ms.add("b");
    ms.add(null);
    ms.add("a");
    ms.add("b");
    ms.add(null, 2);

    assertThat(ms).containsExactly(null, null, null, "a", "b", "b").inOrder();
    assertEquals(3, ms.count(null));

    SortedSet<@Nullable String> elementSet = ms.elementSet();
    assertEquals(null, elementSet.first());
    assertEquals("b", elementSet.last());

    assertThrows(NullPointerException.class, () -> future.addListener(null, directExecutor()));
  }

  public void testNullExecutor() {
    assertThrows(NullPointerException.class, () -> future.addListener(doNothing(), null));
  }

  public void testNullTimeUnit() throws Exception {
    future.set(1);
    assertThrows(NullPointerException.class, () -> future.get(0, null));
  }

    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) {

        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
    }
  }