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Sub Class of Action Class
class A extends ActionSupport{ }class B extends A{}Is B also acts as an action class or not? Explain
vinaymudgil007
- Feb 3rd, 2011
Yes, it will be an action class and in my opinion I would say its an action class even if it doesn't override any method. This goes with the rule of inheritence.Thanks,Vinay
vkankane
- Sep 5th, 2010
Yes if all the methods of the action class defined in Class B then it is sure act as a Action class.
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ODBC & JDBC
What is the purpose of creating ODBC data source in establishing a connection between Java application & database?
sindhumsc
- Aug 24th, 2010
ODBC stands for open database connectivity which helps us to connect then link from Java to database..so if we want to connect from Java to any database one way is to use ODBC which helps to connect Java to any database (like Oracle, MySQL..).
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JDBC-ODBC Bridge
When would you use a JDBC-ODBC Bridge?
vinaymudgil007
- Jun 7th, 2010
We use JDBC-ODBC bridge only when pure JDBC drivers are not available [say for connecting to a database] otherwise pure Java drivers are a good optoion.The use of JDBC-ODBC drivers isn't recommended v...
hsavinash2001
- May 26th, 2010
It is not recommended to use because of the dependency on native language (This is implemented in C++)
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JDBC Isolation Level
Name the method that gives the existing isolation level in JDBC.
vinaymudgil007
- Jun 7th, 2010
Just to add more info to the above answer (public int getTransactionIsolation() throws SQLException from Connection interface) that their is always a trade-off between isolation level and concurrency ...
awasie
- Nov 14th, 2009
Isolation level represent how a database maintains data integrity against the problems like dirty reads, phantom reads and non-repeatable reads which can occur due to concurrent transactions. java.sql...
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Session and Cookie
What is the different between session and cookies? Where is the session information stored? In RAM of the Client or Disk of the Client or it is stored on the server?
vinaymudgil007
- Aug 30th, 2009
well, the purpose of session and cookie is the same --- to maintain the state [in a typical web application, based on http protocol]Session -- Its stored at server side [containers memory, R...
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Struts Framework
Why we use Struts framework in project?
mani.sivapuram
- Feb 15th, 2011
Generally in any project we should use any design pattern to make project success. So many people find some sort of problems in their design but atlast they provide one solution to those common probl...
vinaymudgil007
- Feb 3rd, 2011
Benifits of using struts framework are [these are the reasons we should use struts]:-(1) Its based on MVC architecture [MVC-2 to be specific] and brings a clear line of demarkation between Controller ...
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Struts ActionServlet
why do we have only one ActionServlet in Struts?(Asked in Polaris Interview for Java Experienced people , on April 11, Chennai)
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wasNull() method to handle null database fields
which of the following methods eliminates the need to call wasNull() method to handle null database fields?a)getObject()b)getInt()c)getString()d)getFloat()e)getNull()
vinaymudgil007
- Jun 8th, 2010
To my understanding, the question isn't framed properly. The answers given by two fellows above are ways to go around this situation but none eliminates the need to call wasNull().Other views are appreciated !!!
kittupeddi
- Apr 10th, 2008
Two Ways:1> Use the wasNull() method on the ResultSet.2> Use the getObject() method on the ResultSet and do the Comparision.
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A user leaves an online shopping cart without checking out.Which of the following interfaces will notify to rollback the transaction?
A user leaves an online shopping cart without checking out.Which of the following interfaces will notify to rollback the transaction?a)HttpSessionb)HttpSessionBindingListenerc)HttpServletd)SingleThreadModele)FtpSession
vinaymudgil007
- Jun 8th, 2010
(b)HttpSessionBindingListener is the correct answervalueBound() and valueUnbound() are the methods that should be over-ridden to get this implemented.Thanks.Vinay
phanikhk
- Apr 9th, 2008
Any class can implement HttpSessionBindingListener interface. This interface includes two methods, valueBound() and valueUnbound(), that are called whenever the object that implements the interfa...
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Servlets are multi threaded by default. If there are concurrent requests to the same servlet the servlet container generates another instance of the servlet . Is this the reason y servelts are multi threaded by default?? Is there any way the multi threaded feature can be achieved ?
vinaymudgil007
- May 21st, 2008
one thing surely i can say and that is "only one insatnce of the servelet would be created" and multiple threads would be used to serve the request.......well if the requests are very large ...
AjayMukiri
- Apr 30th, 2008
Servlets are multi threaded by default. If there are concurrent requests to the same servlet the servlet container generates New Thread . So this the reason servelts are multi threaded by default.
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What will happen if the mapping to actionform in the struts-config.xml is mentioned wrong?
vinaymudgil007
- Feb 7th, 2011
Its pretty trivial that their will be a http status 500 error stating that the requested resource wasn't found.The reason is:--Its the job of the ActionServlet to create the actionform instance fo...
rammaheswara
- Dec 22nd, 2008
Nothing will happen at that instant. In the action, if we try to cast the action form and using it, then it will throw nullpointer exception.Regards,Mahes.
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What is the use of Service() in servlets? How is that method invoked?
vinaymudgil007
- Aug 30th, 2009
Service method is used to serve to client [which intern calls doGet/doPost methods depending on type of requests].......This service() method is called by the servlet container....Thanks,Vinay
myogeshchavan97
- Jul 26th, 2009
When init() method returns successfully then only service() method is called by the servlet container.This method handles each new request coming from the client and new thread is created in the same ...
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What are the Database transactions? How we can maintain transactions using JDBC? Explain with example?
vinaymudgil007
- Jun 8th, 2010
Database transactions => A group of SQL queries which should either all be executed or none should be executed will comprise of a tracnsaction.Maintain transactions using JDBC => We can do ...
trcdutt
- Feb 15th, 2008
Here is a skeleton of code for implementing a transaction.import java.sql.Connection;public class Test {public void AllTransactionStatements() { Connection con = getCon(); &nbs...
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What's going on
Is the driver get registred then where it is inintialized, if it is initialized & registerde there only, How?">In the Statement below class.forName(" ---");What's going onIs the driver get registred then where it is inintialized, if it is initialized & registerde there only, How?
vinaymudgil007
- Jun 8th, 2010
class.forName(" Any Class Name Here") is a static method in Class class which returns the Class object associated with the class or interface with the given string name.....So when I say cl...
subhankar1982
- Feb 21st, 2009
Every JDBC driver vendor providing a static block for Driver classprovided by vendor. Which taking care of creating driver class object and registaring driver class , so instead of writing code Ex:- D...
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How will you determine which driver is connected to the database
can u give correct answer for this....!
vinaymudgil007
- Jun 8th, 2010
public static Enumeration getDrivers() method in java.sql.DriverManager class will do this for us.Some more useful information below:public class DriverManager is the basic service for managing a set ...
Nitesh Gupta
- Sep 10th, 2007
Through MethodDriverManger.getDriver(url) you will get the driver name.
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Why object class is parent for every class?
Ajay
- Sep 12th, 2018
The main reason is Inheritance. If you observe the methods in Object class, contains the basic methods that every class should contain and they are very basic features or functionalities that every class should have and support.
Also there are many reasons for that...jawaharl0207
- Oct 22nd, 2009
Because it has methods like useful for all the classes, like wait, notify, notifyall, clone and gc, these methods are common use for all classes.
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ResultSet is an interface, How does it support rs.next()?
NAVEEN
- Jun 18th, 2007
Question: If Result Set is an interface, then why can we call methods like next(), isLast() etc. without defining the method body anywhere in the program? As I understand it, in an interface, methods...
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How many ActionServlets are created by struts based application?
mani.sivapuram
- Feb 15th, 2011
When the client sends the request for that request one thread is created for that particular client. In te same way if multiple clients are send the request for the same web page here multiple threads are created with regarding their own ActionServlets so no confusion in between the clients.
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What is the use of writing empty catch block?
vinaymudgil007
- Jul 31st, 2008
Just catch the exception & swallow it [don't take any action].that's all.vinay
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What is the difference between dynamic method dispatch and method over riding?
vinaymudgil007
- Jun 9th, 2008
Sampra -- what you said is correct but don't you think that over-ridding itself uses dynamic method dispatch....what i am trying to say is that the line demarcation is very thin.vinny
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What are advantages and usage of static block?
pdommara
- May 28th, 2010
The above answers are missing important point that is it even runs before your class constructor.
vinaymudgil007
- Jun 10th, 2008
static block is executed whenever a class is loaded by the JVM.....hence in case you want certain code to executed or say some objects of a class avaliable to ur application as soon as the application starts you can put in the relevant code there....vinny
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What is the return type of DAO in Struts?
mani.sivapuram
- Feb 15th, 2011
There is no specification for the struts in DAO so DAO can send back any object to the action class.
vinaymudgil007
- Feb 7th, 2011
Struts doesn't lay a guideline for DAO layer for a programmers so I would say that the return type in a DAO is up to the programmers discretion.Thanks,Vinay
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What is data object?
vinaymudgil007
- Jun 10th, 2008
Boss..... the question isn't clear!! im not sure if we have some trminology as "data object".please elaborate
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What is the difference between store procedures and prepared statement?
vinaymudgil007
- Jun 8th, 2010
To be straightforward, we can only compare two things when they are in the same scope/domain. This question says to differentiate b/w SPs and prepared statements isn't valid.Stored Procs are persi...
subhankar1982
- Feb 21st, 2009
Generally procedure and functions are written in PL/SQL code and it will reside in databases. When we develop some application in Java using JDBC to deal with specific databases for specific purpose...
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What is the state of Connection object after execution of Statement(Populated Result Set)?
vinaymudgil007
- Jun 8th, 2010
The connection object is still open after the excecution unless explicitly closed by Connection.close() method.
venu
- Apr 10th, 2007
The connection object is still active, meaning it is ready to execute another statement.
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What is the use of BLOB, CLOB datatypes in JDBC
vinaymudgil007
- Jun 8th, 2010
These are used to store large amount of data into database like images, movie etc which are extremly large in size.Thanks,Vinay
madhuhari
- Apr 16th, 2007
BLOB(Binary Large Object) and CLOB(CharacterLargeObject) are SQL2 datatypes, which are introduced in JDBC 2.0 version. Suppose you have a requirement like, you want to store your content of resume(la...
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HiRecently at an interview I was asked the following question:Create a hashtable A, assign key value pairs to it and then set A to null. Will it be garbage collected?Please reply.
jimmy514in
- Oct 31st, 2010
Objects which have null references are garbage collected ..But you can just request the garbage collector algo to start..you cannot command it..so when it would be collected is not known..Also, a null reference attached to object is called as weak referenceAnd weak references are garbage collected.
vinaymudgil007
- Jun 11th, 2008
Yes the hashtable would be avaliable for garbage collection BUT when actually is would be collected that would depend on JVM garbage collection cycle.vinny
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What is difference between Html tags and Struts specific HTML Tags
MuthuKumaran
- Jul 15th, 2014
HTML tags are static and Struts tags are dynamic. Struts tags can be created by the page authors. Binding of the property value with the Formbean property is done by the Struts tags. HTML tags support...
mani.sivapuram
- Feb 15th, 2011
Struts html tags internally uses normal html tags only but the differnce is to reduce the developers task internally we implement normal html and those are abstracted and we provide in terms of struts specific html tags.
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How to call a static block in one class from another class?. And is it possible to call a free floating block in one class from another class?. How?
vinaymudgil007
- Jun 11th, 2008
static block gets executed whenever is class is loaded by the JVMso what you can do is.....write is class having static block in it ---> compile it --> write another class (ensure that fir...
NavaNani
- Apr 7th, 2008
Non static blocks & Static blocks are executed one by one by the order of their defintion before any constructor is being executed.Static blocks can also be invoked without creating instance ...
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can i have more than one ActionServlet class file in my application?
sriragv
- Nov 28th, 2009
We can have more than one Action Servlet but Struts controller follows the front controller design pattern. As per this pattern we will have only one controller. Designing more than one action servlet is breaking the rule of design pattern.
coolsiva
- Sep 22nd, 2009
Yes, but stuts-config definition are stored in the application scope with a key so when the second definitions comes in the web.xml, the second struts-config overrides the previous one.
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Should every html form property have a corresponding formbean get/set and variable.?Can form property be omitted in a form bean?
rammaheswara
- Jul 23rd, 2009
No.It is not neede to have every html form property have a corresponding form bean get/set and a variable. For Ex. "submit" button is form property which may not be required to ca...
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Static methods are override or overload ?
vinaymudgil007
- Jun 12th, 2008
Guys to my knowledge..... we can overload but can't override static methodsvinny
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can i write marker interfaces,if yes how can i?
vinaymudgil007
- Jun 12th, 2008
Yes you can write marker interface.A marker interface is the one which doesn't have any methods declared in it e.g. Serializable etc.Here you go as marker interface...............interface thisIsAMarkerInterface{ }vinny
shashidhar reddy
- Dec 1st, 2006
Hi Sunil, can u briefly explain this.Is it possible to write userdefined marked interfaces &...
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in which class public static void main(String ar[]) is declard in java
sat.beit
- Jun 6th, 2008
Main method define in class from which excution of the application will get start.Which u can called main class of the file and file name will be the same as mainclass.
dvs198528
- Jun 6th, 2008
Public static void main(String ar[]) is in the class whose name is same as the name of the program name.Reason : To start the execution of the program initiating from main().
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Hi, can we declare non static variables in static methods?if so plz explain by an example?
vinaymudgil007
- Jun 12th, 2008
yes, we can declare and they would be local to the block.Here is an example.....class Test { public static void main(String[] args) { ...
Seema
- Feb 2nd, 2007
Declaration of i is outside static method, so it is giving error "can not make static reference to non static field" if it is declared inside then it will print 10.
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Why class Class is always the Super Class for every class
ashish
- May 20th, 2012
1. Object is super class for all java classes.
2. even if someone want to make a class as subclass of CLASS class, he cant because class class is declared as final. so it can not be inheritedvinaymudgil007
- Jun 12th, 2008
Java.lang.Object is the super class of all classes and NOT Class classvinny
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name two classes that can store arbitrary number of objects
vinaymudgil007
- Jun 12th, 2008
This is one of the resons we have Collections framework in javaexamplesArrayList , Vector , Set -- directly as objectsHashTable, HashMap -- as objects as ket-value pairsvinny
Amit Rastogi
- Oct 5th, 2006
Any collection which is not having singleton or unmodifieable modifier can store any no of objects
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//this.disp();
}
void t3()
{
System.out.println("Enter to t3 void");
}
}
On what situation void type constructors are used?">class t3{ int i; static public void main( String a[]) { int j=8; t3 t= new t3(); new t3().disp(j); } //constructor overloading t3() { System.out.println("Enter to t3"); //this.disp(); } void t3() { System.out.println("Enter to t3 void"); }}On what situation void type constructors are used?
vinaymudgil007
- Jun 12th, 2008
Constructor's don't have any return-type....... and hence when you precede void with constructor java comipler treats it as a METHOD of that class and not as constructor!!!vinny
chinnu
- Nov 18th, 2006
Actually constructor means one type of special methods in java. It returns nothing even void also. These are used for intilising the objects with same parameters and different parameters.
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what is the difference between abstract class & Final class
Manjunath_7_89
- Mar 25th, 2016
Abstract Class
1. Could be Inherited.
2. Couldnt instatiated.
3. Could add few more methods.
4. Incomplete class
Final Class
1. Final version of Class
2. Couldnt be inherited.
3. Could be instantiated.
4. Couldnt add any more methods.baban
- Feb 11th, 2016
Abstract class cannot create object but final class create a object
abstract class which have must a subclassed but final class which have no subclassed -
Can we override the main method?
Read Best Answer
Editorial / Best Answer
ashish_setia- Member Since Oct-2006 | Oct 3rd, 2006
check out this example
class Checkmain{
public static void main(String args[]){
args[1]="ashish";
System.out.println("hello ");
}
}
class Checkmain1 extends Checkmain{
public static void main(String args[]){
System.out.println("how r u");
}}
class Jo{
public static void main(String args[]){
String S[]=new String[10] ;Checkmain.main(S);
Checkmain1.main(S);
}}vivek
- Aug 26th, 2017
Yes you can only do that by overriding main method signature for eg main(String[] args) to main(). Certainly there are no other ways to do that because JVM needs strings array arguments to take comma...
Dharmendra Singh
- Sep 15th, 2016
yes we can"java public class HelloWorld { // arguments are passed using the text field below this editor public static void main(String[] args) { String []s =new Str...
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if i give two Class.forName how can i konw which driver is loading? whether it is possible or not?
vinaymudgil007
- Jun 8th, 2010
Yes it possible.... Please see public static Enumeration getDrivers() method in java.sql.DriverManager.DriverManager class which gives the complete list of Drivers available for use as an Enumeration.Thanks,Vinay
Supriya Ahire
- Feb 2nd, 2007
Hello, Yes , U can use two Class.forName() as Drivermanager keeps array internally to store the Drivernames so whichever come first will we loaded & used.Regards, Ms.Supriya Ahire
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how can container will know this is a struts application?
mani.sivapuram
- Feb 17th, 2011
Here one thing i want to finalize i.e everything is working on servlet container only i.e we need only serlet container not sturts container .since when we deploy the application into the servlet cont...
vinaymudgil007
- Feb 7th, 2011
The control is forwarded from the container to struts controller when is reads an entry like :-- <servlet-name>action</servlet-name> <serv...
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If interface has got four methods,and I like to implement only two methods, how this could be achieved?
Karuna Reddy
- Jun 5th, 2008
Rest of the two method to open it and close the braces.EX:interface in1{ public void A(); &nb...
Karuna Reddy
- Jun 1st, 2008
public interface MyInterface1 { public void A(); public void B();public void C();public void D(); }package com.venkata.ust; public class MyClass1 implements MyInterface1 { @Override pu...
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what r the disadvantages of struts?
vinaymudgil007
- Feb 7th, 2011
Personally I have used struts for quiet a long time and the limitations mentioned on the link uin the above post, I haven't encountered any of them, So my experience says that its a very nice framework to work upon.Thanks,Vinay
Vijay
- Aug 14th, 2006
Few Disadvantage are mentioned in the below link. Struts have disadvantages mainly on performance of the application. Especially when using advanced tag like nested-loop etc, Resulting in creating man...
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what is garbage collection? can it be forced?
Karuna Reddy
- Jun 6th, 2008
Garbage Collection: If no longer any obejct need to any variable, java automatically reclaimes the memory.U can't force the GC, U have to give the request by using system.gc() and even not guarante that its immediatly to reclaims the memory...........
vinaymudgil007
- Jun 5th, 2008
garbage collection means releasing the memory free from the objects that can no longer be refferenced.No it can't be forced.............. although system.gc() or whatever may request for garbage collection but when exactly it would be started is at the discretion of JVM.
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What is the difference between Inheritance and Aggrigation?
vinaymudgil007
- Mar 21st, 2011
Inheritence means --> "is-a" relationshipe.g. HONDA CITY is-a CARAggregation means --> "has-a" relationshipHONDA CITY has-a engineHope this makes it clear !!!
navneetgoyal2000
- Jan 5th, 2011
If we have to explain it with example, then Inheritance (IS A or TYPE OF) & Aggregation (HAS A) can be understood as:a CAR IS A (an) Automobile. (Inheritance: Car inherits its properties from Automobile)Whilea CAR HAS A (an) engine. (Aggregation: Car Class has an Object of engine class)
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How can we work struts on Eclipse? What is the best plugin for this?
vinaymudgil007
- Feb 7th, 2011
As mentioned above by someone in these posts that "excadel" is one populer plug-in for using it with eclipse.And well if you are not rigid with using it with Eclipse only, I would suggest you to use it with NetBeans [say 6.9.1] and I am sure you would like it.Thanks,Vinay
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I want to know output of this program and the flow alsopublic class Aquestion { private int i = giveMeJ(); private int j = 10; private int giveMeJ() { return j; } public static void main(String args[]) { System.out.println((new Aquestion()).i); } }
talktoatish
- Aug 16th, 2009
public class Foo { private static int j = 10; private static int i = giveMeJ(); private static int giveMeJ() { System.out.println("in the method" + i + j); return j; } public static void...
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What is serialization?What is transient?What is the default value of a transient variable?
vinaymudgil007
- Jun 10th, 2008
serialization -- means saving the state of an object at a particalar instance of time.transient -- appended before a variable to ensure that the valiable is not saved during serailizationdefault value -- well, that has nothing to do with serailization, it depends on the data type of the variable
Ganesh Bala Kumar
- Aug 14th, 2006
Hi,State is nothing but the present values of the class level variables and behaviour (methods) of the class.Suppose if u r having setters and getters in ur class , when u retrieve the values into the...
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in struts why we use jsp as presentation layer? can we use servlet as presentation layer?
vinaymudgil007
- Feb 7th, 2011
Well if you don't want to follow MVC [mvc-2], struts [or anyone] doesn't stop you from doing that.If you don't do it, then you will loose the benifits that come along with the mvc architecture.Thanks,Vinay
U.Vellaisamy
- May 21st, 2006
jsp1.Struts framework is basically using the taglib so we can import taglib, it is possible for jsp elements.Directive tag<%@ taglib uri="WEB-INF/struts-bean.tld" prefix="bean.tld"%><%@ ...
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In struts, if any changes are made to before the request reaches to actionservlet, where you do the changes?
vinaymudgil007
- Feb 7th, 2011
I think what you are looking for from this query is that you want some of your custom [application speicifc code to be in place before you processes a request], then it can be achieved in following tw...
Shipra Dey
- Nov 18th, 2006
I suppose ... We can do it by making a new class which will extend the RequestProcessor or TilesRequestProcessor whicever is mentioned in config file tag and give the path.I hope this will do
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in struts why we use servlet as action controller?
vinaymudgil007
- Feb 7th, 2011
We do this in order to reap benefits of MVC [mvc-2] pattern.And BTW, this question isn't specific to struts I believe.Thanks,Vinay
Ajit
- Apr 4th, 2007
Since the very purpose of having a controller in the struts framework is to redirect the request to the appropriate action class to process the correspnding business logic, and servlet is th...
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what is the protocol is used in type4 driver?
vinaymudgil007
- Jun 8th, 2010
Per my understanding and knowledge over the years, its the Native [java specific] protocol that is used in type4 drivers !!!Thanks,Vinay
Spoorthi
- Sep 13th, 2006
jdbc:oracle:thin:@localhost:1521: our GlobalDatabasename
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in overriding, in super class we declared a method as protected & in sub class we declared that method as private. what happens?
vinaymudgil007
- Jun 4th, 2008
Well the answer to orignal question asked is -- compilation errorlogic --> In a subclass we can't make the method more restrictive than what is there in the super class.vinny
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3.which one is better to create a thread by implementing Runnable or By Extending Thread in java?">
1.why constructor does not have return type in java?2.why static does not support " this" and "super" keyword in java ?3.which one is better to create a thread by implementing Runnable or By Extending Thread in java?
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type="com.test.LoginForm"/>
path="/login"
type="com.test.user.login.LoginAction"
name="loginForm"
validate="false">
Question: Assuming the class LoginForm contains a String property named "password", how does the LoginAction class access the attribute called "password" in the above request? Explain why.
Choice 1
String password = request.getParameter("password");
Choice 2
String password = request.getAttribute("password");
Choice 3
request.getParameterNames().getParameter("password");
Choice 4
String password = ((LoginForm) form).getPassword();
Choice 5
String password = form.getPassword();
">Question: Assuming the class LoginForm contains a String property named "password", how does the LoginAction class access the attribute called "password" in the above request? Explain why.Choice 1 String password = request.getParameter("password"); Choice 2 String password = request.getAttribute("password"); Choice 3 request.getParameterNames().getParameter("password"); Choice 4 String password = ((LoginForm) form).getPassword(); Choice 5 String password = form.getPassword();
vinaymudgil007
- Feb 7th, 2011
Choice 4
String password = ((LoginForm) form).getPassword();
is the appropriate answer wrt struts framework.
Thanks,
Vinay
prasad.juturi
- Aug 24th, 2009
If the values are set from a JSP, then we need to follow the request.getAttribute() method and while revalidating the fileds, the request.getParameter() method?will be fired.The reason for the above t...
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what is the diff between perform() and execute() method?
vinaymudgil007
- Feb 7th, 2011
The new method execte() is necessary because perform() method declares that it throws only IOException and ServletException. Due to the added declarative exception-handling functionality the framework...
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Is there any way to define a default method for every in the action mapping of Struts-Config.XML file? If yes then how? Give a piece of code demonstrating the same.
vinaymudgil007
- Feb 7th, 2011
Overriding org.apache.struts.action.RequestProcessor is another solution I would suggest.Thanks,Vinay
krishnachaitanya.v
- Jul 8th, 2008
use unknown = true tag in action tag of struts-config.xml.With this, the action mapping will be defaulted if no matching path is found.Eg:<action-mappings><action path="/example&quo...
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1)what happens if i do this=null?2)how to swap 2 variables without using third temp variable in java?3)constructors can not be inherited,why?
vinaymudgil007
- Jun 10th, 2008
The answer given above by Mr. Satish------------------------------------------------------------------------------------------a= ((a+b)-(a-b))/2b= ((a+b)+(a-b))/2--------------------------------------...
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When many Users are browsing the same application at the same time and they click the "Submit" button will many objects be created for each and every User?
umar farooq
- Jul 24th, 2011
NO, There will be one single instance of the servlet in the web-container ,when request arrives to the server a thread will be created rather creating the object. so that multiple request will have ...
vinaymudgil007
- Mar 31st, 2011
Single servlet object will be loaded in memory and one thread per request would be created by the container to serve those requests.Thanks,Vinay
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how and when to prevent inheritance?
vinaymudgil007
- May 29th, 2008
Two ways: -(1) mark the class as final(2) make its constructor private -- in this case we will also not be able to instantiate a class from any other classany doubts, let me knowVinny
iyck
- Jul 5th, 2006
If we make Final class we cannot extend, also if we make all the constructor private then we cannot extend that class, is this also prevents inheritence?
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difference between local and global transaction?
vinaymudgil007
- Jun 8th, 2010
The primary difference is that local transaction are single JVM level while global transaction are at multiple JVM level and hence global transactions need different design approach [which can be clas...
ak40732
- Mar 21st, 2006
A transaction is atomic unit of Work.The tasks which are made into the transaction act as a unit which can be executed successfully all,or if at least one task fails to its promise ,then the effect of...
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what is the difference between servlet context and servlet config
vinaymudgil007
- Feb 7th, 2011
Servlet Config 1 Servlet config are one per servlet per JVM 2 It's inside the servlet it won’t accessible to outside the servlet. Ex: <servlet>            <init-p...
Rohit
- Jul 22nd, 2007
Servlet Config parameters are set for the servlet initialization, these information is necessary for the servlet startup, eg.: Database connectivity, other xml files. etc.Servlet Context are used by t...
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in Execption handling What is exactly difference between throws and throw?
Karuna Reddy
- Jun 1st, 2008
Throw: We can use our own exceptions ie User Defined Exceptions.Throws: we can raise the exceptions more than one at a time
vinaymudgil007
- May 29th, 2008
Throw -- used to throw an exception explicitlyThorws -- indiacates the calling method that the called method my throw specified exceptionVinny
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State true or falseCan we retrieve a whole row of data at once, instead of calling an individual ResultSet.getXXX method for each column ?
A) TrueB) FalseExplanation: The ResultSet.getXXX methods are the only way to retrieve data from a ResultSet object, which means that you have to make a method call for each column of a row. It is unlikely that this is the cause of a performance problem, however, because it is difficult to see how a column could be fetched without at least the cost of a function call in any scenario.
vinaymudgil007
- Jun 8th, 2010
We can update the Row with the values of the result set via updateRow() but we can't fetch it and hence the answer is "NO" or falseThanks,Vinay
Praveen
- May 17th, 2006
we cannot retrieve a whole row of data at once.In JDBC getXXX() are the methods which are used to get the data from ResultSet by columnwise.
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Which of the following statements is true regarding the failing of the class.forName in jdk 1.1.x.
A) A workaround is to explicitly call the method DriverManager.registerDriver(new YourDriverClass).B) The problem is due to race condition in the class loader.C) The race condition prevents the static section of code in the driver class from executing and registering the driver with the DriverManager.D) All the above.
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Which of the following is true regarding not finding the java.sql.DriverManager class.
A) This problem can be caused by running a JDBC applet in a browser that supports the JDK 1.0.2, such as Netscape Navigator 3.0. The JDK 1.0.2 does not contain the JDBC API, so the DriverManager class typically isn't found by the Java virtual machine runningB) Most of the browsers cannot download java.* because of security reasons. Hence many vendors of all-Java JDBC drivers supply versions of the...
ajay
- Nov 21st, 2014
A
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What’s the difference between TYPE_SCROLL_INSENSITIVE , and TYPE_SCROLL_SENSITIVE?
A) A result set that is TYPE_SCROLL_INSENSITIVE does not reflect changes made while it is still open and one that is TYPE_SCROLL_SENSITIVE does.B) Both types of result sets will make changes visible if they are closed and then reopened.C) You will get a scrollable ResultSet object if you specify one of these ResultSet constants.D) A result set that is TYPE_SCROLL_INSENSITIVE makes the result set read...
vk payne
- Feb 8th, 2013
A,B and D
All the three are correct
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Which of the following statement is false regarding the use of setAutoCommit() in JDBC
A) When a connection is created, it is in auto-commit mode.B) If the value is true each individual SQL statement is treated as a transaction and will be automatically committed right after it is executed.C) once auto-commit mode is disabled, no SQL statements will be committed until you call the method commit explicitlyD) By default the JDBC call is in auto-commit mode.Explanation: by default the JDBC...
Harish
- Apr 10th, 2018
Answer is : D
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what are the other ways to prevent a class from being subclassed.one way is to declare the class final.does declaring a class private prevent it from being subclassed?
vinaymudgil007
- May 21st, 2008
Pankaj Vishwani.....your code is compiling because you have prefixed the kerword void before the constructor of stud class...... hence its not a constructor anymore.... its beheaving like a method as ...
Ram
- Jan 8th, 2007
Well pankaj. The deal is to make the constructor private. In your example you have created a method as private as constructor do not have any return type. So try compiling again. cheers. Ram
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I need some more information about interface. For Example there is no any functionality inside the method which is declared in any interface. Then why i want to implement that interface to my class. 2. Statement is an interface. When i say stmt.executeQuery(). I am getting the records in my ResultSet. How it is possible?.. since there is no functionality insid the methods which is declared in Statement Interface. What is happning here?
An idea
vinaymudgil007
- Jun 3rd, 2008
Well the answer given by sarat is a very good one & explains the concept.....
sasi
- Jul 20th, 2006
hi.....for example..take SUN as example..they provides..only interfaces..that means..they give only NULL implementations..i.e.what is the returntype of the interface..what is the method & it...
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Can we use any other technology than JSP to construct a view ?
Yes, other than JSP we can use Swing, JSF, Cocoon etc as a front end for our struts application. Here is a link to the article for using struts with swing as front end
vinaymudgil007
- Feb 7th, 2011
I think that flex is quiet popular these days apart of JSF, swings, velocity which can be used.Thanks,Vinay
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I want to create two instances of a class ,But when trying for creating third instance it should not allow me to create . what i have to do for making this?
vinaymudgil007
- Jun 3rd, 2008
Here is a code snippet that will create maximum of two objects.*******************************************************************//This is a class that will create maximum of two objects for itself.c...
naveen.jayaram
- Sep 30th, 2005
by keepineg count of number of objectsfor examplepublic class ThreeObject{ private ThreeObject() { // no code req'd } public static ThreeObject getThreeObject() { int count;...
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Whether a Class,Method can be garbage collected or not?How?
MMK143
- Mar 28th, 2010
Class and Method are not garbage collected because class and methods are the predefined instruction formats for developing an object oriented programming.
umesh_kilkile
- Mar 23rd, 2010
No. Class and methods aren't garbage collected.Because Class is a logical construct in that we write methods or logics.When we run Java program, class gets loaded in main memory that is RAM and method...
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Is there any way to put my custom name to LIB folder which i am going to place in WEB-INF folder of struts application?
please answer this question
vinaymudgil007
- Feb 7th, 2011
I don't know if its possible [if anyone knows please share how its possible].But may I know why this is required?
geeksterrahul
- Aug 3rd, 2009
The possibility is "YES" when you can change the Server configuration.But no one wants to change the server configuration(will cause more problems).So the answer is: Although it's possible it's not recommended that you change the server configuration.
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Can we declare multiple main() methods in multiple classes.ie can we have each main method in its class in our program?
r.praveenkumar
- Aug 6th, 2008
Yes I tested this we can have main method in two different classes this will not give error and we should save that doc with the class name which has the main we want to be executed first and inside t...
vinaymudgil007
- Jun 3rd, 2008
Yes this is possible...... but within a single file only one class can be declared puiblic!!!!and whichever class you run, that class's main() mentod would be called.......vinny
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do we have a constructor in servlet ? can we explictly provide a constructor in servlet programme as in java program ?
bharathwatch
- Jul 9th, 2011
Servlet container creates object for our class when the default constructor is there in our class..if not provide then container will take care about that...
ankita surendra bimal
- Feb 12th, 2011
No, we dont have a constructor in servlet as the objects in servlet are created by webserver.
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When you have an object passed to a method and when the object is reassigned to a different one, then is the original reference lost
Aqan12
- Jun 4th, 2010
Primitives are always passed by value.Objects: Passed by value of reference. i.e. a copy of reference is passed into the method. Any changes to the reference itself will not be visible outside the met...
Scorpio_
- May 7th, 2010
Mr Ashutosh Gupta,Java is pass-by-value. For primitives, you pass a copy of the actual value. For references to objects, you pass a copy of the reference. You never pass the object. All objects are stored on the heap. Always http://www.javaranch.com/campfire/StoryPassBy.jsp
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Do primitive types have a class representation
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Explain the keywords - native, transient, volatile, finally
vinaymudgil007
- Jun 2nd, 2008
Native :- Specifies that the code that should be implemented is writtern in a language other than JAVATransient :- Specifies that the associated variable should NOT be serializedVolatile :- directs th...
Siva Prasad Ashwini
- Oct 17th, 2005
native:when you want to get functionality from particular language like c/c++ native is usedTransient : it is state of which value doesnt persist volatile : is an indication to the compiler that ...
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What is the difference between ServletContext and ServletConfig?
Both are interfaces. The servlet engine implements the ServletConfig interface in order to pass configuration information to a servlet. The server passes an object that implements the ServletConfig interface to the servlet's init() method.The ServletContext interface provides information to servlets regarding the environment in which they are running. It also provides standard way for servlets to write...
lavanyarani
- Nov 9th, 2009
ServletContext and ServletConfig are the interfaces provided by java class in servlet API.The vendors of web containers(WC) provides the classes implementing these interfaces.It is the responsiblity o...
jawaharl0207
- Oct 22nd, 2009
ServletConfig gives the information about the servlet initialization, it is an interface, where as ServletContext holds the information about whole application(project), the servlet container will create the object of ServletContext. Each servlet has its own ServletConfig object.
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What is the difference between GenericServlet and HttpServlet?
GenericServlet is for servlets that might not use HTTP, like for instance FTP service.As of only Http is implemented completely in HttpServlet. The GenericServlet has a service() method that gets called when a client request is made. This means that it gets called by both incoming requests and the HTTP requests are given to the servlet as they are.
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What are the three statements in JDBC & differences between them
Answered by Jey on 2005-05-10 05:53:50: 1.Statement which is used to run simple sql statements like select and update 2. PrepareStatment is used to run Pre compiled sql. 3. CallableStatement is used to execute the stored procedures.
Naveen Sharma
- Jul 31st, 2011
Class.forname is used to load a class.
When we are making database connectivity then class.forname(................) must be the first statement.Harish Chevuri
- Jun 3rd, 2011
three statements in jdbc1. statement : whic is used to execute select and non select queries.2. PreapreStatement : which is also used to execute select and non select queries but PrepareStatement whic...
