Java - Error en la extraccion de datos

String lunes,martes,miercoles,jueves,viernes,sabado,domingo;

ResultSet rs;

Connection conn;

conn = conexion.getConnection(); //Para tener conexión a la Base de Datos.

String a=(String) jComboBox1.getSelectedItem();

String sql = "SELECT * FROM clases WHERE nombre = '"+a+"'";

try{

Statement stmt = conn.createStatement();

rs=stmt.executeQuery(sql);

rs.beforeFirst();

rs.next();

lunes=rs.getString(5);

martes=rs.getString(6);

miercoles=rs.getString(7);

jueves=rs.getString(8);

viernes=rs.getString(9);

sabado=rs.getString(10);

domingo=rs.getString(11);

String[] lun=lunes.split(",");

String[] mar=martes.split(",");

String[] mier=miercoles.split(",");

String[] jue=jueves.split(",");

String[] vier=viernes.split(",");

String[] sab=sabado.split(",");

String[] dom=domingo.split(",");

jComboBox2.setSelectedItem(lun[0]);

jComboBox3.setSelectedItem(lun[1]);

jComboBox4.setSelectedItem(mar[0]);

jComboBox5.setSelectedItem(mar[1]);

jComboBox6.setSelectedItem(mier[0]);

jComboBox7.setSelectedItem(mier[1]);

jComboBox8.setSelectedItem(jue[0]);

jComboBox9.setSelectedItem(jue[1]);

jComboBox10.setSelectedItem(vier[0]);

jComboBox11.setSelectedItem(vier[1]);

jComboBox12.setSelectedItem(sab[0]);

jComboBox13.setSelectedItem(sab[1]);

jComboBox14.setSelectedItem(dom[0]);

jComboBox15.setSelectedItem(dom[1]);

}catch(Exception e){

    System.out.println(e);

}

if(Lunes.equals("")){

    jComboBox2.SetSelectedItemIndex(0)

    jComboBox2.SetSelectedItemIndex(0)

}else{lunes();}