vediamo se ho capito:
codice:
public class DBManager {

    private static DBManager instance = null;
    final static String HOST = "";
    final static String DB = "";
    final static String USER = "";
    final static String PWD = "";
    private static Connection conn = null;

    private DBManager() {
    }

    public static DBManager getInstance() {
        return (instance == null) ? (instance = new DBManager()) : instance;
    }

    public Connection getConnection() throws ClassNotFoundException, SQLException {
        Class.forName("com.mysql.jdbc.Driver");
        conn = DriverManager.getConnection("jdbc:mysql://" + HOST + ":3306/" + DB + "?user=" + USER + "&password=" + PWD);
        return conn;
    }

    public void select() throws ClassNotFoundException, SQLException {
        conn = DBManager.getInstance().getConnection();
        Statement stmt = conn.createStatement();
        ResultSet rs = stmt.executeQuery("SELECT * FROM bookv");
        while (rs.next()) {
            String id = rs.getString("book_id");
            String name = rs.getString("name");
            String author = rs.getString("author_name");
            String editor = rs.getString("editor_name");
            String price = rs.getString("price");
            String isbn = rs.getString("isbn");
            String note = rs.getString("note");
            Object[] riga = {id, name, author, editor, price, isbn, note};
            ((DefaultTableModel) Main.getTable().getModel()).addRow(riga);
        }
        rs.close();
        stmt.close();
    }
// altri metodi nn statici
}
poi ad esempio nel mio JFrame:
codice:
public class Main extends javax.swing.JFrame {

    private DBManager dbman = DBManager.getInstance();

........

dbman.select();
così istanzio una volta la classe e poi richiamo i vari metodi dove mi servono.