java - Why do I get an error "The method ... is undefined for the type..."? -

i've build method takes strings input parameter. in index.jsp page, retrieve get-variable url using request.getparameter(). now, want call aforementioned method on string, compiler error saying:

the method <method name>(string) undefined type __2f_<webapp name>_2f_src_2f_main_2f_webapp_2f_index_2e_jsp".

does know why error , how can rid of it. appreciated!

my code rather lengthy, think relevant code:

categorie = request.getparameter("categorie");  if (categorie.equals("")) {     categorie = "category;"; }  arraylist<string> categorieen = querycategories(categorie); 

you calling arraylist<string> categorieen = querycategories(categorie); , did not define querycategories method. since jsp page compiled big servlet class, tries locate querycategories method member of class , not find it.