@CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(absent = ZERO)
  public void testRemoveAll_allPresent() {
    assertTrue(
        "removeAll(intersectingCollection) should return true",
        collection.removeAll(MinimalCollection.of(e0())));
    expectMissing(e0());
  }

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(absent = ZERO)
  public void testRemoveAll_somePresent() {
    assertTrue(

    expectUnchanged();
  }

  @MapFeature.Require(absent = SUPPORTS_PUT)
  @CollectionSize.Require(absent = ZERO)
  public void testPutIfAbsent_unsupportedPresentDifferentValue() {
    try {
      getMap().putIfAbsent(k0(), v3());
    } catch (UnsupportedOperationException tolerated) {
    }
    expectUnchanged();
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_KEYS)

    assertEquals(2, multimap().size());
  }

  @CollectionSize.Require(absent = ZERO)
  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testPropagatesRemoveLastElementToMultimap() {
    Collection<V> result = multimap().asMap().get(k0());
    assertTrue(result.remove(v0()));
    assertGet(k0());
  }

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

  }

  @CollectionSize.Require(absent = ZERO)
  @CollectionFeature.Require(absent = NON_STANDARD_TOSTRING)
  @MapFeature.Require(ALLOWS_NULL_KEYS)
  public void testToStringWithNullKey() {
    initMultimapWithNullKey();
    testToStringMatchesAsMap();
  }

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

  @MapFeature.Require(ALLOWS_NULL_KEYS)
  @CollectionSize.Require(absent = ZERO)
  public void testGetOrDefault_nonNullWhenNullContained() {
    initMapWithNullKey();
    assertEquals(
        "getOrDefault(absent, default) should return default",
        v3(),
        getMap().getOrDefault(k3(), v3()));
  }

  @MapFeature.Require(ALLOWS_NULL_KEYS)
  @CollectionSize.Require(absent = ZERO)
  public void testGetOrDefault_presentNull() {

    }
  }

  @MapFeature.Require(absent = SUPPORTS_PUT)
  @CollectionSize.Require(absent = ZERO)
  public void testPutAll_unsupportedSomePresent() {
    try {
      putAll(MinimalCollection.of(e3(), e0()));
      fail("putAll(somePresent) should throw");
    } catch (UnsupportedOperationException expected) {
    }
    expectUnchanged();
  }

  @MapFeature.Require(absent = SUPPORTS_PUT)

  @MapFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(absent = ZERO)
  public void testRemoveKeyRemovesFromInverse() {
    getMap().remove(k0());
    expectMissing(e0());
  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(absent = ZERO)
  public void testRemoveKeyFromKeySetRemovesFromInverse() {
    getMap().keySet().remove(k0());

			continue
		case selectSend:
			j = nsends
			nsends++
		case selectRecv:
			nrecvs++
			j = len(cases) - nrecvs
		}

		sel[j] = scase{c: rc.ch, elem: rc.val}
		orig[j] = i
	}

	// Only a default case.
	if nsends+nrecvs == 0 {
		return dflt, false
	}

	// Compact sel and orig if necessary.
	if nsends+nrecvs < len(cases) {
		copy(sel[nsends:], sel[len(cases)-nrecvs:])

   * {@code Optional.empty}.
   */
  public static <T> Optional<T> absent() {
    return Absent.withType();
  }

  /**
   * Returns an {@code Optional} instance containing the given non-null reference. To have {@code
   * null} treated as {@link #absent}, use {@link #fromNullable} instead.
   *
   * <p><b>Comparison to {@code java.util.Optional}:</b> no differences.
   *

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_VALUES)
  @CollectionSize.Require(absent = ZERO)
  public void testReplace_presentNullValueUnsupported() {
    try {
      getMap().replace(k0(), null);
      fail("Expected NullPointerException");
    } catch (NullPointerException expected) {
    }
    expectUnchanged();
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_VALUE_QUERIES)