@NotNull
  @Contract(pure=true)
  public static String[] toStringArray(@Nullable Collection<String> collection) {
    return collection == null || collection.isEmpty()
           ? EMPTY_STRING_ARRAY : collection.toArray(EMPTY_STRING_ARRAY);
  }
@NotNull
  @Contract(pure=true)
  public static String[] toStringArray(@Nullable Collection<String> collection)