* have been newly added to {@link ConcurrentMap}! These are marked with "Since: 1.8" in the
   * {@code ConcurrentMap} documentation. They will not function correctly and it is impossible for
   * Guava to fix them until Guava is ready to <i>require</i> Java 8 for all users.
   */
  ConcurrentMap<K, V> asMap();

  /**
   * Performs any pending maintenance operations needed by the cache. Exactly which activities are

with one finger for the rest of the day; and this was of very
little use, as it left no mark on the slate.

  `Herald, read the accusation!' said the King.

  On this the White Rabbit blew three blasts on the trumpet, and
then unrolled the parchment scroll, and read as follows:--

    `The Queen of Hearts, she made some tarts,
          All on a summer day:
      The Knave of Hearts, he stole those tarts,

 */
@Immutable
@ElementTypesAreNonnullByDefault
public interface HashFunction {
  /**
   * Begins a new hash code computation by returning an initialized, stateful {@code Hasher}
   * instance that is ready to receive data. Example:
   *
   * <pre>{@code
   * HashFunction hf = Hashing.md5();
   * HashCode hc = hf.newHasher()
   *     .putLong(id)
   *     .putBoolean(isActive)
   *     .hash();
   * }</pre>

    return result;
  }

  @Override
  public int size() {
    return size;
  }

  /**
   * Ensures that all of the internal structures in the HashBiMap are ready for this many elements.
   */
  private void ensureCapacity(int minCapacity) {
    if (nextInBucketKToV.length < minCapacity) {
      int oldCapacity = nextInBucketKToV.length;

  private State state = State.NOT_READY;

  /** Constructor for use by subclasses. */
  protected AbstractIterator() {}

  private enum State {
    /** We have computed the next element and haven't returned it yet. */
    READY,

    /** We haven't yet computed or have already returned the element. */
    NOT_READY,

    /** We have reached the end of the data and are finished. */

   * translates to "almost empty buffers", which can be filled immediately.
   *
   * On the other hand, past underutilization could mean that "the server responsible for handling
   * the request has become less ready for future requests", i.e. its caches become stale, and
   * requests become more likely to trigger expensive operations (a more extreme case of this

 *   <li>It doesn't offer a way to wait for multiple events before taking action. For example, it
 *       doesn't offer a way to wait for multiple producers to all report that they're "ready," nor
 *       does it offer a way to batch multiple events from a single producer together.
 *   <li>It doesn't support backpressure and other features needed for resilience.
 *   <li>It doesn't provide much control of threading.

with one finger for the rest of the day; and this was of very
little use, as it left no mark on the slate.

  `Herald, read the accusation!' said the King.

  On this the White Rabbit blew three blasts on the trumpet, and
then unrolled the parchment scroll, and read as follows:--

    `The Queen of Hearts, she made some tarts,
          All on a summer day:
      The Knave of Hearts, he stole those tarts,

    public T get() {
      // Another variant of Double Checked Locking.
      //
      // We use two volatile reads. We could reduce this to one by
      // putting our fields into a holder class, but (at least on x86)
      // the extra memory consumption and indirection are more
      // expensive than the extra volatile reads.
      long nanos = expirationNanos;
      long now = System.nanoTime();
      if (nanos == 0 || now - nanos >= 0) {

    MapMaker maker = new MapMaker();
    try {
      maker.initialCapacity(-1);
      fail();
    } catch (IllegalArgumentException expected) {
    }
  }

  // TODO(cpovirk): enable when ready (apparently after a change to our GWT emulation)
  public void xtestInitialCapacity_setTwice() {
    MapMaker maker = new MapMaker().initialCapacity(16);
    try {
      // even to the same value is not allowed