unexpected output getSelectedIndex method in swing jcombobox

Question

i am using jcombobox from swing and getting some unexpected output from getSelectedIndex method. when i select the 1st JComboBox then the 2nd combobox get enabled and i am using a method getSelectedIndex() which is showing some unexpected output. I mean it should show "0" but it is showing "0" then "-1" then an exception and then finally "0". i can't figure out the cause of exception. I am showing here only part of code hope you guys got me...

    public Tester() {
            super("Utility for publish_date");
            Container contentpane = getContentPane();
            contentpane.setLayout(new BorderLayout());

            try{
            conn = new MyConn().getMyConnection();
             s = conn.createStatement();
             rs = s.executeQuery("select distinct state_name , state_code from state_master where state_code in (select statecode from pdf_detail) order by state_name");
             statelist.add(0,"Select state");
             while(rs.next())
            {
                statelist.add(rs.getString(1));
                statecodelist.add(rs.getString(2));
            }

             System.out.println("the content of statelist"+ statelist);
           System.out.println("the content of statecodelist"+statecodelist);


             list_state  = new String [statelist.size()];
            statelist.toArray(list_state);


            }catch(Exception e)
            {
                System.out.println(e);
                log(e.getMessage());
            }


            combo = new JComboBox(list_state);
            combo.setBounds(50, 50, 100, 20);
            combo.addActionListener(this);


            combo1 = new JComboBox();
            combo1.addActionListener(this);
            combo1.setEnabled(true);

            combo1.setBounds(50, 100, 100, 20);

            combo2 = new JComboBox();
            combo2.addActionListener(this);
            combo2.setEnabled(true);

            combo2.setBounds(50, 100, 100, 20);

            JPanel panel1 = new JPanel(new FlowLayout());
            panel1.add(combo);
            panel1.add(combo1);
            panel1.add(combo2);
            contentpane.add(panel1 , BorderLayout.NORTH);


          label = new JLabel();
          label.setText("Choose publish Date by selecting below.");
          final SimpleDateFormat dateformater = new SimpleDateFormat("yyyy-MM-dd");

        datepicker = new JXDatePicker();
        datepicker.setFormats(dateformater);

        datepicker.addActionListener(new ActionListener(){

                  public void actionPerformed(ActionEvent e)  {
                       //label.setText(datepicker.getDate().toString());
                     System.out.println("new date is "+dateformater.format(datepicker.getDate()));
                    publish_date =    dateformater.format(datepicker.getDate());

                  }
        });



        JPanel panel2 = new JPanel(new FlowLayout());
        panel2.add(label);
        panel2.add(datepicker);
        contentpane.add(panel2 , BorderLayout.CENTER);




            pbutton = new JButton("Submit");
            pbutton.addActionListener(this);

           JPanel panel3 = new JPanel();
           panel3.add(pbutton);
           contentpane.add(panel3 , BorderLayout.SOUTH);


            setSize(600,150);

            setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }



    public void actionPerformed(ActionEvent a) 
    {
        if (a.getSource() == combo) {


            statename = (String)combo.getSelectedItem();
            System.out.println("statename======="+statename);
             q = combo.getSelectedIndex();
        System.out.println("....q....."+q);
            System.out.println(",,,,,,,,,,"+statecodelist.get(q-1));

            try{
                districtcodelist.clear();
                ResultSet rs2 =s.executeQuery("select distinct district_name , district_code from district_master where state_code= '"+statecodelist.get(q-1)+"' AND district_code in (select districtcode from pdf_detail where statecode =  '"+statecodelist.get(q-1)+"') order by district_name ");
                //districtlist.add(0, "Select district");
                while(rs2.next())
                {
                    districtlist.add(rs2.getString(1));
                    districtcodelist.add(rs2.getString(2));

                }

                 System.out.println("the content of districtlist"+ districtlist);
                 System.out.println("the content of districtcodelist"+districtcodelist);


                 list_district  = new String [districtlist.size()];
                 districtlist.toArray(list_district);
            }catch(Exception f)
            {
                 f.printStackTrace();
                 System.out.println(f);
                 log(f.getMessage());

            }
            //combo1.setEnabled(true);
            combo1.removeAllItems();
            for (int i = 0; i < list_district.length; i++) {
                     combo1.removeItem(list_district[i]);
                    combo1.addItem(list_district[i]);

            }
            districtlist.clear();
        }

        else if (a.getSource() == combo1)
        {
           // System.out.println("combo1");
            districtname = (String)combo1.getSelectedItem();
            System.out.println("districtname========"+districtname);
             w = combo1.getSelectedIndex();

             if(w == -1)
             {
                 System.out.println("hre is the prob");
                 System.out.println(combo1.getSelectedItem());
             }
            System.out.println(".....w...."+w);
            System.out.println(combo1.getSelectedItem());
            //System.out.println(",,,,,,,,,,"+districtcodelist.get(w));

            try{
                //tehsillist.add(0,"Select tehsil");


                ResultSet rs3 = s.executeQuery("select distinct tehsil_name , tehsil_code from tehsil_master where state_code= '"+statecodelist.get(q-1)+"' AND district_code='"+districtcodelist.get(w)+"' AND tehsil_code in ( select tehsilcode from pdf_detail where statecode =  '"+statecodelist.get(q-1)+"' AND districtcode = '"+districtcodelist.get(w)+"') order by tehsil_name");

                while(rs3.next())
                {
                    tehsillist.add(rs3.getString(1));
                }


                list_tehsil = new String [tehsillist.size()];
                tehsillist.toArray(list_tehsil);


            }catch(Exception g)
            {
             g.printStackTrace();
             log(g.getMessage());
            System.out.println(g);
        }
            //combo2.setEnabled(true);
            combo2.removeAllItems();
            for (int i = 0; i < list_tehsil.length; i++) {
                combo2.removeItem(list_tehsil[i]);
                combo2.addItem(list_tehsil[i]);
        }
            tehsillist.clear();
        }







        if(a.getSource() == pbutton){
             tehsilname = (String)combo2.getSelectedItem();
             e = combo2.getSelectedIndex();
             System.out.println("....e....."+e);
             System.out.println("....w....."+w);

               if((String)combo.getSelectedItem()== "Select state" || (String)combo1.getSelectedItem()== "Select district" || (String)combo2.getSelectedItem()== "Select tehsil" || publish_date == null  )
               {
                  JOptionPane.showMessageDialog(this, "Select all four items first.");
               }
               else 
               {
                 int c = JOptionPane.showConfirmDialog(this,"Do you really want to continue?","update publish date?",JOptionPane.YES_NO_OPTION);
                   if(c==0)
                   {
                   log("State is "+statename+"  \nDistrict is "+districtname+"  \nTehsil is "+tehsilname);
                  try{


              Properties pr =new Properties();
               pr.load(new FileInputStream("config/config.properties"));
              //String publish_date =  pr.getProperty("publish_date");

              ResultSet rs4 = s.executeQuery("select publish_date from pdf_detail where statecode = (select state_code from state_master where state_name = '"+statename+"') AND districtcode = (select district_code from district_master where district_name = '"+districtname+"') AND tehsilcode = (select tehsil_code from tehsil_master where tehsil_name = '"+tehsilname+"') ");

              while(rs4.next())
              {
                  testvalue = rs4.getString(1);

              }
              if(testvalue != null)
              {


                  n = JOptionPane.showConfirmDialog(this,"Publish_date is already assigned to this tehsil. Do you want to update it?","update publish date?",JOptionPane.YES_NO_OPTION);
                 System.out.println("the value of n is "+n);
              }

              if(testvalue == null ||  n == 0)
              {
                 JOptionPane.showMessageDialog(this, "Publish_date updated");  
                  s.executeUpdate("Update pdf_detail set publish_date = '"+publish_date+"'where statecode=(select state_code from state_master where state_name='"+statename+"') AND districtcode=(select district_code from district_master where district_name='"+districtname+"') AND tehsilcode=(select tehsil_code from tehsil_master where tehsil_name='"+tehsilname+"')");
                  log("publish date of "+tehsilname+" is updated from ("+testvalue+") to ("+publish_date+")");
              }
           }catch(Exception e){
               log(e.getMessage());
               System.out.println(e);}

           if(n==1)
           {
              JOptionPane.showMessageDialog(this, "Pulish_date updation canceled");
              log("publish_date process canceled as it is already done");
           }


          JOptionPane.showMessageDialog(this, "Proces completed");
          log("process completed at");
          log("------------------------------------------------------------------------");
         excelLog();


               }
                   else{
                       setVisible(false);
                     (new Publish_Date()).setVisible(true);

                   }

               }
               }    
    }











    public static void main(String args[]) {
             log("process start time");
            (new Tester()).setVisible(true);
    }

}

OUTPUT:

....q.....1

.....w....0

....q.....1

.....w....-1

java.lang.ArrayIndexOutOfBoundsException: -1
at java.util.ArrayList.get(Unknown Source)
at com.Publish_Date.itemStateChanged(Publish_Date.java:215)
at javax.swing.JComboBox.fireItemStateChanged(Unknown Source)
at javax.swing.JComboBox.selectedItemChanged(Unknown Source)
at javax.swing.JComboBox.contentsChanged(Unknown Source)
at javax.swing.AbstractListModel.fireContentsChanged(Unknown Source)
at javax.swing.DefaultComboBoxModel.setSelectedItem(Unknown Source)
at javax.swing.DefaultComboBoxModel.removeElementAt(Unknown Source)
at javax.swing.DefaultComboBoxModel.removeElement(Unknown Source)
at javax.swing.JComboBox.removeItem(Unknown Source)
at com.Publish_Date.itemStateChanged(Publish_Date.java:190)
at javax.swing.JComboBox.fireItemStateChanged(Unknown Source)
at javax.swing.JComboBox.selectedItemChanged(Unknown Source)
at javax.swing.JComboBox.contentsChanged(Unknown Source)
at javax.swing.AbstractListModel.fireContentsChanged(Unknown Source)
at javax.swing.DefaultComboBoxModel.setSelectedItem(Unknown Source)
at javax.swing.JComboBox.setSelectedItem(Unknown Source)
at javax.swing.JComboBox.setSelectedIndex(Unknown Source)
at javax.swing.plaf.basic.BasicComboPopup$Handler.mouseReleased(Unknown Source)
at java.awt.AWTEventMulticaster.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at javax.swing.plaf.basic.BasicComboPopup$1.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$000(Unknown Source)
at java.awt.EventQueue$1.run(Unknown Source)
at java.awt.EventQueue$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$2.run(Unknown Source)
at java.awt.EventQueue$2.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
java.lang.ArrayIndexOutOfBoundsException: -1

.....w....0

Answer 1

The selected index of a JComboBox is -1 when no item is selected. If an item in the second checkbox is selected and you change the selection in the first one, all items in the second checkbox are removed by combo1.removeAllItems();, which will cause the checkbox to change its selection to -1 and fire an event.

Most likely you can detect the -1 value and just ignore the event or do some cleanup.

Answer 2

Try ActionListener

JComboBox<String> jb =  new JComboBox<String>();

jb.add("Vivek"):
jb.add("Vicky");

jb.addActionListener(new ActionListener() {

    @Override
    public void actionPerformed(ActionEvent arg0) {



        System.out.println(jb.getSelectedIndex());
    }
});