SetMultimap<String, Integer> unusedC =
        MultimapBuilder.treeKeys(String.CASE_INSENSITIVE_ORDER)
            .hashSetValues()
            .<String, Integer>build();
  }

  @J2ktIncompatible
  @GwtIncompatible // doesn't build without explicit type parameters on build() methods
  public void testTreeKeys() {
    ListMultimap<String, Integer> multimap = MultimapBuilder.treeKeys().arrayListValues().build();

   * cast to a {@link java.util.SortedMap}.
   */
  @SuppressWarnings("rawtypes")
  public static MultimapBuilderWithKeys<Comparable> treeKeys() {
    return treeKeys(Ordering.natural());
  }

  /**
   * Uses a {@link TreeMap} sorted by the specified comparator to map keys to value collections.
   *

   * cast to a {@link java.util.SortedMap}.
   */
  @SuppressWarnings("rawtypes")
  public static MultimapBuilderWithKeys<Comparable> treeKeys() {
    return treeKeys(Ordering.natural());
  }

  /**
   * Uses a {@link TreeMap} sorted by the specified comparator to map keys to value collections.
   *

   * for a given key in sorted order, but it need not expose the <i>keys</i> in sorted order.
   * Individual {@code SortedSetMultimap} implementations, like those built with {@link
   * MultimapBuilder#treeKeys()}, may make additional guarantees.
   */
  @Override
  Map<K, Collection<V>> asMap();

  /**
   * Returns the comparator that orders the multimap values, with {@code null} indicating that

   *                  str -> str.substring(1),
   *                  MultimapBuilder.treeKeys().arrayListValues()::build));
   *
   * // is equivalent to
   *
   * static final ListMultimap<Character, String> FIRST_LETTER_MULTIMAP;
   *
   * static {
   *     FIRST_LETTER_MULTIMAP = MultimapBuilder.treeKeys().arrayListValues().build();
   *     FIRST_LETTER_MULTIMAP.put('b', "anana");

   *                  str -> str.substring(1),
   *                  MultimapBuilder.treeKeys().arrayListValues()::build));
   *
   * // is equivalent to
   *
   * static final ListMultimap<Character, String> FIRST_LETTER_MULTIMAP;
   *
   * static {
   *     FIRST_LETTER_MULTIMAP = MultimapBuilder.treeKeys().arrayListValues().build();
   *     FIRST_LETTER_MULTIMAP.put('b', "anana");