static <A> LinkedHashSet<A> asLinkedHashSet(A[] array) {
  new LinkedHashSet<A> set;
  for (A o : array)
    if (o != null)
      set.add(o);
  ret set;
}

static <A> LinkedHashSet<A> asLinkedHashSet(Collection<A> l) {
  if (l instanceof LinkedHashSet) ret (LinkedHashSet) l;
  new LinkedHashSet<A> set;
  for (A o : l)
    if (o != null)
      set.add(o);
  ret set;
}

Began life as a copy of #1001899