Java EE (Java Enterprise Edition) General Discussion

i have an html file in which i m using a text box , for entering amount i m using that text box entry at next jsp. i want to convert amount string into integer for further processing. At next jsp i m using:-

String amount= request.getParameter("bal");
Integer amount1 = Integer.valueOf((String)session.getAttribute("amount"));
and in sql query i m using amount1 as:-
ResultSet rs1 = st.executeQuery("update saving set balance = balance - amount1 where saving.account_no = '" + acc +"'");
my problem is i m getting following error:-
server encountered an internal error and
exception:- numberformat exception
please help me as soon as possible