}

  @Override
  @CheckForNull
  public Entry<K, V> higherEntry(@ParametricNullness K key) {
    return tailMap(key, false).firstEntry();
  }

  @Override
  @CheckForNull
  public K lowerKey(@ParametricNullness K key) {
    return Maps.keyOrNull(lowerEntry(key));
  }

  @Override
  @CheckForNull
  public K floorKey(@ParametricNullness K key) {
    return Maps.keyOrNull(floorEntry(key));
  }

      return standardSubMap(fromKey, toKey);
    }

    @Override
    public @Nullable Entry<K, V> lowerEntry(K key) {
      return standardLowerEntry(key);
    }

    @Override
    public @Nullable K lowerKey(K key) {
      return standardLowerKey(key);
    }

    @Override
    public @Nullable Entry<K, V> floorEntry(K key) {
      return standardFloorEntry(key);
    }

    @Override

      Entry<K, Collection<V>> entry = sortedMap().lowerEntry(key);
      return (entry == null) ? null : wrapEntry(entry);
    }

    @Override
    @CheckForNull
    public K lowerKey(@ParametricNullness K key) {
      return sortedMap().lowerKey(key);
    }

    @Override
    @CheckForNull
    public Entry<K, Collection<V>> floorEntry(@ParametricNullness K key) {

      Entry<K, Collection<V>> entry = sortedMap().lowerEntry(key);
      return (entry == null) ? null : wrapEntry(entry);
    }

    @Override
    @CheckForNull
    public K lowerKey(@ParametricNullness K key) {
      return sortedMap().lowerKey(key);
    }

    @Override
    @CheckForNull
    public Entry<K, Collection<V>> floorEntry(@ParametricNullness K key) {

    public Entry<K, V2> lowerEntry(@ParametricNullness K key) {
      return transformEntry(fromMap().lowerEntry(key));
    }

    @Override
    @CheckForNull
    public K lowerKey(@ParametricNullness K key) {
      return fromMap().lowerKey(key);
    }

    @Override
    public NavigableSet<K> navigableKeySet() {
      return fromMap().navigableKeySet();
    }

    @Override
    @CheckForNull

        return nullableSynchronizedEntry(delegate().lowerEntry(key), mutex);
      }
    }

    @Override
    @CheckForNull
    public K lowerKey(K key) {
      synchronized (mutex) {
        return delegate().lowerKey(key);
      }
    }

    @Override
    public Set<K> keySet() {
      return navigableKeySet();
    }

    assertEquals("one", map.ceilingKey("one"));
    assertEquals(mapEntry("three", 5), map.higherEntry("one"));
    assertEquals(mapEntry("one", 3), map.ceilingEntry("one"));
    assertEquals("one", map.lowerKey("three"));
    assertEquals("one", map.lowerKey("r"));
    assertEquals("one", map.floorKey("r"));
    assertEquals("three", map.floorKey("three"));

    assertThat(map.descendingMap().entrySet())

    assertEquals("one", map.ceilingKey("one"));
    assertEquals(mapEntry("three", 5), map.higherEntry("one"));
    assertEquals(mapEntry("one", 3), map.ceilingEntry("one"));
    assertEquals("one", map.lowerKey("three"));
    assertEquals("one", map.lowerKey("r"));
    assertEquals("one", map.floorKey("r"));
    assertEquals("three", map.floorKey("three"));

    assertThat(map.descendingMap().entrySet())

  }

  @Override
  @CheckForNull
  public Entry<K, V> lowerEntry(K key) {
    return headMap(key, false).lastEntry();
  }

  @Override
  @CheckForNull
  public K lowerKey(K key) {
    return keyOrNull(lowerEntry(key));
  }

  @Override
  @CheckForNull
  public Entry<K, V> floorEntry(K key) {
    return headMap(key, true).lastEntry();
  }

  @Override

  }

  @Override
  @CheckForNull
  public Entry<K, V> lowerEntry(K key) {
    return headMap(key, false).lastEntry();
  }

  @Override
  @CheckForNull
  public K lowerKey(K key) {
    return keyOrNull(lowerEntry(key));
  }

  @Override
  @CheckForNull
  public Entry<K, V> floorEntry(K key) {
    return headMap(key, true).lastEntry();
  }

  @Override