Can any one help me, im having a "java.lang.NumberFormatException: null"

Question

im doing a simple servlet and i got this error
"java.lang.NumberFormatException: null"
package process;
* CreateCustomerServlet.java
* Created on July 25, 2007, 10:04 AM
import java.io.*;
import java.net.*;
import javax.annotation.Resource;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
import javax.sql.DataSource;
* @author SLI08
* @version
public class EnrollmentInfoServlet extends HttpServlet {
@Resource(name = "School_system")
private DataSource school_system;
/** Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods.
* @param request servlet request
* @param response servlet response
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String Sch_term = null;
String rmk = null;
int Sch_year = 0;
int enrollmentID = 0;
int i_StudID = 1;
String StudID = request.getParameter("StudentID");
String sts = "";
String msg="";
//validate
Connection conn = null;
PreparedStatement pstmt = null;
try{
i_StudID = Integer.parseInt(StudID);
conn = school_system.getConnection();
pstmt = conn.prepareStatement("SELECT * FROM Enrollment WHERE StudentID=?");
pstmt.setInt(1,i_StudID);
ResultSet rs = pstmt.executeQuery();
while (rs.next()){
enrollmentID=rs.getInt("EnrollmantID");
Sch_year=rs.getInt("SchoolYear");
Sch_term=rs.getString("SchoolTerm");
rmk=rs.getString("Remark");
sts=rs.getString("Status");
HttpSession session = request.getSession();
session.setAttribute("Enrollment",enrollmentID);
session.setAttribute("SchoolYear",Sch_year);
session.setAttribute("SchoolTerm",Sch_term);
session.setAttribute("Remark",rmk);
session.setAttribute("Status",sts);
response.sendRedirect("testdisplay.jsp");
}catch(SQLException ex){
throw new ServletException(ex.getMessage());
}finally{
if(conn!=null) try{conn.close();}catch(SQLException e){}
// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/** Handles the HTTP <code>GET</code> method.
* @param request servlet request
* @param response servlet response
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
/** Handles the HTTP <code>POST</code> method.
* @param request servlet request
* @param response servlet response
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
/** Returns a short description of the servlet.
public String getServletInfo() {
return "Short description";
// </editor-fold>
}

Answer 1

request.getParameter("StudentID");
I think it maybe "null"
test :
if(request.getParameter("StudentID") == null)
System.out.println("yes,it is null");i tried to comment out the "request.getParameter("StudentID")" and i put a default value of "1" which is present in my database and still i got the same error..