* method provides an atomic compare-and-update of some key's value.
     *
     * @param key the key under which to store the session data, must not be {@code null}
     * @param oldValue the expected data currently associated with the key, may be {@code null}
     * @param newValue the data to associate with the key, may be {@code null} to remove the mapping

    int entryForKey = findEntryByKey(key, keyHash);
    if (entryForKey != ABSENT) {
      V oldValue = values[entryForKey];
      if (Objects.equals(oldValue, value)) {
        return value;
      } else {
        replaceValueInEntry(entryForKey, value, force);
        return oldValue;
      }
    }

    int valueHash = Hashing.smearedHash(value);

  }

  public void testPutAndGetInstance() {
    assertThat(map.putInstance(Integer.class, new Integer(5))).isNull();

    Integer oldValue = map.putInstance(Integer.class, new Integer(7));
    assertEquals(5, (int) oldValue);

    Integer newValue = map.getInstance(Integer.class);
    assertEquals(7, (int) newValue);

    // Won't compile: map.putInstance(Double.class, new Long(42));
  }

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

  @Override
  public @Nullable V computeIfPresent(
      K key, BiFunction<? super K, ? super V, ? extends @Nullable V> function) {
    checkNotNull(key);
    checkNotNull(function);
    return compute(key, (k, oldValue) -> (oldValue == null) ? null : function.apply(k, oldValue));
  }

  @Override

      cellRowIndices[i] = requireNonNull(rowIndex.get(rowKey));
      Map<C, V> thisRow = requireNonNull(rows.get(rowKey));
      cellColumnInRowIndices[i] = thisRow.size();
      V oldValue = thisRow.put(columnKey, value);
      checkNoDuplicate(rowKey, columnKey, oldValue, value);
      requireNonNull(columns.get(columnKey)).put(rowKey, value);
    }
    this.cellRowIndices = cellRowIndices;
    this.cellColumnInRowIndices = cellColumnInRowIndices;

      countLoad.incrementAndGet();
      return key;
    }

    @GwtIncompatible // reload
    @Override
    public ListenableFuture<Integer> reload(Integer key, Integer oldValue) {
      countReload.incrementAndGet();
      return immediateFuture(oldValue + 1);
    }

    public int getLoadCount() {
      return countLoad.get();
    }

    public int getReloadCount() {
      return countReload.get();
    }

      cellRowIndices[i] = requireNonNull(rowIndex.get(rowKey));
      Map<C, V> thisRow = requireNonNull(rows.get(rowKey));
      cellColumnInRowIndices[i] = thisRow.size();
      V oldValue = thisRow.put(columnKey, value);
      checkNoDuplicate(rowKey, columnKey, oldValue, value);
      requireNonNull(columns.get(columnKey)).put(rowKey, value);
    }
    this.cellRowIndices = cellRowIndices;
    this.cellColumnInRowIndices = cellColumnInRowIndices;

  public @Nullable V remove(@Nullable Object key) {
    Map<K, V> delegate = delegateOrNull();
    if (delegate != null) {
      return delegate.remove(key);
    }
    Object oldValue = removeHelper(key);
    return (oldValue == NOT_FOUND) ? null : (V) oldValue;
  }

  private @Nullable Object removeHelper(@Nullable Object key) {
    if (needsAllocArrays()) {
      return NOT_FOUND;
    }
    int mask = hashTableMask();

    }
    for (int i = 0; i < N; i++) {
      assertEquals(2 * i, (int) inverse.get(2 * i + 1));
    }
    for (int i = 0; i < N; i++) {
      int oldValue = bimap.get(2 * i);
      assertEquals(2 * i + 1, (int) bimap.put(2 * i, oldValue - 2));
    }
    for (int i = 0; i < N; i++) {
      assertEquals(2 * i - 1, (int) bimap.get(2 * i));
    }
    for (int i = 0; i < N; i++) {

    for (double y : OTHER_MANY_VALUES) {
      accumulator.add(ONE_VALUE, y);
    }
    return accumulator.snapshot();
  }

  private static PairedStats buildConstantValuesPairedStats() {
    PairedStatsAccumulator accumulator = new PairedStatsAccumulator();
    for (int i = 0; i < MANY_VALUES_COUNT; ++i) {
      accumulator.add(ONE_VALUE, OTHER_ONE_VALUE);
    }
    return accumulator.snapshot();
  }