source: josm/src/org/openstreetmap/josm/actions/SaveGpxAction.java@ 16

package org.openstreetmap.josm.actions;

import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

import javax.swing.AbstractAction;
import javax.swing.ImageIcon;
import javax.swing.JFileChooser;
import javax.swing.JOptionPane;

import org.openstreetmap.josm.gui.Main;
import org.openstreetmap.josm.io.GpxWriter;

/**
 * Export the current selected window's DataSet as gpx values. Remember, that some 
 * information could be lost. If so, an information message will ask the user to proceed.
 * (Means, if all information can be saved, no warning message appears).
 *  
 * @author imi
 */
public class SaveGpxAction extends AbstractAction {

        /**
         * Construct the action with "Save GPX" as label.
         */
        public SaveGpxAction() {
                super("Save GPX", new ImageIcon(Main.class.getResource("/images/savegpx.png")));
                putValue(MNEMONIC_KEY, KeyEvent.VK_S);
        }
        
        @SuppressWarnings("unchecked")
        public void actionPerformed(ActionEvent event) {
                if (Main.main.getMapFrame() == null) {
                        JOptionPane.showMessageDialog(Main.main, "No document open so nothing to save.");
                        return;
                }
                JFileChooser fc = new JFileChooser("data");
                fc.showSaveDialog(Main.main);
                File gpxFile = fc.getSelectedFile();
                if (gpxFile == null)
                        return;
                
                try {
                        FileWriter fileWriter = new FileWriter(gpxFile);
                        GpxWriter out = new GpxWriter(fileWriter, Main.main.getMapFrame().mapView.dataSet);
                        out.output();
                        fileWriter.close();
                } catch (IOException e) {
                        e.printStackTrace();
                        JOptionPane.showMessageDialog(Main.main, "An error occoured while saving.\n"+e.getMessage());
                }
        }

}