> 1)What is the difference  between
> <@ include> & <%jsp:include%>

<@ include> Includes the file at translation (compilation) time,
inserting it into the file as it is built. It becomes part of the
servlet code.

<jsp:include> Includes the OUTPUT of the included file at request
time, and so amounts to being some inserted HTML code.

> 2)In two ways we can crete thread
> 1.Runnable interface
> 2.Thread class
> which one is better & WHY ?

Don't know.
> 3)what is the difference between GEnericservlet &
> HttpServlet ?

HttpServlet is a subclass of GenericServlet and adds the doPost and
doGet methods to handle http requests.

1. the first include is a static include (ie it always includes the same
file) the second is dynamic (ie you can change what gets included at
runtime - say by evaluating some condition to determion which file you
want to include)

2. much the same really - you would use the interface if your class
already extended something else (interfaces are java's way of doing
mutiple inheritance of a sort)

3. HttpServlet adds Http specific stuff - it's what you would use most
of the time.