Statement s = conn.createStatement();
ResultSet r = s.executeQuery("SELECT COUNT(*) AS rowcount FROM MyTable");
r.next();
int count = r.getInt("rowcount") ;
r.close() ;
System.out.println("MyTable has " + count + " row(s).");

Statement s = conn.createStatement( ResultSet.TYPE_SCROLL_INSENSITIVE, 
   ResultSet.CONCUR_READ_ONLY);
ResultSet r = s.executeQuery
   ("SELECT * FROM employee WHERE id_emp LIKE '1%'");
r.last();
int count = r.getRow();
r.beforeFirst();
...