SortedMap<K, V> delegate = newModifiableDelegate(comparator);
    for (Entry<? extends K, ? extends V> entry : map.entrySet()) {
      putEntryWithChecks(delegate, entry);
    }
    return newView(unmodifiableSortedMap(delegate), comparator);
  }

  private static <K, V> void putEntryWithChecks(
      SortedMap<K, V> map, Entry<? extends K, ? extends V> entry) {
    K key = checkNotNull(entry.getKey());