checkArgument(xValues.size() == yValues.size());
    PairedStatsAccumulator accumulator = new PairedStatsAccumulator();
    for (int index = 0; index < xValues.size(); index++) {
      accumulator.add(xValues.get(index), yValues.get(index));
    }
    return accumulator;
  }

  /**
   * Creates a {@link PairedStatsAccumulator} filled with the given lists of {@code x} and {@code y}

    checkArgument(values.length > 0);
    double mean = values[0];
    for (int index = 1; index < values.length; index++) {
      double value = values[index];
      if (isFinite(value) && isFinite(mean)) {
        // Art of Computer Programming vol. 2, Knuth, 4.2.2, (15)
        mean += (value - mean) / (index + 1);
      } else {
        mean = calculateNewMeanNonFinite(mean, value);
      }
    }

  // The fake cast to E is safe because the creation methods only allow E's
  @Override
  @SuppressWarnings("unchecked")
  public E get(int index) {
    checkElementIndex(index, size);
    // requireNonNull is safe because we guarantee that the first `size` elements are non-null.
    return (E) requireNonNull(array[index]);
  }

  // TODO(lowasser): benchmark optimizations for equals() and see if they're worthwhile

      action.accept(keyList.get(i), valueList.get(i));
    }
  }

  @Override
  @CheckForNull
  public V get(@CheckForNull Object key) {
    int index = keySet.indexOf(key);
    return (index == -1) ? null : valueList.get(index);
  }

  @Override
  boolean isPartialView() {
    return keySet.isPartialView() || valueList.isPartialView();
  }

    for (int i = 0; i < equalityGroup.length; i++) {
      Object element = equalityGroup[i];
      if (element == null) {
        throw new NullPointerException("at index " + i);
      }
      list.add(element);
    }
    equalityGroups.add(list);
    return this;
  }

  /** Run tests on equals method, throwing a failure on an invalid test */
  @CanIgnoreReturnValue

  JdkBackedImmutableSet(Set<?> delegate, ImmutableList<E> delegateList) {
    this.delegate = delegate;
    this.delegateList = delegateList;
  }

  @Override
  E get(int index) {
    return delegateList.get(index);
  }

  @Override
  public boolean contains(@CheckForNull Object object) {
    return delegate.contains(object);
  }

  @Override
  boolean isPartialView() {
    return false;
  }

    @ParametricNullness
    public V get(int index) {
      refreshIfEmpty();
      return getListDelegate().get(index);
    }

    @Override
    @ParametricNullness
    public V set(int index, @ParametricNullness V element) {
      refreshIfEmpty();
      return getListDelegate().set(index, element);
    }

    @Override
    public void add(int index, @ParametricNullness V element) {
      refreshIfEmpty();

      values.add(null);
    }

    this.values = values;
  }

  @Override
  final void collectOneValue(int index, @ParametricNullness V returnValue) {
    List<@Nullable Present<V>> localValues = values;
    if (localValues != null) {
      localValues.set(index, new Present<>(returnValue));
    }
  }

  @Override
  final void handleAllCompleted() {
    List<@Nullable Present<V>> localValues = values;

    }
    int mask = hashTableMask();
    int index =
        CompactHashing.remove(
            object,
            /* value= */ null,
            mask,
            requireTable(),
            requireEntries(),
            requireElements(),
            /* values= */ null);
    if (index == -1) {
      return false;
    }

    moveLastEntry(index, mask);
    size--;
    incrementModCount();

  }

  @Override
  public ImmutableSortedSet<E> elementSet() {
    return forward.elementSet().descendingSet();
  }

  @Override
  Entry<E> getEntry(int index) {
    return forward.entrySet().asList().reverse().get(index);
  }

  @Override
  public ImmutableSortedMultiset<E> descendingMultiset() {
    return forward;
  }

  @Override