Select Max and ResultSet Problem With Access

Question

The following code is producing a 'null pointer excepetion' error and I know why it is occurring I just do not know how to fix the problem.
Basically I want to automitically generate a unique ID that is one number higher than the max ID (data is stored within an Access database). The ID field is made up of first and last initial taken from parsing previous login info ('JS-01', 'JS-02', ect.). If there are no IDs in the database that match your login info I want to set the new ID equal to 'JS-01' if your login is 'James Smith' for example.
The problem is explained within the code below.
<%
//define resultset and statement
ResultSet rss=null;
ResultSet rs=null;
Statement stmt=null;
//HERE IS WHERE YOU PARSE THE LOGIN INFO
String finitial = (String)session.getAttribute("vfirst");//vfirst=JIM
String linitial = (String)session.getAttribute("vlast");//vlast=SMITH
char f = finitial.charAt(0);
char n = linitial.charAt(0);
String sID = f+""+n;//NOW sID CONTAINS 'JS'
try {
//Using the current database connection create a statement
stmt=con.createStatement();
//QUERY TO SELECT MAX ID
//NOTE: CURRENTLY THERE ARE NO IDs LIKE 'JS' IN THE DATABASE !!!!!!
String sql="SELECT Max(ID) As MaxID FROM tblError Where ID LIKE '%"+sID+"%'" ;
rs = stmt.executeQuery(sql);
String newID;
//HERE THE RESULT SET SHOULD BE NULL BUT IT IS NOT. I KNOW THIS BECAUSE WHEN I REPLACE String iID WITH A LITERAL LIKE 'JS-03' THE LOGIC WILL EXECUTE CORRECTLY AND GIVE ME 'JS-04'. IF I LEAVE THE CODE LIKE IT IS THEN I GET THE NULL POINTER VALUE ERROR BECAUSE YOU CANNOT RESOLVE "MaxID" WHEN THE RESULT SET IS NULL. IF THE RESULT SET IS NULL IT SHOULD NOT EVEN EXECUTE ANY OF THIS CODE WITHIN THE 'if' STATEMENT, BUT IT IS. SO BASICALLY JSP IS LEAVING ME WITH A MAJOR OXYMORON AND I WOULD APPRECIATE ANY ADVICE THAT WOULD HELP ME SOLVE THIS PROBLEM.
if(rs.next()){
String iID = rs.getString("MaxID");
String letters = iID.substring(0,3);
int numbers = Integer.parseInt(iID.substring(3,5));
numbers = numbers + 1;
if(numbers < 10){
newID = letters + "0" + numbers;}
else{
newID = letters + numbers;
else{//IF THERE IS NO RESULT SET THAN THE ID SHOULD BE 'JS-01'
newID = sID + "-01";
%>
Because this an Access database I cannot use any null exception functions such as NVL or COALESCE which are specific to Oracle and SQL Server I beleive.

Answer 1

The max() will return a result set, even if the max value is null.
You should check to see if iID is null.
if(rs.next())
   String iID = rs.getString("MaxID");
   if (iID == null)
       newID = sID + "-01";
   else
      String letters = iID.substring(0,3);
      ... etc ...
}