source: josm/src/org/openstreetmap/josm/data/Preferences.java@ 77

package org.openstreetmap.josm.data;

import java.awt.Color;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Map;
import java.util.SortedMap;
import java.util.TreeMap;
import java.util.Map.Entry;

import org.openstreetmap.josm.data.osm.visitor.SimplePaintVisitor;
import org.openstreetmap.josm.tools.ColorHelper;


/**
 * This class holds all preferences for JOSM.
 * 
 * Other classes can register their beloved properties here. All properties will be
 * saved upon set-access.
 * 
 * @author imi
 */
public class Preferences {

        public static interface PreferenceChangedListener {
                void preferenceChanged(String key, String newValue);
        }
        
        ArrayList<PreferenceChangedListener> listener = new ArrayList<PreferenceChangedListener>();
        
        /**
         * Map the property name to the property object.
         */
        private SortedMap<String, String> properties = new TreeMap<String, String>();
        
        /**
         * Return the location of the preferences file
         */
        public static String getPreferencesDir() {
                return System.getProperty("user.home")+"/.josm/";
        }


        public void addPreferenceChangedListener(PreferenceChangedListener listener) {
                this.listener.add(listener);
        }
        public void removePreferenceChangedListener(PreferenceChangedListener listener) {
                this.listener.remove(listener);
        }


        synchronized public String get(String key) {
                if (!properties.containsKey(key))
                        return "";
                return properties.get(key);
        }
        synchronized public String get(String key, String def) {
                String prop = properties.get(key);
                if (prop == null || prop.equals(""))
                        return def;
                return prop;
        }
        synchronized public Map<String, String> getAllPrefix(String prefix) {
                Map<String,String> all = new TreeMap<String,String>();
                for (Entry<String,String> e : properties.entrySet())
                        if (e.getKey().startsWith(prefix))
                                all.put(e.getKey(), e.getValue());
                return all;
        }
        synchronized public boolean getBoolean(String key) {
                return properties.containsKey(key) ? Boolean.parseBoolean(properties.get(key)) : false;
        }


        synchronized public void put(String key, String value) {
                if (value == null)
                        properties.remove(key);
                else
                        properties.put(key, value);
                save();
                firePreferenceChanged(key, value);
        }
        synchronized public void put(String key, boolean value) {
                properties.put(key, Boolean.toString(value));
                save();
                firePreferenceChanged(key, Boolean.toString(value));
        }

        private void firePreferenceChanged(String key, String value) {
                for (PreferenceChangedListener l : listener)
                        l.preferenceChanged(key, value);
        }


        /**
         * Called after every put. In case of a problem, do nothing but output the error
         * in log.
         */
        private void save() {
                try {
                        PrintWriter out = new PrintWriter(new FileWriter(
                                        getPreferencesDir() + "preferences"));
                        for (Entry<String, String> e : properties.entrySet())
                                if (!e.getValue().equals(""))
                                        out.println(e.getKey() + "=" + e.getValue());
                        out.close();
                } catch (IOException e) {
                        e.printStackTrace();
                        // do not message anything, since this can be called from strange
                        // places.
                }               
        }


        public void load() throws IOException {
                properties.clear();
                BufferedReader in = new BufferedReader(new FileReader(getPreferencesDir()+"preferences"));
                int lineNumber = 0;
                for (String line = in.readLine(); line != null; line = in.readLine(), lineNumber++) {
                        int i = line.indexOf('=');
                        if (i == -1 || i == 0)
                                throw new IOException("Malformed config file at line "+lineNumber);
                        properties.put(line.substring(0,i), line.substring(i+1));
                }
        }

        public void resetToDefault() {
                properties.clear();
                properties.put("laf", "javax.swing.plaf.metal.MetalLookAndFeel");
                properties.put("projection", "org.openstreetmap.josm.data.projection.Epsg4263");
                properties.put("osm-server.url", "http://www.openstreetmap.org/api");
                properties.put("color.node", ColorHelper.color2html(Color.red));
                properties.put("color.segment", ColorHelper.color2html(SimplePaintVisitor.darkgreen));
                properties.put("color.way", ColorHelper.color2html(SimplePaintVisitor.darkblue));
                properties.put("color.incomplete way", ColorHelper.color2html(SimplePaintVisitor.darkerblue));
                properties.put("color.selected", ColorHelper.color2html(Color.white));
                properties.put("color.gps point", ColorHelper.color2html(Color.gray));
                save();
        }
}