J2EE Interview Questions

Synchronization is the process of allowing threads to execute one after another. Synchronization control the access the multiple threads to a shared resources. Without synchronization of threads, one ...

Creating thread is basically instantiate the Thread class. There are two ways to instantiate class: with extend or implementation of interface.

The main difference of creation of hashmp instance

HashMap hm = new HashMap(); Here we are getting the HashMap methods only will get inherited.

Where as
Map mp= new HashMap(); // Here will get the Map interface methods inherited into class.

Class can be protected or private but only inner

The class cannot be declared as protected..

Can override init & destroy .
People used to make mistakes by overriding inti(ServletConfig).
Because if we override and forget to call super.inti(ServletConfig) then default actions doesnt get performed. As a result getServletConfig() will return null.

It is possible to Override init() & destroy() methods in servelts

Project Architecture is nothing but is structure of your application. What are the layers are used to retrive the data from the Database."java Presentation Layer ----------->Contr...

The architectures is nothing but how many layers will be there and which technologies are involved on each layer. 1) View Layer -------------> JSP, HTML, Ajax Technologies 2) Persistence Layer -----...

Singleton class is used for only one instance is created for entire application. One instance and multiple threads."java class Singleton { private static int singleton; pri...

In software engineering, the singleton pattern is a design pattern that restricts the instantiation of a class to one object. This is useful when exactly one object is needed to coordinate actions acr...

public:
default:
private:
protected:

there are 4 access specifiers defined in java.private: who can be accessed within class only.default:who can be accessed within the same package.protected: who can be accessed within the same package ...

Both the tags are used to developing the web pages. HTML tags are static. Where as JSP tags are dynamic.

Differences between HTML and JSP : HTML pages provide Static content with emphasis on the appearance, semantics and layout of the Information in the browser. JSP pages consists of dynamically changi...

Single Inheritance in Java means that a sub class have the capability of inheriting the properties of only one class whereas multiple inheritance is not supported by Java as it increases the complexit...

Single Inheritance: It is sharing only a particular classes Eg: Agents,Proker,join family ......... Multiple Inheritance: It is also sharing with all classes.access specification ...

Static variable, the field is allocated when the class is created. It belongs to the class and not any object of the class. It is class variable. Instance variable, the field is allocated when the c...

class variable is static variable is create when class structure is defined ,and other variables which are create and destroyed with object are called instance variables

Security roles can be applied at application level by either declarative method or programatically. Users or Groups are binded during application deployment by administrator.

final keyword can be applied on:- 1.class 2.member functions(only non-static) 3.data-members(both static and non-static) 4.local variables. 1.by making a class final ,that class cannot be inherited....

Like any variable, a final variable can also be first declared and then assigned a value. But it can be only assigned a value once and only once ( as its final variable ). for example :- final Strin...

Synchronization is a process by using Synchronize keyword to prevent the dead lock. This can be used in methods or block to prevent two threads to access the same resource in the same time.

In this two threads cannot use the same resource simultaneously beacuse the thread execution gets interrupted or terminated hence only a single thread can share resource at a time.

Cloning is the process of creating duplicate copy with current object state. We use this concept in real world like, eg: In Bike manufacturing company, we use cloning for creating same bike object,...

In Java, Cloning is kind of logic to create a copy of the class by implementing Clonable interface.

Java does not support pointer or cannot allow pointers because doing so would allow java programs to breach the firewall between the java execution environment and the host computer

java does not support pointer because of security purpose, as if it have pointer then till easy to find out the addressing of its application which may make it unsecure

The priority of thread can be max,norm and min depending on the underlying os or JMV.

The thread priority levels in terms of integer range from 1 to 10
For max, min & medium priority we have the following:

MAX_PRIORITY  (value=10)
NORM_PRIORITY  (value=5)
MIN_PRIORITY  (value=0)

File extension .xba is a Unknown or unassigned file extension.

Let me tell you where exactly it is used and what it does as per my knowledge.Application library used by OpenOffice.org, an open-source productivity suite; contains the functionality for the componen...

Java soft has declared httpservlet class as an abstract class for its performance, scalability and reusability issues and for security purpose.

Security Purpose

We can use servlet as a shared object by using as shared object the servlet can maintain its state by using its init() and destroy() methods to load and save its state.