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Collections
What is the difference b/w 2d array and hashmap?Where we have to use this?Explain ? Thanks in advance
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How will you make session more secure in JSP?
elanchezhian
- Jun 11th, 2012
By using Cookies
mani.sivapuram
- Feb 14th, 2011
since sessions are created by server only but by using session with cookies (or) session with url encoding techniques we set the session id in the client system.If we want to maintain secure data abou...
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How would you go about designing a better system?
Interviewer asked me this question in a interview. I could not give a clear answer. Can someone please help me to answer this question? Or point me to the websites that talk about How to Design a Good Software System. Thank you very much.
mani.sivapuram
- Feb 14th, 2011
when we want to solve a particular problem we are going to face so many problems and at last we are going find how to tackle this type of problem in future then if many people are using that par...
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Interface and Abstract Class Usage
When will you use an interface and abstract class?
mani.sivapuram
- Mar 8th, 2011
the simple way we can answer is in interface we can provide only abstract methods(i.e the methods with out any implementation) and in abstract class we have abstract methods as well as concreate metho...
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What is the purpose of singleton design pattern?
mani.sivapuram
- Feb 10th, 2011
Singleton design pattern is used to create only one instance.I want to a an example when we are using this singleton design pattern in real life.generally the dao classes like insertDao,updateDao,dele...
shreesha.s
- Sep 5th, 2010
Singleton Design Pattern is used when we would like to have a single instance. A class distributes the only instance of itself. It will be used with Connection Pool usually.
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Use of Static
What is the use of static in (public static void main string args[])
amrutabhavana
- Sep 4th, 2011
We can use static key word for any method which does not require an object to call, so main method is automatically called by the JVM so it does not require any object it is mentioned as static. We ca...
Suresh
- Aug 6th, 2011
Without creating instance of that class to invoke the main method static keyword is used, by giving the name of the class main method gets invoked.
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Object Class
When you declare a class, why does it automatically extends to object class? Give 2 reasons.
mani.sivapuram
- Mar 11th, 2011
When preparing the Java by JavaPeople they thought like every object what we prepare should have some common property so that we can do some basic operations like for example clone() method. So ...
anandkumarjha
- Aug 9th, 2010
Object class is the super class of all the classes provided by java.lang package. And I think you know that all the basic functions to write a program like println() are the content of the class...
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Object Class Methods
Why wait() and notify() are used only for threads, why not to objects?
kalaiselvigurusamy
- Jun 11th, 2010
The wait() and notify() methods are object-specific. The wait() method suspends the current thread of execution, and tells the object to keep track of the suspended thread. The notify() method tells t...
jeetu1607
- May 30th, 2010
wait(), notify() and notifyAll() are in Object class because the lock for these are set on a object and these can be called on any object. Any threads accessing the object will be put into wait status...
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Primitive Types
What happens when you add a primitive type (e.g. double) value to a collection?
pdureja
- Apr 6th, 2011
Collection can hold Objects but not primitives. Prior to Java5, we need to wrap primitive using wrapper classes and in java 5 autoboxing do it automatically.Prior to java 5:xyzCollection.add(new Integer(10))In javaxyzCollection.add(10) //will do autoboxing
mani.sivapuram
- Mar 11th, 2011
Every one says that every concept in Java is purely prepared in Object Oriented Form only in you need to remember one thing when Java people preparing the Java they try to create an alter native t...
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Find the Output
class A{ public static void main(String[] a){ System.out.print(String.valueOf(1)+String.valueOf(2)); String s1="s1"; String s2=s1.toString(); System.out.print(","+(s1==s2)); }}
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Double Value
What happens when you add a double value to a String?
mani.sivapuram
- Mar 14th, 2011
Here consider String s="java"; Double d=new Double(1.4); Here when we write s="java" an object of type String is created and it is referenced to 's'.In the similar way when we write Doub...
Sarje
- Aug 20th, 2009
When you add Double value to a String first the double value will be converted to String and appended to original String and new compelet String object will be created.For exam:String str = "Ram";Double d = new Double(12.50d);str = str + d;now str is "Ram12.50"
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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 Heirarchy of Files
What is heirarchy of files in Struts?
mani.sivapuram
- Feb 15th, 2011
When we send the request from client then first it touches the ActionServlet--->RequestProcessor---->ActionForm(do the required validations)---->Action (execute method is executed)---->Service class(i...
ameesala
- May 14th, 2009
When the request is recived by ActionServlet it looks for the ActionMapping entries in the Struts-config.xml. ActionMapping returns the appropriate Action class where we handle the business logic.Finally execute() returns the ActionForward key (View).
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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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difference between Struts 1.x and Struts 2.x
What is the difference between Struts 1.x and Struts 2.x
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Dependency injection
What is dependency injection ?
lwpro2
- Mar 8th, 2011
Spring terms of Inversion of Control is called dependency injection.Instead of creating dependency class B instances from Object A (A--> B), dependency injection is the design pattern suggesting the r...
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java patterns
Explain java patterns in detail? Any difference between Design patterns and java patterns ? . Explain about advantages of using patterns with an example.
mani.sivapuram
- Feb 28th, 2011
In java total 23 design patterns are there those 23 is subdivided into three types as given below1. Creational design patterns2. Structural design patterns3. Behavioural design patterns1.Creational de...
manivannan57
- Nov 21st, 2008
It can't be explained in one or two lines. You gotta read nearly 23 patterns in OO. And, write yourself some application. You have to have application knowledge of patterns than theoritical knowledge. I'll recommend you to go through the book written by GangOfFour
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What is the DAO design pattern
mani.sivapuram
- Mar 7th, 2011
Generally in the previous projects they write the code for controller's and code for interacting with database like inserting, updating, deleting etc...will be done at one place. But if you see th...
Shail2009
- Jan 12th, 2010
Use DAO design pattern to abstract and encapsulate all access to the datasources. The DAO manages connection with the datasource to obtain and maintain data.
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What is the actual purpose of using framework in realtime applications?
mani.sivapuram
- Feb 15th, 2011
To reduce the developer effort we will go for the framework. Because in the old projects are implemented with some pattern and they find some sort of common problems so all the common problems are sol...
g lingareddy
- Jul 3rd, 2010
Frame work automatically generate ActionServlet which is reduce the work of programmer. In traditional Servlet/JSP project programmer explicitly write Actionservlet
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What is the advantage of using static methods in real time applications?
When we use static methods and when we use final methods? Explain with a suitable example..
mani.sivapuram
- Feb 10th, 2011
Generally static methods are loaded when we load the class into JVM itself.so without creating any object we can access those methods.
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What J2EE design problems does Hibernate solves apart from Data Base in-dependency and being an ORM tool?
mani.sivapuram
- Feb 14th, 2011
Since in case of jdbc autocommit is always true but in case of hibernate after executing all the sql statements only it process the commit operation this is called as transaction management.But this t...
prashant82
- Jun 24th, 2009
In hibernate objects are loosely coupled providing flexibility during integration with other databases or applicationsIn J2EE inheritance can not be achieved directly for the objects mapping One-to-one mapping is mandatory in J2EE
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Which (stack or heap) memory will be allocated when an object is created using new operater?
mani.sivapuram
- Feb 10th, 2011
When an object is created using new operator then JVM creates object and place that object in heap memory. and stack area is used to store object referances and methods and variables.
mmptce
- Sep 25th, 2007
Heap memory is allocated for the objects and the instance variables that are created by using new operator.Stack memory is for the method call and thread call.
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Explain saveToken() function
mani.sivapuram
- Feb 17th, 2011
When we send the request once to the server then we should disable that button otherwise the user may thought that the request is not sent so he send the request again and again. Here the problem is w...
DEBABRAT
- Nov 24th, 2007
saveToken() method is used for duplicate form submission.Let's take an example i.e. yahoo email registration formYou filled the form and press the "submit" button more than once.For each action you do...
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What are the Action Classes?
mani.sivapuram
- Feb 10th, 2011
Action classes are like controllers in MVC architectures.Since when we send the request to server then action class is going to do the operation like it take the data from request object and send it to service layer according to required operation.
mabhijit
- Jan 11th, 2008
The action classes are the link between the Struts framework and your business application logic. The fact that the main method in the action class is called "perform" indicates that the act...
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What is the difference between and merge and update
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Editorial / Best Answer
promisingram- Member Since Oct-2008 | Oct 19th, 2008
Use update() if you are sure that the session does not contain an already persistent instance with the same identifier, and merge() if you want to merge your modifications at any time without consideration of the state of the session. In other words, update() is usually the first method you would call in a fresh session, ensuring that reattachment of your detached instances is the first operation that is executed.
Thomas John
- Sep 21st, 2015
I create an object say Employee with id 1. I create this object by getting the student record from the database. Object s1 is in the session Employee e1 = null; Object o = session1.get(Employee.cl...
Mukesh Vishwakarma
- Aug 25th, 2015
Update will work at same session. After close the session or detached the state, update will not work.
But in the case of Merge after closed the session it will work. -
What is Hibernate proxy?
arindam_0006in
- May 19th, 2008
Proxies are created dynamically by subclassing your object at runtime. The subclass has all the methods of the parent, and when any of the methods are accessed, the proxy loads up the real object from...
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Where do we use the Bridge Design Patterns?
mani.sivapuram
- Mar 7th, 2011
Bridge design pattern is used where to decouple an abstraction from implemention so that they can vary independently.
raj9753
- Jan 13th, 2010
IN JDBC we use this pattern as the implementations of all the interfaces is totally dependent on the different DB Vendors.
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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 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 the difference between hibernate and Spring
mani.sivapuram
- Feb 21st, 2011
Hibernate is used to interact with database.i.e if we want to save some data then we use hibernate or jdbc or some other tools available in the market.But it is not possible for struts or spring to st...
srini
- May 3rd, 2007
Hibernate is ORM tool used for data persistency.Spring is a framework for enterprise applications with default APIs for presentation, middle tiers and presistence layers and allows to integrate with ...
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Is Action class is Servlet or Not ? if yes why ?
mani.sivapuram
- May 5th, 2014
Action class is not a servlet but it is having the properties like a servlet. For example servlets have request and response objects similarly action classes is also having request and response object...
PS
- May 17th, 2013
No.. Action class is not a servlet. The only servlet class in plain struts framework (without spring etc.) is ActionServlet.
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What is database persistence?How well it is implemented in Hibernate
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Editorial / Best Answer
mani.sivapuram- Member Since May-2010 | Feb 14th, 2011
There are mainly three states in hibernate
a) Transient state
b) Persistant state
c) Detatched stateTake the employee object place the data in that object like usename, password, empid. Now the state of the object is transient state, when we write the statement given below
session.save(employeeObject);
Now the state of the object is persistent since the employee object is kept in session object then when we write the statement given below
transaction.commit();
When we apply the above statement then the employee object is going to linked with database and the data is stored in related table of that database. Since the emp object in persistent state only the data is stored in database other wise the data is not stored in database.
After the commit operation it becomes into detached state. If anybody wants to store the emp object into database then in detached state it is not possible.
mani.sivapuram
- Feb 14th, 2011
There are mainly three states in hibernate a) Transient state b) Persistant state c) Detatched state Take the employee object place the data in that object like usename, password, empid. Now th...
prasadkuppa
- Apr 24th, 2008
Preserving the data inside a database is database persistence. Persistence is once of the fundamental concepts of application developement. There are many alternatives to implement persistence. Object...
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what is switch action & forwardAction in struts
mani.sivapuram
- Feb 15th, 2011
when we are using multiple modules in that case i need to maintain different struts configuration files so i need to provide multiple struts configuration files in the web.xml in such situation i use ...
ArulMurugan
- Feb 13th, 2007
A Forward Action is a standard Action forwards the request to the context-relative URI(JSP/Servlet) specified by the parameter property of the associated ActionMapping.To configure the use of the For...
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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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I am using hibernate.What is the use In Data(POJO) class primary key is sending as an argument with constructor?
mani.sivapuram
- Feb 14th, 2011
since according to the hibernate specifications hbm file is configured in such a way that one primary key shoud be configured in id tag of hbm file.and other properties are configured in property tags...
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why servlet is used as controller ?not JSP? i want complete Explation?
In struts servlet control the application and we know that a jsp compiled into a servlet first. The only problem with the servlet is that it needs to write out.println call per HTML line. But as a controller in struts servlets do not force the programmers to write out.println, that is the part of JSP which acts as View.So if the controller would be JSP the translation (JSP compiled to a servlet)step...
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Why do you need ORM tools like hibernate?
mani.sivapuram
- Feb 14th, 2011
since we want to reduce burden on the developer so for big projects if any maintaince is requered then problem finding and bug fixing is easy in case of hibernate.I can obey with one thing it we need ...
meetaskjain
- Mar 8th, 2010
Hibernate allows the application developer to concentrate on the business logic instead of writing complex SQLs. Aprt from this hibernate would take care of the database connections and managing conne...
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What is component mapping in hibernate?
Thomas John
- Sep 21st, 2015
Hibernate component represents as a group of values or properties, not entity (table). I have a customer table that has address fields. I will create 2 models - customer, address. In this case, Addres...
mani.sivapuram
- Feb 21st, 2011
I will explain one realtime scenario here.Consider one Address class as given belowpublic class Address{private Integer doorNo;private String street;//provide setters and getters for above properties}...
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what is lazy fetching in hibernate
mani.sivapuram
- Feb 14th, 2011
Lazy fetching means for example in hibernate if we use load() method then load() is lazy fetching i.e it is not going to touch the database until we write empobject.getString("eno");So when we write a...
Karuna Reddy
- Aug 22nd, 2008
Lazy loading is the responsibility is that to load the objects for its parentIn mapping file, if
you want to load the child objects while loading the parent it will wont load coz by default load = trueso
you have to specify lazy = falsehere child class become parent while loading the objects. -
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what is diff. between MVC1 and MVC2?
mani.sivapuram
- Feb 17th, 2011
MVC1:-----In case of MVC1 Jsp is used as both view and controller.And JavaBean is used as Model i.e to persist the data into database Controller--->JSP View --->JSP ...
Srinivas
- Sep 4th, 2006
MVC is generlised architecture. There is no MVC1 and MVC2. According to Sun Microsystems in MVC Model1 driven architecture Controller and view is JSP and model is bean. In MVC model2 driven architecture we will use Servlet as controller, JSP as view and Bean as Model.
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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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How Data Access Object (DAO) class will handle the data
Suppose there are 2500 records to be handled? How Data Access Object (DAO) class will handle it?
mani.sivapuram
- Feb 14th, 2011
When we send the data from front end like JSP or HTML etc then the controller is going to take the data and send it to service layer the service layer takes that data and send it to DAO layer in DAO l...
phdsong
- Aug 26th, 2008
DAO is one of design patterns. The Data Access Object (or DAO) pattern: 1. Separates a data resource's client interface from its data access mechanisms, 2. adapts a specific data res...
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what is difference between object and Premitive data
Parag jain
- Jul 5th, 2016
Data objects are collection of one or more piece of data and data type is only one type of data like int, char, float
Sukhrob
- Dec 24th, 2015
Primitive data types like byte, short, int, double, long they store data while object only has reference to the declared data. When object type called it references to the declared type.
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What is the difference between Abstract Factory Pattern and factory Pattern?
What is the difference between Abstract Factory Pattern and factory Pattern? When would you use each of them?
mani.sivapuram
- Feb 23rd, 2011
Abstract factory pattern is same as like factory pattern but in abstract factory pattern we prepare a base class as abstract and we provide the implementation classes to the base class. In the clie...
rkj2ee2005
- Mar 19th, 2006
Abstract factory pattern is typically used for giving implementation to specification (eg., jdbc, servlet specifications etc...). Factory pattern is used when you want to defer object creation to lat...
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what is difference between runnable and thread ?why we use static class
AMIT GURJAR
- Sep 21st, 2012
Sir please tell me that when a thread never return desired result then why we use it?
prabakaran29
- Aug 19th, 2012
Thread class can be extend only one class where as we using runnable interface can be implement many classes.so runnable interface is the best to implement the block of code
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What is the right way of writing the code to get the servlet information using public String getServletInfo()?
mani.sivapuram
- Feb 23rd, 2011
By using the page directive as given below<%@ page info="hi this is the way
to write the code for getServletInfo() method" %>
mabhijit
- Jan 11th, 2008
Some applets and applications, for example, the Java Web Server Administration Tool, display information about a servlet. This information can include a short description of the purpose of the servlet...
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What is connection pooling?
CareerBaba.in
- May 7th, 2014
Opening database connection is a time consuming operation. Connection pooling increases the performance of the applications by reusing the active database connections instead of create new connection ...
mani.sivapuram
- Feb 23rd, 2011
In the previous days database connections are maintained by database only for example oracle database is having 10 database connections are there.Consider at the same time 10 clients are asked for a p...
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What is the difference between String and StringBuffer? Which is better to use in project?
mani.sivapuram
- Apr 14th, 2011
String is a immutable.What is immutable the state of an object is not changed if we initilize once.i.e for example String s1="Geek" ...
sankarsansinha
- Feb 5th, 2009
String objects are constants and immutable where as StringBuffer objects are not.StringBuffer Class supports growable and modifiable string where as String class supports constant strings. Strings onc...
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what is diffrence between java and java script?
amreenkhader
- Jan 20th, 2012
Java is the basic object oriented programmng language and Java script can be used in style sheets making and in HTML documentation
mani.sivapuram
- Feb 23rd, 2011
java-script is also same as like java only.But java is used in server side scripting and the javascript is used in client side scripting. I will say a real time scenario here consider the normal user...
