Question { 7565 }

Explain Connection Pooling?

Answer

the most time consuming process when we work with a
database is to create a connection object. when application
goes out of scope the object becomes a candidate for
grabage collector. every time we create and every it will
be destroyed. this as effect on a distributed application,
where n no clients are waiting for the response. Connection
pooling is a concept of object reusability.This is a
service provided by application servers.

Question { 6657 }

What is static and a non-static inner class?

Answer

non static inner classes can access all the members of the
outer class i.e both static and nonstatic members.In
nonstatic inner classes we cannot have static declarations
done.To access non static inner class members we outer
class reference.

static inner classes can access only static members of the
outer class.In static inner class we can have static
declarations done. To access static inner class members
no need of outer class reference.

Question { Satyam, 8037 }

what is mean by method signature?

Answer

It consists of method name and type of the parameters

void sum(int a,int b){}

sum(int,int) is the method signature

In a class we cannot have two methods with the same method
signature

Question { Amdocs, 6494 }

what is difference between servletconfig and servletcontext?

Answer

ServletConfig and ServletContext are interfaces in
javax.servlet package
ServletConfig is one per one Servlet.Each servlet as its
own ServletConfig object.The ServletConfig object is
provided by the Container during the initialization phase
of the Servlet.ServletConfig object can be user to read
initialization parameters into the Servlet from web.xml.

ServletContext is one per one web-application.All servlets
which are in a web-application have common ServletContext.
ServletContext can be used to communicate the Servlet with
the ServletContainer.It can also be used to read
initialization parameters from web.xml.It can be used to
share some resources between servlets which are in a web-
application.(resources like Connection object)

Question { Accenture, 35760 }

define System.out.println(); what is the meaning!

Answer

System is class in java.lang package

out is a static member of type PrinStream class(java.io)
declared in the System class.static members of a class can
be accessed directly by classname that's why System.out.

println is a method in PrintStream class.out is of type
PrintStream that's why you access println w.r.t out.

why this big statement? because here no need to import any
package, like you include a header file in c or
c++.java.lang is the default package.

Question { GCPL, 5170 }

what is mean by synchronization?

Answer

Synchronization is a process of accessing a shared resource in a multithreaded environment by one thread at a time.

Generally in Multithreaded applications all the threads start execution at a time(i.e doing multiple task at a time) . In this situation we need a piece of code to used by one thread at a time then we need to use Synchronization.

When a thread access a Synchronized code it establishes lock with that code and all the other threads will be there in waiting state. The Lock will be released once the thread as finished it task and other thread waiting will acquire the lock.