Servlet below shows an example of how to play with cookies.

Java Code:
public class Test4Cookies extends HttpServlet {

  private static final Cookie cookie = new Cookie( "hello" , "world" );
  private static final String paramName = "foo";
  private static final String successURI = "/success.htm";
  private static final String failureURI = "/failure.htm";

  public void doPost(HttpServletRequest req, HttpServletResponse res) {
    if ( req.getParameter( paramName ) == null ) {
       res.addCookie( cookie );
       res.sendRedirect(req.getRequestURI() +"?"+ paramName +"=bar" );
       } 
    else {
       res.sendRedirect
         (( req.getCookies().length == 0 ) ? failureURI : successURI 
       )
    }

  public void doGet(HttpServletRequest req, HttpServletResponse res) {
    doPost(req, res);
    }
}