*
   * <p><b>Discouraged:</b> Prefer using either {@code x -> x == null} or {@code Objects::isNull},
   * but note that lambdas and method references do not have human-readable {@link #toString()}
   * representations and are not serializable.
   */
  public static <T extends @Nullable Object> Predicate<T> isNull() {
    return ObjectPredicate.IS_NULL.withNarrowedType();
  }

  /**

   *
   * <p><b>Discouraged:</b> Prefer using either {@code x -> x == null} or {@code Objects::isNull},
   * but note that lambdas and method references do not have human-readable {@link #toString()}
   * representations and are not serializable.
   */
  public static <T extends @Nullable Object> Predicate<T> isNull() {
    return ObjectPredicate.IS_NULL.withNarrowedType();
  }

  /**

  }

  public void testHigherEntry() {
    assertThat(create().higherEntry("a")).isNull();
  }

  public void testHigherKey() {
    assertThat(create().higherKey("a")).isNull();
  }

  public void testLastEntry() {
    assertThat(create().lastEntry()).isNull();
  }

  public void testLastKey() {
    NavigableMap<String, Integer> map = create();
    map.put("a", 1);

    assertThat(Ints.tryParse("")).isNull();
    assertThat(Ints.tryParse("-")).isNull();
    assertThat(Ints.tryParse("+1")).isNull();
    assertThat(Ints.tryParse("9999999999999999")).isNull();
    assertWithMessage("Max integer + 1")
        .that(Ints.tryParse(Long.toString(((long) GREATEST) + 1)))
        .isNull();
    assertWithMessage("Max integer * 10")

  private static final Object OBJECT = new Object();

  public void testNewReference() throws Exception {
    assertThat(Atomics.newReference().get()).isNull();
  }

  public void testNewReference_withInitialValue() throws Exception {
    assertThat(Atomics.newReference(null).get()).isNull();
    assertEquals(OBJECT, Atomics.newReference(OBJECT).get());
  }

  public void testNewReferenceArray_withLength() throws Exception {

    ValueReference<Object, Object> valueRef = map.newValueReference(entry, value, 1);
    entry.setValueReference(valueRef);

    assertThat(segment.get(key, hash)).isNull();

    // count == 0
    table.set(index, entry);
    assertThat(segment.get(key, hash)).isNull();
    assertThat(segment.containsKey(key, hash)).isFalse();
    assertThat(segment.containsValue(value)).isFalse();

    // count == 1

    ValueReference<Object, Object> valueRef = map.newValueReference(entry, value, 1);
    entry.setValueReference(valueRef);

    assertThat(segment.get(key, hash)).isNull();

    // count == 0
    table.set(index, entry);
    assertThat(segment.get(key, hash)).isNull();
    assertThat(segment.containsKey(key, hash)).isFalse();
    assertThat(segment.containsValue(value)).isFalse();

    // count == 1

    assertThat(map.get(Integer.class)).isNull();
    assertThat(map.getInstance(Integer.class)).isNull();

    map.put(Long.class, null);
    assertThat(map.get(Long.class)).isNull();
    assertThat(map.getInstance(Long.class)).isNull();
  }

  public void testPrimitiveAndWrapper() {
    assertThat(map.getInstance(int.class)).isNull();
    assertThat(map.getInstance(Integer.class)).isNull();

    assertThat(map.containsKey(one)).isFalse();
    assertThat(map.containsValue(one)).isFalse();
    assertThat(map.putIfAbsent(two, three)).isNull();
    assertThat(map.remove(two)).isSameInstanceAs(three);
    assertThat(map.put(three, one)).isNull();
    assertThat(map.put(one, two)).isNull();

    assertThat(map).containsEntry(three, one);
    assertThat(map).containsEntry(one, two);

    assertThat(map.containsKey(one)).isFalse();
    assertThat(map.containsValue(one)).isFalse();
    assertThat(map.putIfAbsent(two, three)).isNull();
    assertThat(map.remove(two)).isSameInstanceAs(three);
    assertThat(map.put(three, one)).isNull();
    assertThat(map.put(one, two)).isNull();

    assertThat(map).containsEntry(three, one);
    assertThat(map).containsEntry(one, two);