static String moveImportsUp2(String s) {
  List<String> l = toLines(s);
  Pattern p = Pattern.compile("^\\s*import\\s");
  
  // Count import statements on top
  int iStart = 0;
  while (iStart < l(l) && p.matcher(l.get(iStart)).find())
    ++iStart;
 
  // Find import statements in rest
  L<S> l2 = subList(l, iStart);
  new L<S> x;
  ListIterator<String> i = l2.listIterator();
  while (i.hasNext()) {
    S line = i.next();
    if (p.matcher(line).find()) {
      x.add(line);
      i.remove();
    }
  }
  
  // Return null or changed version
  if (isEmpty(x)) ret null;
  return fromLines(concatLists(subList(l, 0, iStart), x, l2));
}

Began life as a copy of #1000608