private ExecutionSequencer() {}

  /** Creates a new instance. */
  public static ExecutionSequencer create() {
    return new ExecutionSequencer();
  }

  /** This reference acts as a pointer tracking the head of a linked list of ListenableFutures. */
  private final AtomicReference<ListenableFuture<@Nullable Void>> ref =
      new AtomicReference<>(immediateVoidFuture());

      // linked list starting from `newTable`. In general, each element from the old linked list
      // belongs to a different linked list from `newTable`. We insert each element in turn at the
      // head of its appropriate `newTable` linked list.
      while (oldNext != UNSET) {
        int entryIndex = oldNext - 1;
        int oldEntry = entries[entryIndex];

      if (count == 0 && !isLinkedHash) {
        contents = new ObjectCountLinkedHashMap<E>(contents);
        isLinkedHash = true;
        // to preserve insertion order through deletions, we have to switch to an actual linked
        // implementation at least for now, but this should be a super rare case
      } else if (buildInvoked) {
        contents = new ObjectCountHashMap<E>(contents);
        isLinkedHash = false;
      }

       * in that case, getProperty *will* return null.
       *
       * TODO(b/192002623): Handle that case: Either:
       *
       * - Skip non-string keys and values entirely, as proposed in the linked bug.
       *
       * - Throw ClassCastException instead of NullPointerException, as documented in the current
       *   Javadoc. (Note that we can't necessarily "just" change our call to `getProperty` to `get`

   * high 32 bits of each long is the "prev" pointer, whereas the low 32 bits is the "succ" pointer
   * (pointing to the next entry in the linked list). The pointers in [size(), entries.length) are
   * all "null" (UNSET).
   *
   * <p>A node with "prev" pointer equal to {@code ENDPOINT} is the first node in the linked list,
   * and a node with "next" pointer equal to {@code ENDPOINT} is the last node.
   */

 * implementations. Forked from {@link SetContainsBenchmark}.
 *
 * @author Nicholaus Shupe
 */
public class MapBenchmark {
  @Param({"Hash", "LinkedHM", "MapMaker1", "Immutable"})
  private Impl impl;

  public enum Impl {
    Hash {
      @Override
      Map<Element, Element> create(Collection<Element> keys) {
        Map<Element, Element> map = Maps.newHashMap();

      // linked list starting from `newTable`. In general, each element from the old linked list
      // belongs to a different linked list from `newTable`. We insert each element in turn at the
      // head of its appropriate `newTable` linked list.
      while (oldNext != UNSET) {
        int entryIndex = oldNext - 1;
        int oldEntry = entries[entryIndex];