}

  /**
   * {@link AtomicHelper} based on {@link sun.misc.Unsafe}.
   *
   * <p>Static initialization of this class will fail if the {@link sun.misc.Unsafe} object cannot
   * be accessed.
   */
  @SuppressWarnings({"sunapi", "removal"}) // b/318391980
  private static final class UnsafeAtomicHelper extends AtomicHelper {
    static final sun.misc.Unsafe UNSAFE;

   * higher than performing just the operation without enforcing the capacity constraint.
   *
   * This implementation uses a per-segment queue to record a memento of the additions, removals,
   * and accesses that were performed on the map. The queue is drained on writes and when it exceeds
   * its capacity threshold.
   *
   * The Least Recently Used page replacement algorithm was chosen due to its simplicity, high hit

   * addAll} method is implemented as a sequence of {@code put} invocations on the backing map.
   *
   * <p>The specified map must be empty at the time this method is invoked, and should not be
   * accessed directly after this method returns. These conditions are ensured if the map is created
   * empty, passed directly to this method, and no reference to the map is retained, as illustrated
   * in the following code fragment:
   *

 *
 * <p>If {@link #expireAfterWrite expireAfterWrite} or {@link #expireAfterAccess expireAfterAccess}
 * is requested entries may be evicted on each cache modification, on occasional cache accesses, or
 * on calls to {@link Cache#cleanUp}. Expired entries may be counted by {@link Cache#size}, but will
 * never be visible to read or write operations.
 *

      for (int i = delegateIndex; i < delegates.size(); i++) {
        if (delegates.get(i).setFuture(inputFuture)) {
          recordCompletion();
          // this is technically unnecessary, but should speed up later accesses
          delegateIndex = i + 1;
          return;
        }
      }
      // If all the delegates were complete, no reason for the next listener to have to