hi everybody,
   Remote Reference Layer is using in Remote method 
invocation.when method of one machine execute in one 
machine but run in another machine then it is calledremote 
method invocation.In RMI there is four layers (application 
layer,stub or skelton layer,remote referense 
layer,transportation layer).stub is a client side java 
object and skelton is java object of server side.

The File class is used to create objects that provide access
to the files and directories of a local file system.

public static void main( String[] args )

1. public - declares that the main method is publicly
accessible to other classes

2. static - declares that the main method can be invoked
without creating an instance of the class

3. void - declares that the main method does not return any
value.

4. main - defines the name of the method

5. String[] args - defines a parameter to the main method
which will contain any command line options passed by the
user when invoking the progam.

These command line options will be passed to the program as
an array of string objects.

public-this method is accessible in all the classes
static-this method is called before creation of any instance
void-this method doesn't return any thing
main-Is the name of the method

TextArea and TextField

TextComponent is supperclass for TextArea & TextField.

Container
Label
List
Button
Canvas
Checkbox
Choice
Scrollbar
TextComponent

component-container-panel-applet

primitive type is predefined in java.
byte , int ,short ,long , float , double,boolean and  char
are the  primitive data types used in java.

They are implicitly defined in Java.There are 8 of them and
they are:
boolean,char,byte,short,int,long,float,double

primitive datatypes are the one which will allocate some
memory in the stack.And there are 8 primitive data types
1).byte
2).short
3).int
4).long
5).float
6).double
7).char
8).boolean

Cloneable interface 
Serializable interface

these are called marker interface. 
Interface without any method is called Marker or Null 
Interface

How it is possible without the methods? How it works?

serializable
externalizable

ArrayList, Vector

Connection Pooling it was nothing but a pool of connection
objects to communicate to database.Generally we will create
our own objects for interacting with databases but,in some
times there is a necessary to create more connection objects
even if they not needed that much.So in this times we will
go for connection pooling mechanism.

In this we will create connection pool in application server
and we will store some connection objects to connection pool
When ever the client or user needs to access database then
with help of Intialcontext lookup() method we can reffer to
connection object.

connectin pooling is maintaing a pool of connection which
will allow us to resuse the connection without creating a
new one

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.

useing the jasper reports in java we can genarate the 
reports

jasper reports threw i-report tool

there is jsper reports 
we can use i-report toll which is external from java and by 
using it we can create template and create pdf reports

These are following reports which are supported by java:-

Elixir Report
JasperReports
Crystal-Clear
JReport

I Report is best for Jasper since it creates dynamic width
and height of the table depending on the no. of columns

<input type=file> tag upload file

<input type="file">

No "sizeof" is not a keyword in the Java Programming Language

The Keywords used in Java for getting the size of a string 
or an array is either String.length() or size(), which 
returns a Integer.
sizeOf() is not a keyword!

No it's an unused reserved word

no its command thats return the number of the bytes 
forinstance and its mostlly used in arrays ..i hope u can 
find out more  (but for more its reserved in side c so in 
fact its keyward or command when u write it you will see 
the color blue which means thats reserved keyward) i hope 
its can help ..

sizeof is not a keyword in java it is an operator.

No "null" is not a keyword of the Java Programming Language,
it is a reserved keyword similar to "true" and "false"

no i's a literal

No.It is a Reserved word.We should not use this as an 
identifier.