if (!hasNext()) {
          throw new NoSuchElementException();
        }
        /*
         * requireNonNull is safe because our callers always pass non-null arguments. Each element
         * of the array becomes null only when we iterate past it and then clear it.
         */
        I result = requireNonNull(elements[index]);
        elements[index] = null;
        index++;
        return result;
      }
    };

  //
  // * Be responsive to interruption
  // * Don't create Waiter nodes if you aren't going to park, this helps reduce contention on the
  //   waiters field.
  // * Future completion is defined by when #value becomes non-null/non SetFuture
  // * Future completion can be observed if the waiters field contains a TOMBSTONE

  // Timed Get
  // There are a few design constraints to consider

    // such that none of the subsequent iterations observed it, despite the fact that at every point
    // in time it was present somewhere int the map. This becomes increasingly unlikely as
    // CONTAINS_VALUE_RETRIES increases, though without locking it is theoretically possible.
    final Segment<K, V, E, S>[] segments = this.segments;
    long last = -1L;

    int pos = indexIn(string);
    if (pos == -1) {
      return string;
    }

    char[] chars = string.toCharArray();
    int spread = 1;

    // This unusual loop comes from extensive benchmarking
    OUT:
    while (true) {
      pos++;
      while (true) {
        if (pos == chars.length) {
          break OUT;
        }
        if (matches(chars[pos])) {

        if (!hasNext()) {
          throw new NoSuchElementException();
        }
        /*
         * requireNonNull is safe because our callers always pass non-null arguments. Each element
         * of the array becomes null only when we iterate past it and then clear it.
         */
        I result = requireNonNull(elements[index]);
        elements[index] = null;
        index++;
        return result;
      }
    };

    int pos = indexIn(string);
    if (pos == -1) {
      return string;
    }

    char[] chars = string.toCharArray();
    int spread = 1;

    // This unusual loop comes from extensive benchmarking
    OUT:
    while (true) {
      pos++;
      while (true) {
        if (pos == chars.length) {
          break OUT;
        }
        if (matches(chars[pos])) {

  // safely publish these objects and we won't need this whole discussion.
  // TODO(user,lukes): consider adding volatile to all these fields since in current known JVMs
  // that should resolve the issue. This comes at the cost of adding more write barriers to the
  // implementations.

  private Futures() {}

  /**
   * Creates a {@code ListenableFuture} which has its value set immediately upon construction. The