public synchronized void load() throws IOException {
UpdateSite defaultSite = new UpdateSite("default", config.getUpdateCenterUrl() + "update-center.json");
XmlFile file = getConfigFile();
if(file.exists()) {
try {
sites.replaceBy(((PersistedList)file.unmarshal(sites)).toList());
} catch (IOException e) {
LOGGER.log(Level.WARNING, "Failed to load "+file, e);
}
for (UpdateSite site : sites) {
// replace the legacy site with the new site