public static Connection getDBConnection(){
        if ( connection == null ) {
            synchronized (DBConnection.class){
                if (connection == null){
                    try {
                        Class.forName(JDBC_DRIVER).newInstance();
                        connection = DriverManager.getConnection(DB_URL, USER, PASS);
                    } catch (ClassNotFoundException e) {
                        e.printStackTrace();
                    } catch (InstantiationException e) {
                        e.printStackTrace();
                    } catch (IllegalAccessException e) {
                        e.printStackTrace();
                    } catch (SQLException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
        return connection;
    }