> i have got one question
Are you sure? I demand a recount!
> can we call destroy method from service method?
http://www.codestyle.org/java/servlets/faq-Lifecycle.shtml#destroyservice
> and can we have constructor in servlet?
http://www.codestyle.org/java/servlets/faq-Lifecycle.shtml#constructlifecycle

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being a class I assume you could, however I don't know how that would
affect the program.