java - Cannot find method symbol -

i don't know if can explain , post proper code make clear, try. have 5 classes. being used check validity of isbn number. getting error "cannot find symbol - method getisbn(). have gui object have instantiated. error comes handler, here:

       public void actionperformed(actionevent e)    {        if (e.getsource()==gui.validatebutton)        {           try           {             gui.isbntext.getisbn();/////////////error//////////             gui.status.settext("isbn " + isbntext.booknum + " valid");           }           catch(isbnexception er)           {             gui.status.settext(er.getmessage());               }        }       else system.exit(0); 

i wont post code gui, idea: theres gui, has textfield called isbntext, , in isbntext class, there method retrieve text, called getisbn, code:

    public isbntext()  {     super(20); }   //retrieve isbn num textfield public string getisbn() throws isbnexception {                booknum = gettext();         validateisbn(booknum);     return booknum;       } 

i hope enough, not much, go on. ideas?

without seeing gui class, it's difficult say. suspect isbntext field declared :

jtextfield isbntext = new isbntext(); 

if that's case, getisbn() can't found because variable's declared type jtextfield, , not isbntext. need change

isbntext isbntext = new isbntext(); 

note public variables should never used, , variables in java should start lower-case letter. should call isbntext rather isbntext.