static <A, B extends A> void addAllNonNulls(Collection<A> c, Iterable<B> b) {
  if (c != null && b != null) for (A a : b) if (a != null) c.add(a);
}

static <A, B extends A> void addAllNonNulls(Collection<A> c, B... b) {
  if (c != null && b != null) for (A a : b) if (a != null) c.add(a);
}