/**
   * Adds the given value.
   *
   * @param x the value to add
   */
  @Override
  public void add(long x) {
    Cell[] as;
    long b, v;
    int[] hc;
    Cell a;
    int n;
    if ((as = cells) != null || !casBase(b = base, b + x)) {
      boolean uncontended = true;
      if ((hc = threadHashCode.get()) == null
          || as == null
          || (n = as.length) < 1
          || (a = as[(n - 1) & hc[0]]) == null

public final class Tables {
  private Tables() {}

  /**
   * Returns a {@link Collector} that accumulates elements into a {@code Table} created using the
   * specified supplier, whose cells are generated by applying the provided mapping functions to the
   * input elements. Cells are inserted into the generated {@code Table} in encounter order.
   *
   * <p>If multiple input elements map to the same row and column, an {@code IllegalStateException}

    // tells the computing thread when to start computing
    CountDownLatch computeSignal = new CountDownLatch(1);
    // tells the main thread when computation is pending
    CountDownLatch secondSignal = new CountDownLatch(1);
    // tells the main thread when the second get has started
    CountDownLatch thirdSignal = new CountDownLatch(1);
    // tells the main thread when the third get has started

 *   }
 * }
 *
 * public void testMySubtypes() throws Exception {
 *   new MySubtypeTests().testAllDeclarations();
 * }
 * }
 *
 * The calls to {@link #isSubtype} and {@link #notSubtype} tells the framework what assertions need
 * to be made.
 *
 * <p>The declaration methods must be public.
 */
@AndroidIncompatible // only used by android incompatible tests.
@NullUnmarked

   * update the underlying table, and vice versa. The cell set does not support the {@code add} or
   * {@code addAll} methods.
   *
   * @return set of table cells consisting of row key / column key / value triplets
   */
  Set<Cell<R, C, V>> cellSet();

  /**
   * Returns a set of row keys that have one or more values in the table. Changes to the set will

   *
   * <p>The returned set's iterator traverses the mappings with the first row key, the mappings with
   * the second row key, and so on.
   *
   * <p>The value in the returned cells may change if the table subsequently changes.
   *
   * @return set of table cells consisting of row key / column key / value triplets
   */
  @Override
  public Set<Cell<R, C, @Nullable V>> cellSet() {
    return super.cellSet();
  }

  @Override