* fixed but arbitrary point in time. Note that most users should use {@link Stopwatch} instead of
 * interacting with this class directly.
 *
 * <p><b>Warning:</b> this interface can only be used to measure elapsed time, not wall time.
 *
 * @author Kevin Bourrillion
 * @since 10.0 (<a href="https://github.com/google/guava/wiki/Compatibility">mostly
 *     source-compatible</a> since 9.0)
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault

 *
 * <p>In contrast, <i>wall time</i> is a reading of "now" as given by a method like
 * {@link System#currentTimeMillis()}, best represented as an {@link java.time.Instant}. Such values
 * <i>can</i> be subtracted to obtain a {@code Duration} (such as by {@code Duration.between}), but
 * doing so does <i>not</i> give a reliable measurement of elapsed time, because wall time readings

 * fixed but arbitrary point in time. Note that most users should use {@link Stopwatch} instead of
 * interacting with this class directly.
 *
 * <p><b>Warning:</b> this interface can only be used to measure elapsed time, not wall time.
 *
 * @author Kevin Bourrillion
 * @since 10.0 (<a href="https://github.com/google/guava/wiki/Compatibility">mostly
 *     source-compatible</a> since 9.0)
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault

 *
 * <p>In contrast, <i>wall time</i> is a reading of "now" as given by a method like
 * {@link System#currentTimeMillis()}, best represented as an {@link java.time.Instant}. Such values
 * <i>can</i> be subtracted to obtain a {@code Duration} (such as by {@code Duration.between}), but
 * doing so does <i>not</i> give a reliable measurement of elapsed time, because wall time readings

 *   <li>enqueuing weak references to unreachable referents in their reference queue
 * </ul>
 *
 * <p>This class uses (possibly repeated) invocations of {@link java.lang.System#gc()} to cause
 * finalization to happen. However, a call to {@code System.gc()} is specified to be no more than a
 * hint, so this technique may fail at the whim of the JDK implementation, for example if a user

 *   <li>enqueuing weak references to unreachable referents in their reference queue
 * </ul>
 *
 * <p>This class uses (possibly repeated) invocations of {@link java.lang.System#gc()} to cause
 * finalization to happen. However, a call to {@code System.gc()} is specified to be no more than a
 * hint, so this technique may fail at the whim of the JDK implementation, for example if a user

        if (atomic.compareAndSet(oldValue, newValue)) {
          return oldValue;
        }
        // value changed
      }
    }
  }

  /**
   * Copies all of the mappings from the specified map to this map. The effect of this call is
   * equivalent to that of calling {@code put(k, v)} on this map once for each mapping from key
   * {@code k} to value {@code v} in the specified map. The behavior of this operation is undefined

      for (PerListenerQueue<L> queue : listeners) {
        queue.add(event, label);
      }
    }
  }

  /**
   * Dispatches all events enqueued prior to this call, serially and in order, for every listener.
   *
   * <p>Note: this method is idempotent and safe to call from any thread
   */
  public void dispatch() {
    // iterate by index to avoid concurrent modification exceptions

   *       </ul>
   *   <li>another java.util.Map delegate implementation. In most modern JDKs, normal java.util hash
   *       collections intelligently fall back to a binary search tree if hash table collisions are
   *       detected. Rather than going to all the trouble of reimplementing this ourselves, we
   *       simply switch over to use the JDK implementation wholesale if probable hash flooding is

   * skipped element by immediately calling {@code remove()} on the returned fluent iterable's
   * iterator, as the {@code Iterator} contract states that a call to {@code * remove()} before a
   * call to {@code next()} will throw an {@link IllegalStateException}.
   *
   * <p><b>{@code Stream} equivalent:</b> {@link Stream#skip} (same).
   */
  public final FluentIterable<E> skip(int numberToSkip) {