* uninterruptibly.
   *
   * @since 33.4.0 (but since 28.0 in the JRE flavor)
   */
  @J2ktIncompatible
  @GwtIncompatible // concurrency
  @IgnoreJRERequirement // Users will use this only if they're already using Duration.
  public static boolean awaitUninterruptibly(CountDownLatch latch, Duration timeout) {
    return awaitUninterruptibly(latch, toNanosSaturated(timeout), TimeUnit.NANOSECONDS);
  }

            // Mock send method
            public void send(final Object postcard) {
                // Mock implementation
            }
        };

        // Mock Postbox - no need to mock, the framework will handle it

        // Register components
        ComponentUtil.register(searchEngineClient, "searchEngineClient");
        ComponentUtil.register(systemHelper, "systemHelper");

   *
   * <ul>
   *   <li>If {@code count} is 0, {@code mean} may have any finite value (its only usage will be to
   *       get multiplied by 0 to calculate the sum), and the other parameters may have any values
   *       (they will not be used).
   *   <li>If {@code count} is 1, {@code sumOfSquaresOfDeltas} must be exactly 0.0 or {@link
   *       Double#NaN}.
   * </ul>
   */

 * continues. See {@link QueueWorker#workOnQueue} for details.
 *
 * <p>{@code RuntimeException}s thrown by tasks are simply logged and the executor keeps trucking.
 * If an {@code Error} is thrown, the error will propagate and execution will stop until it is
 * restarted by a call to {@link #execute}.
 */
@J2ktIncompatible
@GwtIncompatible
final class SequentialExecutor implements Executor {

   *
   * <p>If the graph is directed, the resultant edge will be directed; otherwise, it will be
   * undirected.
   *
   * <p>Values do not have to be unique. However, values must be non-null.
   *
   * <p>If {@code nodeU} and {@code nodeV} are not already present in this graph, this method will
   * silently {@link #addNode(Object) add} {@code nodeU} and {@code nodeV} to the graph.
   *

   *     no effect on the multimap.
   */
  @CanIgnoreReturnValue
  Collection<V> replaceValues(@ParametricNullness K key, Iterable<? extends V> values);

  /**
   * Removes all values associated with the key {@code key}.
   *
   * <p>Once this method returns, {@code key} will not be mapped to any values, so it will not

 * that every {@code Runnable} that is {@linkplain #add added} will be executed after {@link
 * #execute()} is called. Any {@code Runnable} added after the call to {@code execute} is still
 * guaranteed to execute. There is no guarantee, however, that listeners will be executed in the
 * order that they are added.
 *
 * <p>Exceptions thrown by a listener will be propagated up to the executor. Any exception thrown

     * Set runner thread before checking isDone(). If we were to check isDone() first, the task
     * might be cancelled before we set the runner thread. That would make it impossible to
     * interrupt, yet it will still run, since interruptTask will leave the runner value null,
     * allowing the CAS below to succeed.
     */
    Thread currentThread = Thread.currentThread();
    if (!compareAndSet(null, currentThread)) {

   * future to finish, and when it completes, run the listeners. This implementation will wait on
   * the source future indefinitely, so if the source future never completes, the adapter will never
   * complete either.
   *
   * <p>If the delegate future is interrupted or throws an unexpected unchecked exception, the
   * listeners will not be invoked.
   */

   * and column pair, they will be combined with the specified merging function in encounter order.
   *
   * <p>The returned {@code Collector} will throw a {@code NullPointerException} at collection time
   * if the row, column, value, or merging functions return null on any input.
   *
   * @since 33.2.0 (available since 21.0 in guava-jre)
   */
  @IgnoreJRERequirement // Users will use this only if they're already using streams.