cachingHashMap.remove(key);
      return null;
    }
  }

  @CanIgnoreReturnValue
  @Override
  public V put(K key, V value) {
    checkNotNull(key);
    checkNotNull(value);
    Timestamped<V> oldValue = cachingHashMap.put(key, new Timestamped<V>(value, ticker));
    if (oldValue == null) {
      return null;
    }

  @CollectionSize.Require(absent = ZERO)
  public void testCompute_presentNullToNull() {
    // The spec is somewhat ambiguous about this case, but the actual default implementation
    // in Map will remove a present null.
    initMapWithNullValue();
    assertNull(
        "Map.compute(presentMappedToNull, functionReturningNull) should return null",
        getMap()

                }));
    expectReplacement(entry(getKeyForNullValue(), v3()));
  }

  @MapFeature.Require({SUPPORTS_PUT, ALLOWS_NULL_KEYS})
  public void testMergeAbsentNullKey() {
    assertEquals(
        "Map.merge(null, value, function) should return value",
        v3(),
        getMap()
            .merge(
                null,
                v3(),

    final String result =
        MoreObjects.toStringHelper(new TestClass())
            .addValue(null)
            .addValue("Hello")
            .addValue(null)
            .toString();
    final String expected = "TestClass{null, Hello, null}";

    assertEquals(expected, result);
  }

  public void testToStringLenient_addValueWithNullValue() {
    final String result =

                })
            .named("unmodifiableBiMap[HashBiMap]")
            .withFeatures(
                CollectionSize.ANY,
                MapFeature.ALLOWS_NULL_VALUES,
                MapFeature.ALLOWS_NULL_KEYS,
                MapFeature.ALLOWS_ANY_NULL_QUERIES,
                MapFeature.REJECTS_DUPLICATES_AT_CREATION,
                CollectionFeature.SERIALIZABLE)
            .createTestSuite());
    suite.addTest(

  }

  @MapFeature.Require(ALLOWS_NULL_VALUES)
  @CollectionSize.Require(absent = ZERO)
  public void testContainsNullValueYes() {
    initMultimapWithNullValue();
    assertTrue(multimap().containsValue(null));
  }

  @MapFeature.Require(ALLOWS_NULL_VALUE_QUERIES)
  public void testContainsNullValueNo() {
    assertFalse(multimap().containsValue(null));
  }

      equalsTester.addEqualityGroup(reference, equalObject1, null);
      fail("Should fail on null equal object");
    } catch (NullPointerException e) {
    }
  }

  /** Test adding null equal object yields error */
  public void testAddNullEqualObject() {
    try {
      equalsTester.addEqualityGroup(reference, (Object[]) null);
      fail("Should fail on null equal object");
    } catch (NullPointerException e) {
    }
  }

  /**

   * find it when available. When this is null, use the slow way.
   */
  @J2ktIncompatible
  @GwtIncompatible // java.lang.reflect
  @CheckForNull
  private static final Method getStackTraceElementMethod = (jla == null) ? null : getGetMethod();

  /**
   * The "getStackTraceDepth" method, only available on some JDKs so we use reflection to find it
   * when available. When this is null, use the slow way.
   */

   * find it when available. When this is null, use the slow way.
   */
  @J2ktIncompatible
  @GwtIncompatible // java.lang.reflect
  @CheckForNull
  private static final Method getStackTraceElementMethod = (jla == null) ? null : getGetMethod();

  /**
   * The "getStackTraceDepth" method, only available on some JDKs so we use reflection to find it
   * when available. When this is null, use the slow way.
   */

   *     null} is treated as the four-character string {@code "null"}.
   * @param args the arguments to be substituted into the message template. The first argument
   *     specified is substituted for the first occurrence of {@code "%s"} in the template, and so
   *     forth. A {@code null} argument is converted to the four-character string {@code "null"};