@MapFeature.Require(SUPPORTS_PUT)
  public void testComputeIfPresent_supportedAbsent() {
    assertNull(
        "computeIfPresent(notPresent, function) should return null",
        getMap()
            .computeIfPresent(
                k3(),
                (k, v) -> {
                  throw new AssertionFailedError();
                }));
    expectUnchanged();
  }

      }
    }

    @Override
    @CheckForNull
    public V computeIfPresent(
        K key, BiFunction<? super K, ? super @NonNull V, ? extends @Nullable V> remappingFunction) {
      synchronized (mutex) {
        return delegate().computeIfPresent(key, remappingFunction);
      }
    }

    @Override
    @CheckForNull
    public V compute(

   * @deprecated Unsupported operation.
   */
  @Deprecated
  @Override
  @DoNotCall("Always throws UnsupportedOperationException")
  @CheckForNull
  public final V computeIfPresent(
      K key, BiFunction<? super K, ? super V, ? extends @Nullable V> remappingFunction) {
    throw new UnsupportedOperationException();
  }

  /**

        K key, java.util.function.Function<? super K, ? extends V> mappingFunction) {
      throw new UnsupportedOperationException();
    }

    @Override
    @CheckForNull
    public V computeIfPresent(
        K key, BiFunction<? super K, ? super @NonNull V, ? extends @Nullable V> remappingFunction) {
      throw new UnsupportedOperationException();
    }

    @Override
    @CheckForNull

    checkNotNull(key);
    checkNotNull(function);
    return compute(key, (k, oldValue) -> (oldValue == null) ? function.apply(key) : oldValue);
  }

  @Override
  @CheckForNull
  public V computeIfPresent(
      K key, BiFunction<? super K, ? super V, ? extends @Nullable V> function) {
    checkNotNull(key);
    checkNotNull(function);