assert mapFile != null;
assert (mapFile != null);
    public static void addToRecentFiles(String mapFile) {        assert mapFile != null;        // Get the existing recent file list        List recent = getRecentFiles();        // Remove all existing occurences of the file        Iterator iterator = recent.iterator();        while (iterator.hasNext()) {            String filename = (String) iterator.next();            if (filename.equals(mapFile)) {                iterator.remove();            }        }        // Add the given map file to the top        recent.add(0, mapFile);        // Store the new recent file listing        Preferences recentNode = prefs.node("recent");        for (int i = 0; i < RECENT_FILE_COUNT && i < recent.size(); i++)        {            String recentFile = (String) recent.get(i);            recentNode.put("file" + i, recentFile);        }    }