* @return an array of the proper size with {@code null} as the key of the middle element.
   */
  protected Entry<K, V>[] createArrayWithNullKey() {
    Entry<K, V>[] array = createSamplesArray();
    int nullKeyLocation = getNullLocation();
    Entry<K, V> oldEntry = array[nullKeyLocation];
    array[nullKeyLocation] = mapEntry(null, oldEntry.getValue());
    return array;
  }

  /**

    assertEquals(
        "put(present, value) should return the associated value",
        getValueForNullKey(),
        put(newEntry));

    Entry<K, V>[] expected = createArrayWithNullKey();
    expected[getNullLocation()] = newEntry;
    expectContents(expected);
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_KEYS)
  public void testPut_nullKeyUnsupported() {

  @CollectionSize.Require(absent = ZERO)
  public void testFind_nullContained() {
    initCollectionWithNullElement();
    assertEquals(
        getMethodName() + "(null) should return " + getNullLocation(),
        getNullLocation(),
        find(null));
  }

  public void testFind_wrongType() {
    try {
      assertEquals(
          getMethodName() + "(wrongType) should return -1 or throw", -1, find(WrongType.VALUE));

    for (int i = 0; i < getNullLocation(); i++) {
      entries.next();
    }
    return entries.next();
  }

  /**
   * @return an array of the proper size with {@code null} as the value of the middle element.
   */
  protected Entry<K, V>[] createArrayWithNullValue() {
    Entry<K, V>[] array = createSamplesArray();
    int nullValueLocation = getNullLocation();

  @CollectionSize.Require(absent = ZERO)
  public void testFind_nullContained() {
    initCollectionWithNullElement();
    assertEquals(
        getMethodName() + "(null) should return " + getNullLocation(),
        getNullLocation(),
        find(null));
  }

  public void testFind_wrongType() {
    try {
      assertEquals(
          getMethodName() + "(wrongType) should return -1 or throw", -1, find(WrongType.VALUE));

    for (int i = 0; i < getNullLocation(); i++) {
      entries.next();
    }
    return entries.next();
  }

  /**
   * @return an array of the proper size with {@code null} as the value of the middle element.
   */
  protected Entry<K, V>[] createArrayWithNullValue() {
    Entry<K, V>[] array = createSamplesArray();
    int nullValueLocation = getNullLocation();

    assertEquals(
        "put(present, value) should return the associated value",
        getValueForNullKey(),
        put(newEntry));

    Entry<K, V>[] expected = createArrayWithNullKey();
    expected[getNullLocation()] = newEntry;
    expectContents(expected);
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_KEYS)
  public void testPut_nullKeyUnsupported() {

                  assertNull(k);
                  assertEquals(getValueForNullKey(), v);
                  return v3();
                }));

    Entry<K, V>[] expected = createArrayWithNullKey();
    expected[getNullLocation()] = entry(null, v3());
    expectContents(expected);
  }

  @MapFeature.Require({SUPPORTS_PUT, ALLOWS_NULL_KEYS})
  public void testComputeIfPresent_nullKeySupportedAbsent() {
    assertNull(

                  assertNull(k);
                  assertEquals(getValueForNullKey(), v);
                  return v3();
                }));

    Entry<K, V>[] expected = createArrayWithNullKey();
    expected[getNullLocation()] = entry(null, v3());
    expectContents(expected);
  }

  @MapFeature.Require({SUPPORTS_PUT, ALLOWS_NULL_KEYS})
  public void testComputeIfPresent_nullKeySupportedAbsent() {
    assertNull(

  @MapFeature.Require({ALLOWS_NULL_KEYS, ALLOWS_NULL_VALUES})
  @CollectionSize.Require(absent = ZERO)
  public void testCreateWithNullKeyAndValueSupported() {
    Entry<K, V>[] entries = createSamplesArray();
    entries[getNullLocation()] = entry(null, null);
    resetMap(entries);
    expectContents(entries);
  }

  @MapFeature.Require(value = ALLOWS_NULL_KEYS, absent = REJECTS_DUPLICATES_AT_CREATION)
  @CollectionSize.Require(absent = {ZERO, ONE})