source: josm/src/org/openstreetmap/josm/io/RawGpsReader.java@ 103

package org.openstreetmap.josm.io;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Collection;
import java.util.LinkedList;

import org.openstreetmap.josm.data.coor.LatLon;
import org.openstreetmap.josm.gui.layer.RawGpsLayer.GpsPoint;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;

import uk.co.wilson.xml.MinML2;

/**
 * Read raw gps data from a gpx file. Only way points with their ways segments
 * and waypoints are imported.
 * @author imi
 */
public class RawGpsReader {

        private static class Parser extends MinML2 {
                /**
                 * Current track to be read. The last entry is the current trkpt.
                 * If in wpt-mode, it contain only one GpsPoint.
                 */
                private Collection<GpsPoint> current = new LinkedList<GpsPoint>();
                public Collection<Collection<GpsPoint>> data = new LinkedList<Collection<GpsPoint>>();
                private LatLon currentLatLon;
                private String currentTime;

                @Override public void startElement(String namespaceURI, String localName, String qName, Attributes atts) throws SAXException {
                        if (qName.equals("wpt") || qName.equals("trkpt")) {
                                try {
                        double lat = Double.parseDouble(atts.getValue("lat"));
                        double lon = Double.parseDouble(atts.getValue("lon"));
                                if (Math.abs(lat) > 90)
                                        throw new SAXException("Data error: lat value '"+lat+"' is out of bound.");
                                if (Math.abs(lon) > 180)
                                        throw new SAXException("Data error: lon value '"+lon+"' is out of bound.");
                        currentLatLon = new LatLon(lat, lon);
                } catch (NumberFormatException e) {
                        e.printStackTrace();
                        throw new SAXException(e);
                }
                        } else if (qName.equals("time")) {
                                currentTime = "";
                        }
                }

                @Override public void characters(char[] ch, int start, int length) {
                        if (currentTime != null && currentTime.equals(""))
                                currentTime = new String(ch, start, length);
                }

                @Override public void endElement(String namespaceURI, String localName, String qName) {
                        if (qName.equals("wpt") || qName.equals("trkpt")) {
                                current.add(new GpsPoint(currentLatLon, currentTime));
                        } else if (qName.equals("trkseg") || qName.equals("trk") || qName.equals("gpx"))
                                newTrack();
        }

                private void newTrack() {
                        if (!current.isEmpty()) {
                                data.add(current);
                                current = new LinkedList<GpsPoint>();
                        }
                }
        }

        /**
         * Parse and return the read data
         */
        public static Collection<Collection<GpsPoint>> parse(InputStream source) throws SAXException, IOException {
                Parser parser = new Parser();
                parser.parse(new InputStreamReader(source, "UTF-8"));
                return parser.data;
        }
}