i have Register page and Login page.And for save usernames and passwords i used arraylists in a servlet.how can i forward these arraylists to another servlet for validate username and passwords..?

by passing them as parameters, no doubt.
do you know how to use the HttpServletRequest and HttpServletResponse?

I think you'll be better of asking any servlet/jsp questions in the webdevelopment>>jsp forum

ok..it can be done by a ServletContext object..thanks for reply.i have another problem.i'll post in jsp forum.