static String moveImportsUp(String s) {
  List<String> l = toLines(s);
  List<String> x = new ArrayList<String>();
  Pattern p = Pattern.compile("^\\s*import\\s");
  for (ListIterator<String> i = l.listIterator(); i.hasNext(); ) {
    String line = i.next();
    if (p.matcher(line).find()) {
      x.add(line);
      i.remove();
    }
  }
  x.addAll(l);
  return fromLines(x);
}