private static void merge(int offset, CopyOnWriteList source, CopyOnWriteList @NotNull [] target) {
    if (source != null) {
      CopyOnWriteList existing = target[offset];
      target[offset] = existing == null ? source : existing.addAll(source);
    }
  }
private static void merge(int offset, CopyOnWriteList source, CopyOnWriteList @NotNull [] target)