*/
  public static HashFunction concatenating(
      HashFunction first, HashFunction second, HashFunction... rest) {
    // We can't use Lists.asList() here because there's no hash->collect dependency
    List<HashFunction> list = new ArrayList<>();
    list.add(first);
    list.add(second);
    Collections.addAll(list, rest);
    return new ConcatenatedHashFunction(list.toArray(new HashFunction[0]));
  }

  /**

   * implement shutdown and termination behavior.
   *
   * <p>The implementation deviates from the {@code ExecutorService} specification with regards to
   * the {@code shutdownNow} method. First, "best-effort" with regards to canceling running tasks is
   * implemented as "no-effort". No interrupts or other attempts are made to stop threads executing

      first = false;
      if (o == collection) {
        sb.append("(this Collection)");
      } else {
        sb.append(o);
      }
    }
    return sb.append(']').toString();
  }

  /** Returns best-effort-sized StringBuilder based on the given collection size. */
  static StringBuilder newStringBuilderForCollection(int size) {
    checkNonnegative(size, "size");

      first = false;
      if (o == collection) {
        sb.append("(this Collection)");
      } else {
        sb.append(o);
      }
    }
    return sb.append(']').toString();
  }

  /** Returns best-effort-sized StringBuilder based on the given collection size. */
  static StringBuilder newStringBuilderForCollection(int size) {
    checkNonnegative(size, "size");

   * precise conditions for skipping the copy operation are undefined.
   *
   * @throws NullPointerException if any of {@code elements} is null
   * @since 7.0 (source-compatible since 2.0)
   */
  // This the best we could do to get copyOfEnumSet to compile in the mainline.
  // The suppression also covers the cast to E[], discussed below.
  // In the backport, we don't have those cases and thus don't need this suppression.

    keyEquivalence = builder.getKeyEquivalence();
    this.entryHelper = entryHelper;

    int initialCapacity = Math.min(builder.getInitialCapacity(), MAXIMUM_CAPACITY);

    // Find power-of-two sizes best matching arguments. Constraints:
    // (segmentCount > concurrencyLevel)
    int segmentShift = 0;
    int segmentCount = 1;
    while (segmentCount < concurrencyLevel) {
      ++segmentShift;

    }
    // The future has already been set to something. If it is cancellation we should cancel the
    // incoming future.
    if (localValue instanceof Cancellation) {
      // we don't care if it fails, this is best-effort.
      future.cancel(((Cancellation) localValue).wasInterrupted);
    }
    return false;
  }

  /**
   * Returns a value that satisfies the contract of the {@link #value} field based on the state of

 *       (in a way that affects its {@link Object#equals} behavior) while it is contained in a
 *       collection. Undefined behavior and bugs will result. It's generally best to avoid using
 *       mutable objects as elements at all, as many users may expect your "immutable" object to be
 *       <i>deeply</i> immutable.
 * </ul>
 *
 * <h4>Performance notes</h4>
 *
 * <ul>

 *       (in a way that affects its {@link Object#equals} behavior) while it is contained in a
 *       collection. Undefined behavior and bugs will result. It's generally best to avoid using
 *       mutable objects as elements at all, as many users may expect your "immutable" object to be
 *       <i>deeply</i> immutable.
 * </ul>
 *
 * <h4>Performance notes</h4>
 *
 * <ul>

   * precise conditions for skipping the copy operation are undefined.
   *
   * @throws NullPointerException if any of {@code elements} is null
   * @since 7.0 (source-compatible since 2.0)
   */
  // This the best we could do to get copyOfEnumSet to compile in the mainline.
  // The suppression also covers the cast to E[], discussed below.
  // In the backport, we don't have those cases and thus don't need this suppression.