SortedMap<String, Integer> filtered = Maps.filterEntries(unfiltered, CORRECT_LENGTH);

    assertEquals(ImmutableMap.of("banana", 6), filtered.headMap("dog"));
    assertEquals(ImmutableMap.of(), filtered.headMap("banana"));
    assertEquals(ImmutableMap.of("banana", 6, "dog", 3), filtered.headMap("emu"));

    assertEquals(ImmutableMap.of("banana", 6), filtered.subMap("banana", "dog"));

    SortedMap<String, Integer> filtered = Maps.filterEntries(unfiltered, CORRECT_LENGTH);

    assertEquals(ImmutableMap.of("banana", 6), filtered.headMap("dog"));
    assertEquals(ImmutableMap.of(), filtered.headMap("banana"));
    assertEquals(ImmutableMap.of("banana", 6, "dog", 3), filtered.headMap("emu"));

    assertEquals(ImmutableMap.of("banana", 6), filtered.subMap("banana", "dog"));

    TreeBasedTable<String, Integer, Character> table = makeTable();
    populateTable(table);
    return table.rowMap().headMap("x");
  }

  @Override
  protected Map<String, Map<Integer, Character>> makeEmptyMap() {
    return makeTable().rowMap().headMap("x");
  }

  @Override
  protected String getKeyNotInPopulatedMap() {
    return "z";
  }

    TreeBasedTable<String, Integer, Character> table = makeTable();
    populateTable(table);
    return table.rowMap().headMap("x");
  }

  @Override
  protected Map<String, Map<Integer, Character>> makeEmptyMap() {
    return makeTable().rowMap().headMap("x");
  }

  @Override
  protected String getKeyNotInPopulatedMap() {
    return "z";
  }

    return delegate.get(checkValid(key));
  }

  @Override
  public SortedMap<K, V> headMap(K toKey) {
    return headMap(toKey, false);
  }

  @Override
  public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
    return new SafeTreeMap<>(delegate.headMap(checkValid(toKey), inclusive));
  }

  @Override
  public @Nullable Entry<K, V> higherEntry(K key) {

    return delegate.get(checkValid(key));
  }

  @Override
  public SortedMap<K, V> headMap(K toKey) {
    return headMap(toKey, false);
  }

  @Override
  public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
    return new SafeTreeMap<>(delegate.headMap(checkValid(toKey), inclusive));
  }

  @Override
  public @Nullable Entry<K, V> higherEntry(K key) {

        return tmp;
      }
    }
    return null;
  }

  public ImmutableSortedMap<K, V> headMap(K toKey) {
    checkNotNull(toKey);
    return newView(sortedDelegate.headMap(toKey));
  }

  ImmutableSortedMap<K, V> headMap(K toKey, boolean inclusive) {
    checkNotNull(toKey);
    if (inclusive) {
      K tmp = higher(toKey);
      if (tmp == null) {

  public void testLast() {
    assertEquals(c.getKey(), navigableMap.lastKey());
  }

  @CollectionSize.Require(absent = ZERO)
  public void testHeadMapExclusive() {
    assertFalse(navigableMap.headMap(a.getKey()).containsKey(a.getKey()));
  }

  @CollectionSize.Require(absent = ZERO)
  public void testTailMapInclusive() {
    assertTrue(navigableMap.tailMap(a.getKey()).containsKey(a.getKey()));
  }

  public void testLast() {
    assertEquals(c.getKey(), navigableMap.lastKey());
  }

  @CollectionSize.Require(absent = ZERO)
  public void testHeadMapExclusive() {
    assertFalse(navigableMap.headMap(a.getKey()).containsKey(a.getKey()));
  }

  @CollectionSize.Require(absent = ZERO)
  public void testTailMapInclusive() {
    assertTrue(navigableMap.tailMap(a.getKey()).containsKey(a.getKey()));
  }

      return fromMap().floorKey(key);
    }

    @Override
    public NavigableMap<K, V2> headMap(@ParametricNullness K toKey) {
      return headMap(toKey, false);
    }

    @Override
    public NavigableMap<K, V2> headMap(@ParametricNullness K toKey, boolean inclusive) {
      return transformEntries(fromMap().headMap(toKey, inclusive), transformer);
    }

    @Override
    @CheckForNull