String st = "Select Gen_Id(Gen,1) from Rdb$DataBase";
            CallableStatement stmt = this.getDBTransaction().createCallableStatement(st, 0);
                int id;
                try {
                    stmt.execute();
                    id = stmt.getInt(1);
                } catch (SQLException e) {
                    System.out.println(e);
                    id = 0;
                }

org.firebirdsql.jdbc.FBSQLException: GDS Exception. 335544569. Dynamic SQL Error
SQL error code = -104
Token unknown - line 1, column 38
fromRdb$DataBase