} catch (RuntimeException tolerated) {
      // GWT's TreeMap.entrySet().removeAll(null) doesn't throws NPE.
    }
  }

  @Override
  public void testEntrySetRetainAllNullFromEmpty() {
    try {
      super.testEntrySetRetainAllNullFromEmpty();
    } catch (RuntimeException tolerated) {
      // GWT's TreeMap.entrySet().retainAll(null) doesn't throws NPE.
    }
  }

  @Override

                NavigableMap<String, String> map = populate(new TreeMap<String, String>(), entries);
                return Collections.checkedNavigableMap(map, String.class, String.class);
              }
            })
        .named("checkedNavigableMap/TreeMap, natural")
        .withFeatures(
            MapFeature.GENERAL_PURPOSE,
            MapFeature.ALLOWS_NULL_VALUES,

    } catch (RuntimeException tolerated) {
      // GWT's TreeMap.entrySet().removeAll(null) doesn't throws NPE.
    }
  }

  @Override
  public void testEntrySetRetainAllNullFromEmpty() {
    try {
      super.testEntrySetRetainAllNullFromEmpty();
    } catch (RuntimeException tolerated) {
      // GWT's TreeMap.entrySet().retainAll(null) doesn't throws NPE.
    }
  }

  @Override

    }

    /**
     * 指定されたキーと値を持つ{@link TreeMap}を構築するための{@literal Maps}を返します。
     *
     * @param <KEY>
     *            <code>Map</code>のキーの型
     * @param <VALUE>
     *            <code>Map</code>の値ーの型
     * @param key
     *            <code>Map</code>に追加されるキー
     * @param value
     *            <code>Map</code>に追加される値
     * @return 指定されたキーと値を持つ{@link TreeMap}を構築するための{@literal Maps}
     */

                SortedMap<String, String> map = populate(new TreeMap<String, String>(), entries);
                return Collections.checkedSortedMap(map, String.class, String.class);
              }
            })
        .named("checkedSortedMap/TreeMap, natural")
        .withFeatures(
            MapFeature.GENERAL_PURPOSE,
            MapFeature.ALLOWS_NULL_VALUES,

  @Override
  protected Table<String, Integer, Character> create(@Nullable Object... data) {
    Supplier<TreeMap<Integer, Character>> factory =
        new Supplier<TreeMap<Integer, Character>>() {
          @Override
          public TreeMap<Integer, Character> get() {
            return Maps.newTreeMap();
          }
        };

  public SafeTreeMap() {
    this(new TreeMap<K, V>());
  }

  public SafeTreeMap(Comparator<? super K> comparator) {
    this(new TreeMap<K, V>(comparator));
  }

  public SafeTreeMap(Map<? extends K, ? extends V> map) {
    this(new TreeMap<K, V>(map));
  }

  public SafeTreeMap(SortedMap<K, ? extends V> map) {
    this(new TreeMap<K, V>(map));
  }

  public SafeTreeMap() {
    this(new TreeMap<K, V>());
  }

  public SafeTreeMap(Comparator<? super K> comparator) {
    this(new TreeMap<K, V>(comparator));
  }

  public SafeTreeMap(Map<? extends K, ? extends V> map) {
    this(new TreeMap<K, V>(map));
  }

  public SafeTreeMap(SortedMap<K, ? extends V> map) {
    this(new TreeMap<K, V>(map));
  }

          {new MapIteratorCache<String, String>(new HashMap<String, String>())},
          {new MapIteratorCache<String, String>(new TreeMap<String, String>(nullsLast))},
          {new MapRetrievalCache<String, String>(new HashMap<String, String>())},
          {new MapRetrievalCache<String, String>(new TreeMap<String, String>(nullsLast))}
        });
  }

  @Before
  public void init() {
    mapCache.clear();
  }

  @Test

          {new MapIteratorCache<String, String>(new HashMap<String, String>())},
          {new MapIteratorCache<String, String>(new TreeMap<String, String>(nullsLast))},
          {new MapRetrievalCache<String, String>(new HashMap<String, String>())},
          {new MapRetrievalCache<String, String>(new TreeMap<String, String>(nullsLast))}
        });
  }

  @Before
  public void init() {
    mapCache.clear();
  }

  @Test