static void mapLike syncFilterLinkedListInPlace(O pred, L l) {
  if (l == null) ret;
  synchronized(l) {
    filterListInPlace(pred, l);
  }
}

static <A> void syncFilterLinkedListInPlace(L<A> l, IF1<A, Bool> pred) {
  syncFilterLinkedListInPlace(pred, l);
}