source: josm/src/org/openstreetmap/josm/gui/preferences/AdvancedPreference.java@ 171

package org.openstreetmap.josm.gui.preferences;

import static org.openstreetmap.josm.tools.I18n.tr;

import java.awt.Dimension;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.Map;
import java.util.TreeSet;
import java.util.Map.Entry;

import javax.swing.Box;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.table.DefaultTableModel;

import org.openstreetmap.josm.Main;
import org.openstreetmap.josm.tools.GBC;

public class AdvancedPreference implements PreferenceSetting {

        private Map<String,String> orig;
        private DefaultTableModel model;

        public void addGui(final PreferenceDialog gui) {
                JPanel p = gui.createPreferenceTab("advanced", tr("Advanced Preferences"), tr("Setting Preference entries directly. Use with caution!"));

                model = new DefaultTableModel(new String[]{"Key", "Value"},0) {
                        @Override public boolean isCellEditable(int row, int column) {
                                return column != 0;
                        }
                };
                final JTable list = new JTable(model);
                JScrollPane scroll = new JScrollPane(list);
                p.add(scroll, GBC.eol().fill(GBC.BOTH));
                scroll.setPreferredSize(new Dimension(400,200));

                orig = Main.pref.getAllPrefix("");
                orig.remove("osm-server.password");

                for (String s : new TreeSet<String>(orig.keySet()))
                        model.addRow(new String[]{s, Main.pref.get(s)});

                JButton add = new JButton(tr("Add"));
                p.add(Box.createHorizontalGlue(), GBC.std().fill(GBC.HORIZONTAL));
                p.add(add, GBC.std().insets(0,5,0,0));
                add.addActionListener(new ActionListener(){
                        public void actionPerformed(ActionEvent e) {
                                JPanel p = new JPanel(new GridBagLayout());
                                p.add(new JLabel("Key"), GBC.std().insets(0,0,5,0));
                                JTextField key = new JTextField(10);
                                JTextField value = new JTextField(10);
                                p.add(key, GBC.eop().insets(5,0,0,0).fill(GBC.HORIZONTAL));
                                p.add(new JLabel("Value"), GBC.std().insets(0,0,5,0));
                                p.add(value, GBC.eol().insets(5,0,0,0).fill(GBC.HORIZONTAL));
                                int answer = JOptionPane.showConfirmDialog(gui, p, tr("Enter a new key/value pair"), JOptionPane.OK_CANCEL_OPTION);
                                if (answer == JOptionPane.OK_OPTION)
                                        model.addRow(new String[]{key.getText(), value.getText()});
                        }
                });

                JButton edit = new JButton(tr("Edit"));
                p.add(edit, GBC.std().insets(5,5,5,0));
                edit.addActionListener(new ActionListener(){
                        public void actionPerformed(ActionEvent e) {
                                edit(gui, list);
                        }
                });

                JButton delete = new JButton(tr("Delete"));
                p.add(delete, GBC.std().insets(0,5,0,0));
                delete.addActionListener(new ActionListener(){
                        public void actionPerformed(ActionEvent e) {
                                if (list.getSelectedRowCount() == 0) {
                                        JOptionPane.showMessageDialog(gui, tr("Please select the row to delete."));
                                        return;
                                }
                                while (list.getSelectedRow() != -1)
                                        model.removeRow(list.getSelectedRow());
                        }
                });

                list.addMouseListener(new MouseAdapter(){
                        @Override public void mouseClicked(MouseEvent e) {
                                if (e.getClickCount() == 2)
                                        edit(gui, list);
                        }
                });
        }

        public void ok() {
                for (int i = 0; i < model.getRowCount(); ++i) {
                        String key = model.getValueAt(i,0).toString();
                        String value = model.getValueAt(i,1).toString();
                        String origValue = orig.get(key);
                        if (origValue == null || !origValue.equals(value))
                                Main.pref.put(key, value);
                        orig.remove(key); // processed.
                }
                for (Entry<String, String> e : orig.entrySet())
                        Main.pref.put(e.getKey(), null);
        }


        private void edit(final PreferenceDialog gui, final JTable list) {
                if (list.getSelectedRowCount() != 1) {
                        JOptionPane.showMessageDialog(gui, tr("Please select the row to edit."));
                        return;
                }
                String v = JOptionPane.showInputDialog(tr("New value for {0}", model.getValueAt(list.getSelectedRow(), 0)), model.getValueAt(list.getSelectedRow(), 1));
                if (v != null)
                        model.setValueAt(v, list.getSelectedRow(), 1);
        }
}