* return hex.decode("deadbeef"); // throws an IllegalArgumentException
 * }</pre>
 *
 * <p>It is guaranteed that {@code encoding.decode(encoding.encode(x))} is always equal to {@code
 * x}, but the reverse does not necessarily hold.
 *
 * <table>
 * <caption>Encodings</caption>
 * <tr>
 * <th>Encoding
 * <th>Alphabet
 * <th>{@code char:byte} ratio
 * <th>Default padding
 * <th>Comments
 * <tr>
 * <td>{@link #base16()}

    future2 = null;

    /*
     * Futures should be collected even if combiner never runs. This is kind of a silly test, since
     * the combiner is almost certain to hold its own reference to the futures, and a real app would
     * hold a reference to the executor and thus to the combiner. What we really care about is that
     * the futures are released once the combiner is done running. But we happen to provide this

    stopwatch.sleepMillis(4000); // #3: becomes cold again
    for (int i = 0; i < 8; i++) {
      limiter.acquire(); // // #4
    }
    stopwatch.sleepMillis(500); // #5: to repay for the last acquire
    stopwatch.sleepMillis(2000); // #6: didn't get cold! It would take another 2 seconds to go cold
    for (int i = 0; i < 8; i++) {
      limiter.acquire(); // #7
    }
    assertEvents(

    }

    @Override
    public boolean isEmpty() {
      assertTrue(Thread.holdsLock(mutex));
      return super.isEmpty();
    }

    /* Don't test iterator(); it may or may not hold the mutex. */

    @Override
    public boolean remove(@Nullable Object o) {
      assertTrue(Thread.holdsLock(mutex));
      return super.remove(o);
    }

    @Override

  public static <K extends @Nullable Object, V extends @Nullable Object>
      HashMultimap<K, V> create() {
    return new HashMultimap<>();
  }

  /**
   * Constructs an empty {@code HashMultimap} with enough capacity to hold the specified numbers of
   * keys and values without rehashing.
   *
   * <p>This method will soon be deprecated in favor of {@code
   * MultimapBuilder.hashKeys(expectedKeys).hashSetValues(expectedValuesPerKey).build()}.

     * implementation, because {@code map.get()} returns a view collection that changes in the
     * course of a call to {@code remove()}. Thus, the expectation doesn't hold that {@code
     * map.remove(x)} returns the same value which {@code map.get(x)} did immediately beforehand.
     */
    @Override
    public void testRemove() {
      final Map<String, Map<Integer, Character>> map;

  /**
   * Creates a {@code CompactHashSet} instance, with a high enough "initial capacity" that it
   * <i>should</i> hold {@code expectedSize} elements without growth.
   *
   * @param expectedSize the number of elements you expect to add to the returned set
   * @return a new, empty {@code CompactHashSet} with enough capacity to hold {@code expectedSize}
   *     elements without resizing

   * propagate cancellation) and {@link #toString()}. To access the futures' <i>values</i>, {@code
   * AggregateFuture} attaches listeners that hold references to one or more inputs. And in the case
   * of {@link CombinedFuture}, the user-supplied callback usually has its own references to inputs.
   */
  /*

    HashSet<E> set = newHashSet();
    Iterators.addAll(set, elements);
    return set;
  }

  /**
   * Returns a new hash set using the smallest initial table size that can hold {@code expectedSize}
   * elements without resizing. Note that this is not what {@link HashSet#HashSet(int)} does, but it
   * is what most users want and expect it to do.
   *

  }

  /**
   * Returns the empty multimap.
   *
   * <p><b>Performance note:</b> the instance returned is a singleton.
   */
  // Casting is safe because the multimap will never hold any elements.
  @SuppressWarnings("unchecked")
  public static <K, V> ImmutableListMultimap<K, V> of() {
    return (ImmutableListMultimap<K, V>) EmptyImmutableListMultimap.INSTANCE;
  }