masalah di program java aplikasi netbeans

try {

            String sql = "INSERT INTO tb_jawaban VALUES ('"+txt_nim.getText()+"','" +txt_nama.getText()+"','"+ jawab1+"')";

            java.sql.Connection conn=(Connection)config.configDB();

            java.sql.PreparedStatement pst=conn.prepareStatement(sql);

            pst.execute();

            JOptionPane.showMessageDialog(null, "berhasil disimpan");

        } catch (SQLException e) {

        Logger.getLogger(soalbaru.class.getName()).log(Level.SEVERE, null, e);

        JOptionPane.showMessageDialog(this, e.getMessage());

kenapa salah dibagian configDB nya ya gan..? tolong bantu