result set = null (sometimes)

hi,

i got a little problem i was pondering about some days now and i still
don't now why it is like that.

i got a class RootAccess through which i would like to get some data
from our DB2/400.

it looks like this:

public class RootAccess
{
        DatabaseMetaData dmd;
        Connection connection;
        ResultSet rs;
        Statement statement;
        String stm;

        public RootAccess()
        {
                try
                {
                        DriverManager.registerDriver(new
AS400JDBCDriver());
                        connection = DriverManager.getConnection
("jdbc:as400://PORTA","user","pwd");
                        dmd = connection.getMetaData();
                        statement = connection.createStatement();
                }
                catch (SQLException sqle)
                { 
                        System.out.println("Problems during database
connection initialization.");
                        System.out.println(sqle.getLocalizedMessage());
                }
        }
                
        public String getCompanyName(int companyID)
        {
                stm = "Select VDDAT from UDVM400DAT.MVDATR where VDSAA =
3 and VDFIR = 10";

                try
                {
                        statement.executeQuery(stm);
                        if(rs != null)
                        {
                                rs.next();
                                return rs.getString(1).trim();
                        }
                        return "";
                }
                catch(SQLException sqle)
                {
                        System.out.println(sqle.getLocalizedMessage());
                        return "";
                }
                finally
                {
                        rs = null;
                }
        }

        public Vector getCompanyNames()
        {
                Vector namesVec = new Vector();
                
                stm = "Select substring(VDDAT,1,20)  from
UDVM400DAT.MVDATR where VDSAA = 3";
                
                try
                {
                        rs = statement.executeQuery(stm);
                        
                        if(rs != null)
                        {
                                while (rs.next())
namesVec.add(rs.getString(1).trim());
                        }               
                }
                catch (SQLException sqle)
                {
                        
                }
                finally
                {
                        rs = null;
                }
                
                return namesVec;
        }
}


my main class looks like this:

public class Test
{
        public static void main(String[] args)
        {
                RootAccess access = new RootAccess();
                
                System.out.println("Firmengruppe 010:" +
access.getCompanyName(10));

                Vector vec = access.getCompanyNames();
                
                for (int i = 0; i < vec.size(); i++)
                {
                        System.out.println("Firmengruppenname:" +
vec.get(i).toString());
                }
        }
}

now my problem:
when i execute the first method, the result set is null. if execute the
same sql statement via several other applications or directly on the
as400 i get the right result (not null).
but when i execute the second method i get the right results.
now why does the first sql request doesn't work. did i forgot something?

os400 v4r5
java (on pc) ibm 1.3.0
jtopen 3.1