getInstance( );

3) using newInstance( ) method

Class c=Class.forName(Employee);

For name method will store employee that class name in an object

This is represented by c.

4) Using cloning( )Cloning means creating bitwise exact copy of an existing object.

33 What is object graph?

A) A graph connecting several objects is called object graph.

34 What is the advantage of inheritance?

A) In inheritance a programmer can re use already developed code. Because of these

developing new programs will become easy. This increases productivity of

programmer & hence the over all productivity of the company or organization will

also increase.

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35 What is method signature?

A) Method name & its parameters is called method signature.

36 What is the difference between method over loading & method overriding?

A) Method over loading: - Writing 2 or more methods with the same name, but with adifference in the method signatures is called method over loading. In method over

loading JVM understand in the method is called depending upon the difference in the

method signature.

Method overriding: - writing 2 or more methods in super & sub classes with same

name & same signatures is called method overriding. In method overriding JVM

executes a method depending on the data type of the object.

Achieving method overloading & method overriding using instance methods is an

example of dynamic polymorphism.

37 What is final?

A) 1) final is used to declare ConstanceEx: - final double PI 3.14159

2) final key word is used to prevent inheritance.

Ex: - final class A

class B extends A // invalid

38 What is difference between primitive & advanced data types?

A) 1) Casting can be used to convert one primitive data type in to another primitive

data type.

2) Casting can be used to convert one advanced data type into another advanced data

type.

3) Casting can not be used to convert a primitive data type into an advanced data typeand vice versa (means reverse also).

For this purpose we can use wrapper classes.

39 What is generalization & specialization?

A) Moving back from sub class to super class is called generalization. Casting a sub

class type into a super class is called a up casting or widening.

Coming down from super class to sub class is called specialization. Casting a

super class type into sub class type is called narrowing or down casting.

40 What is widening & narrowing?

A) Widening: - Casting a lower data type into a higher data type is called widening. Inwidening no digits or precision are lost. Casting a sub class type into a super class is

called an up casting or widening. In widening we can access super class methods. In

widening we can access sub class methods. In widening us can not access sub class

methods unless the override super class methods.

Narrowing: - Converting a higher data type into lower type is called narrowing. In

narrowing precision or digits are lost. This is called explicit casting. Casting a super

class type into sub class type is called narrowing or down casting. Narrowing using

super class object can not access either super class methods or sub class methods.

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Narrowing using sub class object will make the programmer to access are the

members of super class as well as sub class.

41 How can enforce discipline in the programmers to implement only your class

features?

A) By writing an abstract class or an interface I can enforce.42 What is the difference between an abstract class & interfaces?

A) A programmer writes an abstract class when there are common features shared by

the all the objects.

A programmer creates an interface when every feature is implemented

differently for different objects.

A programmer prefers to create an interface when he wants to leave

implementation for third party venders.

43 How much memory is taken by class twos object?

1) 4 b 2) 8 b 3) >8 b 4) 8 b because

44 Why multiple inheritances are not supported in java?

A) 1) Multiple inheritance leads to confusion for a programmer. Operator overloading, multiple inheritances are not available in java.

2) If the programmer wants we can achieve multiple inheritance using

interfaces.

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class D extends A,B,C // invalid

class D implements A,B,C // valid

Here A,B,C are not classes only interfaces. So it is not multiple

inheritances. This is way of multiple inheritances indirectly.

3) A programmer can achieve multiple inheritances by using single

inheritance repeatedly.Because the above reasons the direct multiple inheritances is not available in java.

45 What is java archair file?

A) Jar file is a compressed version of several. Class or. Java files. A jar file created

using jar utility provided by sun micro systems.

46 What is class path?

A) Class path is an operating system variable. That stores active directory path.

To sea the class path

D:\ psr> echo %classpath%

Display content of class path

.\;C:\Program Files\Java\jdk1.5.0_07\jre\lib\rt.jar;d:\psr;To set the class path to the package directory.

D:\psr> set classpath=d:\psr\pskr;.;%classpath%

Compile the above program & run it.

47 What is checked exception?

A) The exception will occur during compilation & are executed by the java compiler

are called checked exception. The exception which are detected at runtime by the JVM

are called unchecked exceptions or run time errors.

48 All exceptions are subclasses of which class?

A) Exception class.

49 What is throwable?

A) Throwable is a class that represents is errors & exceptions in java

50 What is Exception?

A) Any abnormal event in the program is called an exception.

51 What is the difference between throws & throw?

A) throws is used to throw out of an exception without handling it.

throw is used to create an exception & throwing it & handle it.

52 Which of the wrapper classes does not a constructor with string parameter? (or)

Which of the wrapper classes contains only one constructor?

A) Character

53 What is collection framework?

A) It is a class library to handle group of objects. It is implemented in java.util

package.

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Collection object does not store copies of other objects. It stores only references of

other objects.

Advanced java1 What is load factor?

A) Load factor determines at what point the initial capacity of a hash table or a hash

map will be double. Load factor is 0.75 of hash table.

For a hash table initial capacity x load factor = 11x0.75=8 approximately. It

means after storing 8th key value pair will be doubled=22.

2 What is the difference between Vector & array list?

A) 1) From the API perspective, the two classes are same.

2) Vector is synchronized & array list is not synchronized.

Note: - We can make array list also synchronized by using:

Collections. synchronizedList(new ArrayList( ));

3) Internally both are hold onto their contents using an array. A vector by default

increments its size by doubling it, & on array list increases its size by 50%.

4) Both are good for retrieving elements from a specific position in the container or

for adding & removing elements from the end of the container. All of these

operations can be performed in constant time---0(1), but adding & removing

elements in the middle takes more time. So in this case a linked list is better.

3 What is the difference between hash table & hash map?

A) 1) Hash table is a synchronized, where as hash map is not.

Note: - We can make hash map also synchronized by using:

Collections. synchronizedList(new HashMap( ));

2) Hash map allows null values as keys & values, where as hash table does not.

3) That iterator in the hash map is fail-safe, while enumerator for the hash table

isnt.

4 What is the difference between a set & list?

A) 1) Sets represent collection of elements. Lists represent ordered

Collection of elements (also called sequence).

2) Sets will not allow duplicates values. Lists will allow.

3) Accessing elements by their index is possible in lists.

4) Sets will not allow null elements, lists allow null elements.

5 Which is the thread internally running in every java program?

A) Main thread.

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6 What is the difference between thread & process?

A) Process is a heavy weight, means it takes more memory & more processor time. A

thread is a light weight process, means it takes less memory & less processor time.

7 How can you stop in the thread in the middle?

A) 1) Declare the boolean type of variable & initialize at falseboolean x=flase;

2) If the variable value is true , x return from the method.

If(x) return;

3) To stoop the thread store true in to the variable

System.in.read( ); obj.x=true;

8 What is the difference between extends Thread & implements runnable?

A) Functionally both are same. If we use extends Thread then there is no scope to

extend another class. Multiple inheritances are not supported in java.

class MyClass extends Thread,Frame // invalid

But if we write implements Runnable then there is still scope to extends some other

class.class MyClass implements Thread,Frame // valid

So implements Runnable is more advantage of than extends.

9 What is thread life cycle?

A) A thread is crated by creating on object to thread class. The thread is executed by

using start method. When the thread is started it goes into runnable state. Yield

method passes the thread but still the thread will be in runnable state.

The thread wills coming to not runnable state, when sleep or wait methods are

used or if it is blocked on I/O the thread is not runnable state. From this state, it comes

into runnable state after some time. A thread will die when it comes out of run

method.The above states from the birth of a thread till its death are called life cycle of a

thread.

10 What is an adapter class?

A) An adapter class is an implementation class of a listener interface where all the

methods will have empty body. For example window adapter is an adapter class

window listener class.

class Myclass extends WindowAdapter {

public void windowClosing(WindowEvent e)

{

System.exit(0);}

}

11 What is anonymous (means 1) inner class?

A) It is an inner class whose name is not maintained & for which only one object is

created to MyClass

f.addWindowListener(new WindowAdapter()

{

public void windowClosing(WindowEvent e)

{

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System.exit(0);

}

});

12 What is the default layout manager in a frame?

A) Border layout

13 What is the default layout manager in applets?

A) Flow layout

14 Repaint methods calls which method?

A) Update method it will call internally.

INET

1)What is a singleton class?How do you writer it? Tell examples ?

A class which must create only one object (ie. One instance) irrespective of any

number of object creations based on that class.

Steps to develop single ton class:-1.Create a Private construcor, so that outside class can not access this constructor.

And declare a private static reference of same class

2.Write a public Factory method which creates an object. Assign this object to

private static Reference and return the object

Sample Code:-

class SingleTon

{

private static SingleTon st=null;

private SingleTon( )

{

System.out.println(\nIn constructor);}

public static SingleTon stfactory()

{

if(st==null)

st=new SingleTon( );\

return st;

}

}

2) What is the difference between using HttpSeassion & a Stateful Session bean? Why

can't HttpSessionn be used instead of of Session bean?

HttpSession is used to maintain the state of a client in webservers which are based onHttp protocol. Where as Stateful Session bean is a type of bean which can also

maintain the state of the client in Application servers based on RMI-IIOP

3)Question on Seggregation in UML?

4)What is Temporary Servlet ?

When we sent a request to access a JSP, servlet container internally creates a

'servlet' & executes it. This servlet is called as 'Temporary servlet'. In general this

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servlet will be deleted immediately to create & execute a servlet base on a JSP we

can used following command.

Java weblogic.jspckeepgenerated *.jsp

5) Generally Servlets are used for complete HTML generation. If you want to

generate partial HTML's that include some static text (this should not be hardcoded in servlets)

as well as some dynamic text, what method do you use?

Using 'RequestDispather.include(xx.html) in the servlet code we can mix the

partial static HTDirectoryML page.

Ex:- RequestDispatcher rd=ServletContext.getRequestDispatcher(xx.html);

rd.include(request,response);

6)Difference between and tags ? action tag redirect the servlet Request and Servlet Response to

another resource specified in the tag. The path of the resource is 'relative path'. The

output generated by current JSP will be discarded.

action tag process the resource as part of the current jsp. It include

the o/p generated by resource, which is specified in the Tag to the current JSP

*) In both the cases single Request proceses multiple resources.

7) Purpose of tag:

It is used to generate client broser specified HTML tags which results in

download of the java plugin sofware. And the execution of the applet or java

Bean component that is specified in the tag.

8) The time between Command Execution and Response is called?

9)Which method is called first each time a Servlet is invoked?

When the servlet obj is not created init( ) method will be called. It servlet obje is

already exists 'service() method will be called.

10)Tell about EJB tranctions and how to manage them ?

11) Why DB connections are not written directly in JSP's?

The main purpose of JSP is to seperate the business logic & presentation logic. DB

connections deal with pure java code. If write this kind of code in JSP, servlet

container converts the JSP to servlet using JSP compiler which is the time consuming

process so this is better to write code wich deals with DB connections, Authentication

and Authorization etc. in the java bean and use the tag to perform the

action

12)What is key diffrence between using a and

HttpServletResponse.sendRedirect( )?

Ans: The action allows the request to be forwarded to another resource

(servlet/jsp/HTMl> which are available in the same web-application (context).

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Where as in the case of Response.sendRedirect() the request to be

forwarded/redirected to another resource in the same web-application or some other

web-application in the same server, or to a resource on solme other web-server. The

key difference is by using single request from a browser can process

multiple resources. Where as by using SendRedirect( ) multiple requests take place in

order to process multiple resources.

13)Why beans are used in J2EE architecture instead of writing all the code in jsp's?

In order to seperate the business logic and presentation logic beans are used. We write

the business logic in the Beans. Where there is a change in business process we have to

modify only the bean code not jsp code and viceversa.

14)How can a servlet can call a JSP error page?

By simply includeing an tag in web.xml file

< error-page>

< exception-type>javax.servlet.ServletException

/errorjsp.jsp

By using Response.sendRedirect(error.jsp); or by using

RequestDispatches.forward(error.jsp); we can call jsp error page in servlet.

15)What exception is thrown when Servlet initalization fails?

ServletException . since init( ) throws ServeletException .

16) Explain MVC (Model-View-Controller) architecture?

MVC:- In model view controller design pattern, the software has split into 3 pieces.

MODEL-> Responsible for Managing Data-> Ex. Java Beans

VIEW-> Responsible for generating the views->Ex. Jsp's

CONTROLLER-> Responsible for user interactions & co-ordinate with MODEL

&VIEW

17)What are the design patterns? Explain FACADE Design Pattern ?

18) How do you perform testing? Do you use any automated testing tools? If so, whatare they?

19)Difference between Application Server & Web server ?Web servers are used for running web applications, the features are very less to

compare application server the application server is specific to application. And it

can run all the application including web application.

Ex:- weblogic,websphere, Jbose.

All are providing the more features than websever like tomcat.

Application servers used for enterprise solutions, webservers are used middle tier

webapplications. We can

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20)JSP implicit Object s:-

1)out: used to send the content to the browser

ex: out.println(xx)

2)Response: Represent HttpServlet Reques

3) Response: Represent HttpServletResponse

4) Page Context: used to access the objects like session, servlet context, Request,Response etc...

5) Session: Points to HttpSession objects

6) Application: Points to servlet context objects

7)Page: Points to current servlet objects

8) Exception: Points to Exception

21)JSP Action Tags, Directive Tags & Scripting Tags?

Action Tag: These tags effect the runtime behaviour of the jsp page and the

response

set back to client tags are :

instantiate a new jsp bean class

< jsp: setProperty>: setting the properties at runtime

:used to sending parameters

include a resource at runtime

forward the control to specific resource

:to plugin a web resource url applet

Directives:

These tags effect the overall structure of the servlet that result from translation. 3

types of directives are defiend.

Page directive: used to define and manipulate the no of page dependent

attributes that effect the whole jsp.

include directive: This instructs the container to include the content of the

resource in the current jsp

.

this file is parsed once, when translation.

Taglib directive: To use tag extendtions to define custom tags.

Scriptlets: There are used to include javacode in jsp page these are of 3 types

scriptlet: used to write pure java code

declarations: used to declare java variables and methods

Expressions:

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This send the value of a java expression back to client. These results is

converted to string and displayed at client.

22) tag and it's properties ?

To saparate the code from the presentation it would be good idea to encapsulate thecode in java object instantiate it and use it in our jsp. This instance is varaible is called

'id'.

We can also specific life time of this object by using 'scope' attribute

Properties:

id: a case sensitive name is used.

Scope: The scope with in which the reference is available. page, request,session,

application are possible values

page is default

class: the fully qulified classes name

beanname: The name of the java beanclass

type: This type must be super class of the beans classes

23)How do you implement Singe Thread Model in JSP ?

By simply include a page directives

24)How do you declare a page as Erro Page. What tag you include in a JSP page so

that it goes to specified error page in case of an exception?

By includeing a page directive

then this page is including a page directive in our jsp pages

calling this page is including a page directive in our jsp page

25)Difference between Include Directive & Incude Tag ?

26)Servlet is a java class. So, can there be a constructor in Servlet class or not? Why ?

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Include Directive Include Jas

before inclusion of resource

This include the resource at compilation

time

This is done at request processing time

It includes static content It include static or dynamic contentThis is parsed by container This is not parsed but included in place

27)What is a servlet Context? How do you get it ?

ServletContext is also called as applicatin object . And this can be used for

logging(stores some kind of information ) getting context parameters, getting the

request dispatcher and storing the global data.

We can get the serveletcontext using ServeletContext.

i.e ServletContext sc = getServletContext( );

28)What is Servlet Config? How do you get it ?

ServletConfig can be used to get the initiallization Parameters, to get the

reference to the ServeletContext. There can be multiple serveletconfig objects in a

webapplication.

Each servelet has one Config object.

The configration information is:

servlet name, initalization parameters servlet context object.

29)What is Request Dispatcher? How do you get it ?

The name itself reveals that it is used todispatch the control to requesting resource. It

is an interface used to include any resource with in our servlet or forward the

controoler to any other resource. It contains two methods.

Forward(---url);

forward(---url);

For getting this we have a method in servlet context interface. So we can get it by

servlet context object

sc.getRequestDispatcher( );

30)Tag Libraries, their syntax, & usage ?

31) Difference between JSP & Servlets?

Both are webapplications used to produce web content that mean dynamic web pages.

Bot are used to take the requests and service the clients. The main difference between

them is, In servlets both the presentation and business logic are place it together.

Where as in jsp both are saparated by defining by java beans .

In jsp's the overall code is modulated so the developer who deesn't know about java

can write jsp pages by simply knowing the additional tages and class names.

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One more important to be considered is servlet take less time to compile. Jsp is a tool

to simplify the process and make the process automate.

32)Difference between Hashtable & HashMap ?

Hash table is a Collection .To successfully store and retrieve objects from a

hashtable, the objects used as keys must implement the hashCode method and theequals method. Hashtable is Sychronized and permit not null values only.

Hashtable maps keys to values. Any non-null object can be used as a key or as a

value.

The HashMap class is roughly equivalent to Hashtable, except that it is

unsynchronized and permits nulls.

33) Question on Collections framework?The Collection API is set of classes and interfaces that support operations on

Collections of Objects.

34) By default, Hastable is unordered. Then, how can you retrieve Hastable elements

in the same order as they are put inside?

we can retrieve hashtable elements in the same order by using the method elements

which returns enumeration.

35) About Map data structures in Collections framework?

A map cannot contain duplicate keys; each key can map to at most one value. The

Map interface provides three collection views, which allow a map's contents to be

viewed as a set of keys, collection of values, or set of key-value mappings. The order

of a map is defined as the order in which the iterators on the map's collection views

return their elements.The TreeMap class, make specific guarantees as to their

order; others, like the HashMap class, do not.

36)Life Cycles of beans ?

37)Isolation levels & Transaction levels ?

The isolation level measures concurrent transaction's capacity to view data that have

been updated, but not yet committed, by another transaction if other transactions

were allowed to read data that are as yet uncommitted, those transactions could end

up with inconsistent data were the transaction to roll back, or end up waiting

unnecessarily were the transaction to commit successfully.

A higher isolation level means less concurrence and a greater likelihood of

performance bottleneck, but alos adecreased chance of reading inconsistent data. A

good rule of thumb is to use the highest isolation level that yields an acceptable

performace level. The following are commin issilation levels, arranged from lowest to

highest.

1) ReadUncommitted: Data that have been updated but not yet committed by a

transaction my be read by other transactions

2) Readcommitted: Only data that have been committed by a transaction can be

read by other transactions.

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3) Repeatable Read: Only data that have been commited by a trasaction can be

read by other transactions, and multiple reads will yield the same result as log as

the data have been committed.

4) Serializable: This highest possible iosolation level, ensures a transaction's

execlusive read-write access to data, it includes the conditions of ReadCommitted

and Repeatable Read and stiplulates that all transactions run serially to achievemaximum data integrity. This yields the slowest performance and least

concurrency. The term serializable in this context is absolutely unrelated to the

database.

38)ejbActivate( ) Vs ejbPassivate(), ejbCreate() Vs ejbPostCreate(), ejbLoad() Vss

ejbStore( ). Which type of EJB can use bean pooling? How can you call an EJB

from a JSP/servlet?

EjbCreate( ) is called before the state of the bean is written to the presistence storage.

After this method is completed, a new record is created and written to the presistence

storage. If you are developing an EJB following 2.0 specs, you can have overloading

methods in the form of ejbcreatexxx( ). This will improve the development so you can

have different behaviour for creating a bean, if the parameters differs. The only

requirement is that for each ejbCreatexxx( ) you need to have corrisponding

createxxx() methods in the home or local interface. EjbPostCreate( ) is called after the

bean has been written to the database and the bean data has been assigned to an EJB

object. So when the bean is available. In CMP, this method is normally used to

manage the beans container-managed relationship file

39)How to configure Data Source in WebSphere server ?

40)How you manage configuration control ?

41) What is a singleton class?

42)How do you send data from an applet to Servlet? What are the steps involved in it ?

When ever we send a request to the JSP file it checks the servlet representing the

JSP file. Then the web container runs the jsp compiler that generates the servlet

code

Directory

43)I have a file of very very large file size at client side, and i want to send the file to a

servlet(this servlet will store it somewhere), what is the best method to do it?

44)What is the difference between normal beans and EJBs ?

JavaBeans may be visible or nonvisibleat

runtime. For example, the visual GUI

component may be a button, list box,

graphic, or a chart

An EJB is a nonvisual, remote object

Java Beans are intended to be local to a EJBs are remotely executable components

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JavaBeans may be visible or nonvisibleat

runtime. For example, the visual GUI

component may be a button, list box,

graphic, or a chart

An EJB is a nonvisual, remote object

single process and are primarily intendedto run on the client side. Although one

can deevelop server-side JavaBeans, it is

far easier to develop them usin the EJB

specification instead.

or business objects that can be deployedonly on the server

JavaBeans is a component technology to

create generic java component that can

be composed together into applets and

applications

Even though EJB is a component

technology, it neither builds upon nor

extends the original javaBeans

specification.

Java Bean have an external interface

called the properties interface, which

allows a builder tool to interpret the

functionality of the bean

EJBs have a deployment descriptor that

describes its functionality to an exteternal

builder tool or IDE

45)How system level services in EJBs are managed? And tell about Deployment

Descriptor?

46)What are various types of EJBs ?

We have 3 types of EJB's

1) Seasion Beans:

Stateless Seasion bean

Stateful Seasion bean

Session beans are mainly used to implement business process applications

2) Enatity Beans:

Entity beans used to manage business entites

Bean Managed Persistance beans(BMP):--we need to write jdbc code to manage

business data

Container Managed Persistance bean(CMP):--Tools supllied as part of the

container generates the jdbc code for managing the data

3) Message Driven Beans: Used to implement business processing and Business

Data

47)What is the purpose of ejbLoad( )?

With CMP , the bean developer doesnot need to write any database access logic into

the bean, but bean is notified by the container when its state is synchronized with the

database. The container notifies the bean using the ejbLoad( ) and ejbStore( )

methods.

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The ejbLoad( ) method alerts the bean that its container-managed fields have just

been

populated with data from the database. This gives the bean an opportunity to do any

post processing before the data can be used by the business methods.

The ejbStore( ) method alerts the bean that its data is about to be written to the

database. This give the bean an opportunity to do any pre-processing to the fieldsbefore they are written to the database.

The BMP bean manges its own persistance , but relies on the container to

coordinate

its reads and writes so that persistance is accomplished in a transactional safe manner.

Coordination with the container is accomplished through two mechanisms:

the persistance callback methods [ejbLoad() and ejbStore()] and the Environment

Naming Context (EJB).

The ejbLoad( ) and ejbStore( ) methods notify a bean that its time to read and

write

data to the database respectively. In a BMP entity bean the code for reading and

writing data to the database is done with in these methods . The ejbLoad() is called at

the beginning of transaction, just before any business methods are executed , and the

ejbStore( ) is called at the end of a transaction just before its commited. This keeps

the bean state in perfect synchronization with transactions being executed , without

the bean developer having to explicitly manage the transactional operation.

48)What is the purpose of ejbStore( ) ?

49)What is the purpose of XML ?When ever we send a request to the JSP file it checks the servlet representing the JSP

file. Then the web container runs the jsp compiler that generates the servlet code

50) In webLogic clusters, what is the load balancing algorithm

Load Balancing for servlets & jsps

Load Balancing for EJB &RMI objects

Load Balancing for JMS

Load Balancing for JDBC connection

Round Robin Load Balancing

Weight based load Balancing

Random Load Balancing

Round Robin, weight based & Random affinity.

51)How many Queues does a MDB listen to ?

52)Where is the Deployment Descriptor placed ?

Deployment Descriptors gives the information about our resources used in our

application to the server. To avoid the hand coding we used these deployment

descriptors. Which are placed under WEB-INF directory as an .xml file

53)Can a JSP be converted to SERVLET and the vice versa always ?

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We can convert a JSP to servlet but it is not possible in case of servlet to a jsp.

Usually server takes the responsibility of converting a JSP to a servlet based on .tld

files and taghandlers. But there is no server which takes servlet as input and gives

jsp file as output.

54)About EJB types,CMP,BMP,session, Entity beans ?

Used for implementing business processing session beans are divided into two

types

1) Stateful Session Bean

2) Stateless Session Bean

In stateful Bean, state of the session is maintained. It takes more memory to

maintain the state for each object. If there are 100 clients/requests. The server

maintains 100 stateful beans each bean for a client. In stateless session Bean, no

need to maintain the state of a bean.

ii) Entity Beans: used to manage business data

BMP: we need to write jdbc code for managing data

CMP: code to manage the data will be generated by the tools.

iii) Message Driven Bean: Used for implementing business process ( some as

session beans use). This will be driven by message.

55)Can a client Context call ebjRemove( ) method ?

In ejbRemove( ) method will be called before removing the object, it is similar to

destroy( ) method in servlets. In case of stateless session bean we cant call

ejbRevove( ) method from client context. It depends upon the server when to

remove on delete the object from the server

In case of stateful session bean. The client can call ejbRemove( ) method by calling

remove method to remove the object from the server. In case of entity beans,

ejbRemove( ) method means deleting the data from two database. It can be called

from the client context.

56)Which is faster in execution-JSP or SERVLET ? Why ?

Servlet is faster in execution as every jsp is changed on converted to servlet before

starting the execution. Thus the server need to spend some time to convent a JSP

file to servlet at its first time execution. But developing a jsp is very easy when

compared to servlet.

Every time before executing a jsp & server searches for related servlet file. If it

existsWhen ever we send a request to the JSP file it checks the servlet representing

the JSP file. Then the web container runs the jsp compiler that generates the

servlet code

then start the execution of that servlet otherwise server creates servlet files for

those jsps first and then execution takes place

57) What is the difference between Callable Statement and Prepared Statement?

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Callable statement are used to call the stored procedures in a database where as

prepared statements are used to provide dynamic input for the statement.

58)Can we declare final method in abstract class ?

If a method is defined as final then we cant provide the reimplementation for thatfinal method in its derived classes i.e overriding is not possible for that method.

An abstract class constains one or mole abstract method. If all the methods ar of

type abstract then use we can declare that class as abstract or interface. But in

interface all the methods must be of type abstract.

We can declare final method in abstract class suspose of it is abstract too, then

there is no used to declare like that.

Final abstract int test(String str);

Here we cant provide the implementation for the test method as it is declared as

final. But at the same time you declare it as abstract. [Abstract means it is

responsibility of derived class to provide implementation for this] Here we cant

provide the implementation for the test method. Even we descried to provide

implementation totally our meaning for declaring it as abstract is spoiled.

59) Can we declare abstract method in final class?

It indicates an error to declare abstract method in final class. Because of final class

never allows any class to inherit it.

60)How can you pass an object of data from one JSP to anoter JSP ?

61) Can the same object os Stateless Session bean be shared by multiple clients?Can the same object os Stateful Session bean be shared by multiple clients?

It is possible to share the same object of stateless session bean by multiple

clients.

A Server maintains a pool of objects in case of stateless session bean. And

every When ever we send a request to the JSP file it checks the servlet

representing the JSP file. Then the web container runs the jsp compiler that

generates the servlet code

time for a request it uses one of the pool of objects which is free at that time.

The server gets back that object in to the pool only after the client work on

that object is Directoryover [ client says that by invoking ejbremove() method]

After the client release that object, the server may used the same object to

handle another client request, thus the same object to handle another client

request. Thus the same object of stateless session can be shared by multiple

clients But sharing the same object for multiple clients is not possible in case of

state full session bean. Here server should maintain an object for every clients

to handle / maintain the state of that object.

62)In java, which has more wider scope? Default or Private ?

Default has more scope than private

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Private: accessible only to the members of that class where it is defined.

Default: We can access this from any class in the program/file

63)Design Pattern ?

Design pattern is a solution for recurring (reoccurring ) problems. Any one

can provide best solution for a problem which is occurring repeatedly or oftenand we can give any name for that solution is known as design pattern.

64)Which Design Pattern hides the complexities of all sub-systems ?

65)Which bean can be called as Multi-Threaded bean?

Stateless session bean can be called as Multi-Threaded bean as for every

request of users is handled by creating a new threaded for the same object.

66) In CMP bean, which method executes only once in life time?

67)What is the difference between Server and Container ?

A server provides many services to the clients, A server may contain one or

more containers such as ejb containers, servlet/jsp containersetc. Here a

container holds a set of objects.

68)How will u authentication a user ?

69)Difference between SAX and DOM ?

SAX stands for Simple API for XML. It is a standard interface for

event based XML parsing. Programmers provide handlers to deal with

different events as the document is passed.

If we use SAX API to pass XML documents have full of control over

what happens when the event occur as result, customizing the parsing

process extensively. For example a programmer might decide to stop

an XML document as as soon as the parser encounters an error that

indicate that the document is invalid rather than waiting until the

document is parsed. Thus improve the performance.

DOM stands for Document Object Model. DOM reads an xmldocument into memory and represents as it as tree. Each node of tree

represents a particular piece of data from the original document. The

main drawback is that the entire xml document has to be read into

memory for DOM to create the tree which might decrease the

performance of an application as the xml document get larger.

70)Have u ever used how to include an xslt in another xslt ?

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The extensively Stylesheet Language (XSL) is a W3C standard for describing a

presentation rules that applied to xml documents. XSL includes both transformation

language an d formatting language. XSLT is an xml based language and W3C

specific that describes how to transform an xml document into another xml

document.

71)Which loads driver classloader or JVM ?

72)Types of Drivers in JDBC ?

Types of drivers in JDBC

Type 1 : JDBC ODBC Bridge Driver

Type 2 : Native API Partly Java Driver

Type 3 : JDBC Net pure Java Driver

Type 4 : Native Protocol Pure Java Driver

73)How to implement connection pooling by ourself ?

74) Will service all doget,dopost or the reverse?

75) How can u implement connection pooling by ourself?



code

76)How can u implement hasmap if u r not having it in java ?

77)How will u declare a synchronized block? What does this represent in the

Declaration of synchronized block?

When two or more threads need to access to a shared resource they need some

way to ensure that the resource will be used by only one thread at a time. The

process by which this achieved is called synchronization.

The general form of synchronize statement :

Synchronized (object) {

// statement to be synchronized

}

here the object is a reference to the object being synchronized. A

synchronized block ensures that a call to a method that is member of object

occurs only after the current thread has successfully entered the objects

moniter.

78) What is servlet chaining?

One servlet output will give as a intput of another servlet in servlet chaining.

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79)What is dynamic bindig? Can u explain with an example ?



code

80)Can u read all elements from any array ?

81)What is event delegtion model? Describe it with an example ?

The event Delegation model defines standard and consistant mechanisms to

generate and process events. A source generates and event and sends it to one or

more listeners. The listeners simply waits until it receives an event. The advantage

of this design is that the application logic that processes events is cleanly

separated from the uses interface logic that generates those events.

82)What is a tier? What is the difference between tier and system or computer?

83)What do u mean by portability ?

In c and c++ sizeof( ) operator tell us the number of bytes allocated for data

items. Different data types might be different sizes on different machines, so the

programmer must find out how big those types are when performaing operations

that are sensitive to the size. For example one computer might store integer in 32

bites, where as another might store integers as 16bits. So the java does not need a

sizeof () operator for this purpose because all the data types are the same size on

all machines. We need not think about protability.

84)What is translation unit in jsp ?

When we create a source code file for java its commonly called a compilation

unit or translation unit.

85) What is context in webapplication?

86)What are multiple and single processor servers? How session is handled when

the server is multi processor server?

When ever we send a request to the JSP file it checks the servlet representing theJSP file. Then the web container runs the jsp compiler that generates the servlet

code

87)If server crashes the threads will continue running or will they stop? What

happens to the servlet?

88)Explain MVC pattern by taking any one component ex JtextField or Jbutton ?

89) What is pooling of servlet?

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Whenever a request is called it picks up the instance of that servlet from a

Container which contains the number of instances from it & this is maintained by

the controls that is web.xml

90)Why cocoon? Why not struts? What is cocon ?

91)How is u implementing session in ur applicatin ?The web containers can create the session objects on behalf of client request. For

accessing this session objects we need to use request.getSession(Boolean value);

For every session object it is creating a sessionID to generate

92) What is serialization? What are the method in implementing serialization?


JSP file. ThDirectoryen the web container runs the jsp compiler that generates the

servlet code

93) Why jsp is used if we have servlets?

Java server pages are designed to simplify the process of developing a web

application on the top of servlet technology

94)Is servlet threadsafe ?

Yes Servlet is a thread safe by implementing the single thread model we can fulfill

this.

95) What happens when jsp is called?



code

96)When Jsp code changes, how the servlet is reloaded ?



code

97)What is difference between StateFul and Satateless Session Bean ?

98)What is difference between Bean ManagedPersistance and Container

ManagedPersistance?

IN the case of Bean Managed Persistant we need to write the manual coding

but in the case of container managed persistant bean the tool itself will

generate the code to satisfy our requirements

99) Difference between forware(request,response) and SendRedirect(url)inservlet?

In the case of forward (req, res) the outputs generated by the first servlet will be

discarded but only the output generated by the second servlet will be send to the

client . But in the case of send redirect() will be setting the status code & pointing to

the new url.

100)Draw & explain MVC Architectur ?

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101) What is synchronizing?

With respect to multithreading , synchronization is the capability to control the access

of multipul threads to shared resources . Without synchronization, it is possible for

one thread to modify a shared

object while another thread is in the process of using or updating that object's value.This often leads to significant errors.

102)How to prevent Dead Lock ?

We can prevent this Dead Lock by implementing synchronization proceder &

improve the efficiency of the Application.

103)How Servlet Maintain Session and EJB Maintaine Session ?

104)Difference between HasMap and Hash Table ?

In the case of Has Maps there is no synchronizable in the case of Has Table it is

synchronizable and thread safe but it is slow in performance.

105)Difference between Swing and AWT ? AWT is heavey weight , where as Swings are light weight. These two are

using to implement GUI applicatins.

106) Types of Enterprise Bean?1)Session Beans.

2)Entity Beans

3)Bean managed persistant Bean.

4)Containes Managed persistant Bean

5)Message Driven Bean.

The above 5 are the Enterprise Entity Beans.

107)Service of EJB ?The EJB provides the following services

a)concurrency

b)Transaction Management

c)Persistancy

d)Security

e)Threading

f)Synchronization

g)Object cashing

h)Object Naming

i)Object activation

j)Object serialization

k)Object sharing

l)Object communication

m)Object Decision

108)Why not to use free J2EE servers ?

109)Alternative:Tuxedo ?

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110)J2EE server offeres ?

It offers servlets, JSP,JNDI,JDBC & structs.

111)J ava Naming and the Directory Service?

It is Noting but Java Native Device Interfaces where we can store our remote objectinside the file & this is used to identify the Home object

112) XML deployment descriptor?

It is nothing but web.xml where we can store all the resource information of all the

objects inside this file

113) Entity Bean session Bean where to use which Bean? Container Types:

114) What is the Max amount of information that can be saved in a Session Object?

As such there is no limit on the amount of information that can be saved in a

Session Object. Only the RAM available on the server machine is thelimitation. The only limit is the Session ID length(Identifier) , which should

not exceed more than 4K. If the data to be store is very huge, then it's

preferred to save it to a temporary file onto hard disk, rather than saving it insession. Internally if the amount of data being saved in Session exceeds the

predefined limit, most of the servers write it to a temporary cache on Hard

disk.

115) How to confirm that user's browser accepted the Cookie?

There's no direct API to directly verify that user's browser accepted the

cookie. But the quick alternative would be, after sending the required datatothe users browser, redirect the response to a different Servlet which would

try to read back the cookie. If this Servlet is able to read back the cookie, then

it was successfully saved, else user had disabled the option to accept cookies.

116) How do i get the name of the currently executing script?

Use req.getRequestURI() or req.getServletPath(). The former returns thepath to the script including any extra path information following the name of

the servlet; the latter strips the extra path info. For example:

URLhttp://www.javasoft.com/servlets/HelloServlet/jdata/userinfo?pagetype=s3&pagenum=4

getRequestURI servlets/HelloServlet/jdata/userinfogetServletPath servlets/HelloServlet/getPathInfo /jdata/userinfogetQueryString pagetype=s3&pagenum=4

117) What are Good Ways of Debugging a Servlet? Are IDE's which support Servlet

Debugging?

There are couple of Methods. Firstly servers like JRun and others provide separate

logs where all your Print requests will print their data into. For example requests to

System.out. and System.err go to different log files. If this features is not available or

you want to maintain logs separately for each module then you can create a static

class called "LogWriter" and call the method inside the try catch loop. The print

method in Log Writer will be writing to a custom defined Log File.

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try

{ ....}

catch(Exception exp){

LogWriter.print("Debug : The following error occurred at function .... ')

}Also Inprise JBuilder supports Servlet Debugging. Please refer to JBuilderdocumentation for details.

Just as a Cautionary note, from your Servlets, never call System.exit(0). Theresults might be unpredictable. Might close down the entire Server. The Best

way is to catch the Exception and either send resultant Error Page to theBrowser or Write to a Log file and inform user about the Error.

118) How do I know when user Session has expired or removed?

119) How can i stress test my Servlets?

You can use one of the following products to stress test your Servlets.

ServletKiller From Allaire Software (Free Product)

E-Load from RSW Software

Web Application Stress Tool From Microsoft

JMeter from Apache

120) What is Server Side Push and how is it implemented and when is it useful?

Server Side push is useful when data needs to change regularly on the clients

application or browser , without intervention from client. Standard examples

might include apps like Stock's Tracker, Current News etc. As such servercannot connect to client's application automatically. The mechanism used is,when client first connects to Server, (Either through login etc..), then Server

keeps the TCP/IP connection open.

It's not always possible or feasible to keep the connection to Server open. So

another method used is, to use the standard HTTP protocols ways ofrefreshing the page, which is normally supported by all browsers.

This will refresh the page in the browser automatically and loads the new data

every 5 seconds.

121) What is the difference between Multiple Instances of Browser and Multiple

Windows? How does this affect Sessions?

From the current Browser window, if we open a new Window, then it referredto as Multiple Windows. Sessions properties are maintained across all these

windows, even though they are operating in multiple windows.Instead, if we open a new Browser, by either double clicking on the Browser

Shortcut icon or shortcut link, then we are creating a new Instance of theBrowser. This is referred to as Multiple Instances of Browser. Here each

Browser window is considered as different client. So Sessions are not

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maintained across these windows.

123)Difference b/w jsp:forward and request.sendRedirect.

124)Using which obj we can call trasnsaction control statements.

125) Question on native with synchronized is it possible?

126) Can more than one will have his state in stateful session bean?

127) How u can database operations used in stateful session bean?

128) What do we use as path in xml?

129) What is struts?

130) Explain MVC Architecture?

View : - The UI view involves the presentation layout(the actual HTML

output), for the result of the interaction . For HTML clients, this can be done usingJSP.

Controller : - presentation logic (the logical connection between the user and

EJB services), necessary to process the HTTP request , control the bussiness logic,

and select an appropriate response . This can be provided by Java Servlets or Session

Beans.

Business logic (Model) :- The business logic ( the core business transactions and

processing ), necessary to accomplish the goal of the interaction ( calculations, queries

, and / or updates to a database ,etc). Business logic should be separated from

UI logic. This makes it possible to have different clients( for ex browser and GUI)

using the same beans . Separating the 2 also makes the business components easier to

re-use , maintain, and update or change.

131) How you can create servlet objects at the time of web application starts?

1

a) if we use configure a servelet using Load-on-startup the webContainer creates our

servlet object when we deploy the webapplication.

b) when we undeploy the webapplication the webcontainer destroys ( removing the

object from JVM destroys the servelet object ).

132) Suppose i created 5 servlet objects dynamically and i make a request to the

container, the which object will give to me?

133)What is the difference between servlet config and servlet context?

There will be only one ServletContext object for a webapplication.

There can be multiple ServletConfig objects in a single webapplication.

Servlet Config can used get Parameters

134) How you can create a connnection object in weblogic? And how you can access

that object?

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135) What is difference between jsp:forward and Reqdisp.forward( )?

136) What is difference between Req.sendRedirect and reqdisp.forward( )?

137) How you can insert values into a table without writing the code( )?

138) How you can call a jsp from a servlet and vice versa?

139) What is the difference between jsp writer, printwriter?

140) What are the implicite variables in jsp?

141) How may ways you can use threadclass and in which situation you can be use

runnableinterface?

142) What is the difference between string and String Buffer?

143) What is the difference between SAX and DOM?

144) If we can implement a constructor in a servlet? What will be happen?

145) What is difference between stateless and stateful session beans?

Stateless:

1) Stateless session bean maintains across method and transction

2) The EJB server transparently reuses instances of the Bean to service different

clients at the per-method level (access to the session bean is serialized and is 1 client

per session bean per method.

3) Used mainly to provide a pool of beans to handle frequent but brief reuests. The

EJB server transparently reuses instances of the bean to service different clients.

4) Do not retain client information from one method invocation to the next. So

many requir the client tomaintain on the client side which can mean more complex

client code.

5) Client passes needed information as parameters to the business methods.6)

Performance can be improved due to fewer connections across the network.

Stateful:

1) A stateful session bean holds the client session's state.

2) A stateful session bean is an extesion of the client that creates it.

3) Its fields contain a conversational state on behalf of the session object's client.

This state describes the conversation represented by a specific client/session object

pair.

4) Its lifetime is controlled by the client.

5) Cannot be shared between clients.

146) What are the disadvantatges of CMP?

147) Structs concept you are implementing on model1 or model2?

148)What in an interface?

149)What are the difference between interface and abstract class?

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The key difference between an interface and the corresponding abstract class is that a

class or interface can have unlimited number of immediate super interface but it can

only hace one super class.

There are two primary axes of inheritance an object-oriented language like java.

Implementation inheritance is where the sub-class inherits the actual code

implementation from the parent. Interface inhyeritance is where the sub-class adheresto the public interface of the parent.

Also java actally mixes the two notions together a bi.... java interfaces are nice and

clean. When you implement an interface, you are stipulating that your class adheres to

the contract of the interface that you spefified. Java class inheritance isn't so clean

when you sub-class in java you are getting both the code inheritance but you are also

stipulating that you sub-class adheres to the contract of the interface of the parent

class.

Abstrct class in java are just like regular java classes but with the added constraint

that you cannot instance then directly. In terms of that added constraint, they are

basically classes which don't actually implement all lof the code specified by their

contract.

150) How you can access the implementation from the database to JSP/Servlet?

151) How you can get connection object from weblogic?

A checked exception is an exception that must be dealt with in the code, either by

catching it or by specifying a throws clause. Checked exceptions are all exceptions that

are subclassed from Exception except RuntimeException. An unchecked exception is

an exception that need not be dealt with programmatically. It includes

RuntimeExceptions (and its subclasses) and Error and its subclasses.

================================================================

==== Checked vs. unchecked exceptions There are two kinds of exceptions in Java,

checked and unchecked, and only checked exceptions need appear in throws clauses.

The general rule is: Any checked exceptions that may be thrown in a method must

either be caught or declared in the method's throws clause. Checked exceptions are so

called because both the Java compiler and the Java virtual machine check to make

sure this rule is obeyed. Whether or not an exception is "checked" is determined by its

position in the hierarchy of throwable classes. Figure 4 shows that some parts of the

Throwable family tree contain checked exceptions while other parts contain

unchecked exceptions. To create a new checked exception, you simply extend another

checked exception. All throwables that are subclasses of Exception, but not subclasses

of RuntimeException are checked exceptions.

152) How you can send parameters to a servlet?

153) How you can create global parameters that is the parameters which are used by

all the servlets?

154) How many types of transactions are supported by EJB? What are they tx-

support,tx-no.supported what is the difference between tx-required,tx-not supported?

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REQUIRED : Method calls require a transaction context. If one exists , it will be

used ; if none exists, one will be created.

Can use Existing Transaction.

If not already in transaction will start new one , commit when method completes.This

transaction attribute should be used when ever the bean is accessing any transactional

resouce manager. ForEx: a bean accessing a database through JDBC should use thetransaction attribute Required. You should use this if you want the operation to

always run in a transaction.

TX- NOT-SUPPORTED :

The bean runs out side the context of a transaction. Existing

transactions are

suspended for the duration of method calls.

Does not execute in a Transaction.

Existing transaction is suspended.

This transaction attribute can be used when the resource manager

responsible for transaction

is not integrated with the application server. ForEx, if the bean method is invoking an

operation on a SAP System which is not integrated with the application server, the

server has no control over the transactions happening at the SAP system. In such a

case , it is best to set transaction attribute of the bean to be Not-Supported.

155) Explain about checked and unchecked exceptions?

A checked exception is an exception that must be dealt with in the code, either by

catching it or by specifying a throws clause. Checked exceptions are all exceptions that

are subclassed from Exception except RuntimeException. An unchecked exception is

an exception that need not be dealt with programmatically. It includes

RuntimeExceptions (and its subclasses) and Error and its subclasses.

================================================================

==== Checked vs. unchecked exceptions There are two kinds of exceptions in Java,

checked and unchecked, and only checked exceptions need appear in throws clauses.

The general rule is: Any checked exceptions that may be thrown in a method must

either be caught or declared in the method's throws clause. Checked exceptions are so

called because both the Java compiler and the Java virtual machine check to make

sure this rule is obeyed. Whether or not an exception is "checked" is determined by its

position in the hierarchy of throwable classes. Figure 4 shows that some parts of the

Throwable family tree contain checked exceptions while other parts contain

unchecked exceptions. To create a new checked exception, you simply extend another

checked exception. All throwables that are subclasses of Exception, but not subclasses

of RuntimeException are checked exceptions.

156) How you can create dynamically servlet objects at the time of webapplication

deploying?

157) What is the difference between function and procedure in oracle?

158) What is the difference between drop and truncate?

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159) What is the difference between truncate and delete?

160) Suppose you are doing any actions on database but you system will not doing any

actions on database? How you can know about this thing?( By starting logging

information in a file)

161) Servlet are by defaulty single threaded or multiple threaded?

162) What is the syntax of jsp:usebean?

jspusebean syntax:

163) What is the difference between reqdis.forward(),jsp:forward?

jsp:forward is a Action tag in jsp which is used to forward the request from one

page to other page . This is similar to requestDespatcher.forward.

In requestdespatcher forward ,only one request will be sent by the browser

and it is processed by two servlets/jsps.

164)What is a view?

View in a Mvc pattern is containing the presentation logic.

We are using jsps as view in MVC architecture.

165) What is the difference between callable statements, prepare statements ,

createstatements?

callable statements: callable statements are used to retrieve the stored procedures

from the database. ie., these statements are used when two or more sql statements are

retrived over and over.

prepare statement: theser are precompiled statements which are stored in

database. We are using these prepare statemnts if the same query is to be executed

over and over.

statement: statement is used to execute single sql statement.

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