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

    @Override
    public @Nullable K floorKey(@ParametricNullness K key) {
      return sortedMap().floorKey(key);
    }

    @Override
    public @Nullable Entry<K, Collection<V>> ceilingEntry(@ParametricNullness K key) {

      return standardLowerKey(key);
    }

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

    @Override
    public @Nullable K floorKey(K key) {
      return standardFloorKey(key);
    }

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

    @Override

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

    @Override
    public @Nullable K floorKey(@ParametricNullness K key) {
      return fromMap().floorKey(key);
    }

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

    @Override

    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())
        .containsExactly(mapEntry("two", 3), mapEntry("three", 5), mapEntry("one", 3))
        .inOrder();

    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())
        .containsExactly(mapEntry("two", 3), mapEntry("three", 5), mapEntry("one", 3))
        .inOrder();