*
   * <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();
  }

  /**

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

    map.putInstance(Long.class, null);
    assertTrue(map.containsKey(TypeToken.of(Long.class)));
    assertTrue(map.entrySet().contains(immutableEntry(TypeToken.of(Long.class), null)));
    assertThat(map.get(TypeToken.of(Long.class))).isNull();
    assertThat(map.getInstance(Long.class)).isNull();
  }

    }
  }

  public void testPut() {
    assertThat(table.put("foo", 1, cellValue('a'))).isNull();
    assertThat(table.put("bar", 1, cellValue('b'))).isNull();
    assertThat(table.put("foo", 3, cellValue('c'))).isNull();
    assertEquals((Character) 'a', table.put("foo", 1, cellValue('d')));
    assertEquals((Character) 'd', table.get("foo", 1));

    assertThat(parse(url, "a\u0000b=cd")).isNull()
    assertThat(parse(url, "ab=c\u0000d")).isNull()
    assertThat(parse(url, "a\u0001b=cd")).isNull()
    assertThat(parse(url, "ab=c\u0001d")).isNull()
    assertThat(parse(url, "a\u0009b=cd")).isNull()
    assertThat(parse(url, "ab=c\u0009d")).isNull()
    assertThat(parse(url, "a\u001fb=cd")).isNull()
    assertThat(parse(url, "ab=c\u001fd")).isNull()

    CompactLinkedHashMap<Integer, String> map = CompactLinkedHashMap.create();
    assertThat(map.needsAllocArrays()).isTrue();
    assertThat(map.entries).isNull();
    assertThat(map.keys).isNull();
    assertThat(map.values).isNull();
    assertThat(map.links).isNull();

    map.put(1, Integer.toString(1));
    assertThat(map.needsAllocArrays()).isFalse();
    assertThat(map.entries).hasLength(CompactHashing.DEFAULT_SIZE);

  }

  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