Sorry for the post flame, but I thought the list was indeed getting a
bit sparse

I finished my last post showing that the error occurs in a
while(rs.next()) {} structure
I realized the insides of that structure may help too:

while(rs.next()) {
long id=rs.getLong(1);
MyClass dg=new MyClass(id,rs.getString(2));
query="select a,b,c from d where a="+id;
Statement st2=conn.createStatement();
rs2=st2.executeQuery(query);
while(rs2.next()) {
long id2=rs2.getLong(1);
doSomeThing(new MyClass2(id2,id,rs2.getString(2),rs2.getLong(3)));
}
rs2.close(); st2.close();
}
rs.close();

Cheerio