private void possiblySwitched(ProgressEvent event) {
    final File file = event.getFile();
    if (file == null) return;
    final Url wasUrl = myUrlToCheckForSwitch.get(file);
    if (wasUrl != null && ! wasUrl.equals(event.getURL())) {
      myUrlToCheckForSwitch.remove(file);
      addFileToGroup(FileGroup.SWITCHED_ID, event);
    }
  }
private void possiblySwitched(ProgressEvent event)