assertTrue(multimap().remove(getKeyForNullValue(), null));

    expectMissing(mapEntry(getKeyForNullValue(), (V) null));
    assertGet(getKeyForNullValue(), ImmutableList.<V>of());
  }

  @MapFeature.Require({SUPPORTS_REMOVE, ALLOWS_NULL_KEY_QUERIES})
  public void testRemoveNullKeyAbsent() {
    assertFalse(multimap().remove(null, v0()));
    expectUnchanged();
  }

    assertTrue(multimap().remove(getKeyForNullValue(), null));

    expectMissing(mapEntry(getKeyForNullValue(), (V) null));
    assertGet(getKeyForNullValue(), ImmutableList.<V>of());
  }

  @MapFeature.Require({SUPPORTS_REMOVE, ALLOWS_NULL_KEY_QUERIES})
  public void testRemoveNullKeyAbsent() {
    assertFalse(multimap().remove(null, v0()));
    expectUnchanged();
  }

    public MetadataRetrievalException(String message) {
        this(message, null, null);
    }

    public MetadataRetrievalException(Throwable cause) {
        this(null, cause, null);
    }

    public MetadataRetrievalException(String message, Throwable cause) {
        this(message, cause, null);
    }

    public MetadataRetrievalException(String message, Throwable cause, ArtifactMetadata artifact) {

    initMultimapWithNullKey();
    assertContains(multimap().entries(), mapEntry((K) null, getValueForNullKey()));
  }

  @MapFeature.Require(ALLOWS_NULL_KEY_QUERIES)
  public void testContainsEntryWithNullKeyAbsent() {
    assertFalse(multimap().entries().contains(mapEntry(null, v0())));
  }

  @CollectionSize.Require(absent = ZERO)
  @MapFeature.Require(ALLOWS_NULL_VALUES)

        if (a.getVersion() != null) {
            result = 31 * result + a.getVersion().hashCode();
        }
        result = 31 * result + (a.getClassifier() != null ? a.getClassifier().hashCode() : 0);
        result = 31 * result + (a.getScope() != null ? a.getScope().hashCode() : 0);
        result = 31 * result
                + (a.getDependencyFilter() != null ? a.getDependencyFilter().hashCode() : 0);

    Comparator<? super E> result = comparator;
    if (result == null) {
      return comparator = Ordering.from(forwardMultiset().comparator()).<E>reverse();
    }
    return result;
  }

  @Nullable private transient SortedSet<E> elementSet;

  @Override
  public SortedSet<E> elementSet() {
    SortedSet<E> result = elementSet;
    if (result == null) {
      return elementSet = new SortedMultisets.ElementSet<E>(this);

    assertThrows(NullPointerException.class, () -> getMap().replace(k0(), null));
    expectUnchanged();
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_VALUE_QUERIES)
  public void testReplace_absentNullValueUnsupported() {
    try {
      getMap().replace(k3(), null);
    } catch (NullPointerException tolerated) {
      // permitted not to throw because it would be a no-op
    }

    assertSame(canonical, pool.intern(not));
  }

  public void testStrong_null() {
    Interner<String> pool = Interners.newStrongInterner();
    assertThrows(NullPointerException.class, () -> pool.intern(null));
  }

  public void testStrong_builder() {
    int concurrencyLevel = 42;
    Interner<Object> interner =
        Interners.newBuilder().strong().concurrencyLevel(concurrencyLevel).build();

  }
}

internal fun MediaType?.chooseCharset(): Pair<Charset, MediaType?> {
  var charset: Charset = Charsets.UTF_8
  var finalContentType: MediaType? = this
  if (this != null) {
    val resolvedCharset = this.charset()
    if (resolvedCharset == null) {
      charset = Charsets.UTF_8
      finalContentType = "$this; charset=utf-8".toMediaTypeOrNull()
    } else {
      charset = resolvedCharset
    }
  }

     * allowing the CAS below to succeed.
     */
    Thread currentThread = Thread.currentThread();
    if (!compareAndSet(null, currentThread)) {
      return; // someone else has run or is running.
    }

    boolean run = !isDone();
    T result = null;
    Throwable error = null;
    try {
      if (run) {
        result = runInterruptibly();