Where TableModel stores the columns ordering?

Question

Hi,
In my JTable i allow columns reordering (setReorderingAllowed(true)).
I want to write to a file the new order of the columns and the next time i will run the program, i want to have the columns displayed just like in the file.
Any ideas?
Thanks,
TS

Answer 1

I serialized a trivial TableColumnModel - 8800 bytes! If this is a desktop app, this is the part package java.util.prefs was born to play! A quick example:
import java.awt.*;
import java.awt.event.*;
import java.util.prefs.*;
import javax.swing.*;
import javax.swing.table.*;
public class TablePrefs {
    private static TableModel model = new DefaultTableModel(
        new String[][] {{"a0", "b0", "c0", "d0"}, {"a1", "b1", "c1", "d1"}},
        new String[] {"COLUMN A", "COLUMN B", "COLUMN C", "COLUMN D"});
    public static void main(String[] args) {
        final JTable table = restoreSettings();
        JFrame f = new JFrame("TablePrefs");
        f.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent evt) {
                try {
                    saveSettings(table);
                } catch (BackingStoreException e) {
                    System.err.println(e.getMessage());
                }  finally {
                    System.exit(0);
        f.getContentPane().add(new JScrollPane(table));
        f.pack();
        f.show();
    public static void saveSettings(JTable table) throws BackingStoreException {
        TableColumnModel tcm = table.getColumnModel();
        Preferences node = Preferences.userNodeForPackage(TablePrefs.class);
        for(int i=0, count = tcm.getColumnCount(); i<count; ++i)
            node.putInt("modelIndex"+i, tcm.getColumn(i).getModelIndex());
        node.flush();
    public static JTable restoreSettings() {
         JTable table = new JTable(model);
         TableColumnModel oldtcm = table.getColumnModel();
         TableColumnModel newtcm = new DefaultTableColumnModel();
         int count = oldtcm.getColumnCount();
         Preferences node = Preferences.userNodeForPackage(TablePrefs.class);
         for(int i=0; i<count; ++i) {
            int index = node.getInt("modelIndex"+i, -1);
            if (index == -1)
                break;
            newtcm.addColumn(oldtcm.getColumn(index));
         if (newtcm.getColumnCount() == count)
             table.setColumnModel(newtcm);
         return table;
}Go ahead and run the code! The second execution should retrieve the column ordering from the backing store.