static void centerArrangeWindows(final Window... windows) {
  swing {
    int w = 20*(l(windows)-1);
    for (Window win : windows) w += win.getWidth();
    int x = (screenWidth()-w)/2;
    for (Window win : windows) {
      setFrameLocation(win, x, (screenHeight-win.getHeight())/2);
      x += win.getWidth();
    }
  }
}