Re: JTabbedPane getSelectedIndex always -1

This is a unit converter I am trying to create. Loadtable is class
that loads the data to create the dropdown list on different tab.
I used for loop to create arrays of panels, which becomes tabs. Also
arrays of buttons, dropdown list.

Now, I need to use submit[i] button to call a function to calculate
the conversion factor. However, I can't define which tab the user has
currently selected. I can do it only within the main method, but not
outside. It would become -1 outside. Please help.

import java.io.FileNotFoundException;
import java.io.IOException;
import javax.swing.*;
import java.awt.BorderLayout;
import java.awt.*;

public class Main {
     JTabbedPane tab = new JTabbedPane();

        int i, index;
        JComboBox[] box = new JComboBox [10];
        JComboBox[] box_2 = new JComboBox [10];
        JTextField[] text = new JTextField[10];
        JTextField[] text_2 = new JTextField[10];
        JPanel [] panel = new JPanel[10];
        JButton[] exit = new JButton[10];
        JButton[] submit = new JButton[10];

    public Main() {
    }

     public static void main(String[] args) throws
FileNotFoundException, IOException {
        JTabbedPane tab = new JTabbedPane();
        int i;
        JComboBox[] box = new JComboBox [10];
        JComboBox[] box_2 = new JComboBox [10];
        JTextField[] text = new JTextField[10];
        JTextField[] text_2 = new JTextField[10];
        JPanel [] panel = new JPanel[10];
        JButton[] exit = new JButton[10];
        JButton[] submit = new JButton[10];

        String [] name = {"Distance",
"Area","Temperature","Speed","Volume",
"Density","Force","Energy","Frequency","Astronomical"};

        loadtable x =new loadtable();
        x.load();
        for (i=0;i<10;i++) {
           panel[i]=new JPanel();
           box[i]= new JComboBox(x.getdata(name[i]));
           box_2[i]=new JComboBox(x.getdata(name[i]));
           text[i]= new JTextField();
           text_2[i]= new JTextField();
           exit[i]=new JButton("Exit");
           submit[i]= new JButton("Submit");
           text[i].setColumns(10);
           text_2[i].setColumns(10);
           panel[i].add(text[i]);
           panel[i].add(box[i]);
           panel[i].add(text_2[i]);
           panel[i].add(box_2[i]);
           panel[i].add(submit[i],BorderLayout.PAGE_END);
           panel[i].add(exit[i],BorderLayout.PAGE_END);
           tab.add(name[i],panel[i]);

        }

        JFrame frame = new JFrame("Unit Converter");
        frame.add(tab);
        frame.setSize(750,200);
        frame.setLocation(200,200);
        frame.setVisible(true);

        for (i=0;i<10;i++) {
            exit[i].addActionListener(new
java.awt.event.ActionListener () {
                public void actionPerformed(java.awt.event.ActionEvent
evt){
                    exitActionPerformed(evt);
                }
            });

        }

         for (i=0;i<10;i++) {
            exit[i].addActionListener(new
java.awt.event.ActionListener () {
                public void actionPerformed(java.awt.event.ActionEvent
evt){
                    exitActionPerformed(evt);
                }
            });

        }

         for (i=0;i<10;i++) {
            submit[i].addActionListener(new
java.awt.event.ActionListener () {
                public void actionPerformed(java.awt.event.ActionEvent
evt){
                    submitActionPerformed(evt);
                }
            });

        }

    }
       private static void
exitActionPerformed(java.awt.event.ActionEvent evt) {
            System.exit(0);
        }

        private static void
submitActionPerformed(java.awt.event.ActionEvent evt) {
            Main x = new Main();
            System.out.println(x.tab.getSelectedIndex());

        }

       }