* cannot be found (it is only to be found in fairly recent JDKs). Tries to test method {@link
   * sun.misc.JavaLangAccess#getStackTraceDepth(Throwable) getStackTraceDepth} prior to return it
   * (might fail some JDKs).
   *
   * <p>See <a href="https://github.com/google/guava/issues/2887">Throwables#lazyStackTrace throws
   * UnsupportedOperationException</a>.
   */
  @J2ktIncompatible

         * work with all JDK versions, TypeResolver must return the appropriate TypeVariable
         * implementation in each of the three possible cases:
         *
         * 1. Prior to JDK 7u51, the JDK TypeVariable implementation interoperates with ours.
         * Therefore, we can always create our own TypeVariable.
         *

child was very fond of pretending to be two people.  `But it's no
use now,' thought poor Alice, `to pretend to be two people!  Why,
there's hardly enough of me left to make ONE respectable
person!'

  Soon her eye fell on a little glass box that was lying under
the table:  she opened it, and found in it a very small cake, on
which the words `EAT ME' were beautifully marked in currants.

 *
 * <pre>{@code
 * public enum PersonFunnel implements Funnel<Person> {
 *   INSTANCE;
 *   public void funnel(Person person, PrimitiveSink into) {
 *     into.putUnencodedChars(person.getFirstName())
 *         .putUnencodedChars(person.getLastName())
 *         .putInt(person.getAge());
 *   }
 * }
 * }</pre>
 *
 * @author Dimitris Andreou
 * @since 11.0
 */
@Beta

    for prod and one for tests. However, unlike our other packages, as of this
    writing it has test supersource but no prod supersource.

    GWT happens to use the prod .gwt.xml, so it looks for no supersource for
    tests, either. This causes it to fail to find AtomicLongMapTest.

    Our workaround is to tell GWT that util.concurrent and all other packages

 * doing so does <i>not</i> give a reliable measurement of elapsed time, because wall time readings
 * are inherently approximate, routinely affected by periodic clock corrections. Because this class
 * (by default) uses {@link System#nanoTime}, it is unaffected by these changes.
 *
 * <p>Use this class instead of direct calls to {@link System#nanoTime} for two reasons:
 *
 * <ul>

       * to test it.
       */
      return;
    }

    /*
     * Only under Windows (or hypothetically when running with some other non-POSIX, ACL-based
     * filesystem) does our prod code look up the username. Thus, this test doesn't necessarily test
     * anything interesting under most environments. Still, we can run it (except for Android, at

   * listeners, see {@link Futures}. For a simplified but general listener interface, see {@link
   * Futures#addCallback addCallback()}.
   *
   * <p>Memory consistency effects: Actions in a thread prior to adding a listener <a
   * href="https://docs.oracle.com/javase/specs/jls/se7/html/jls-17.html#jls-17.4.5">
   * <i>happen-before</i></a> its execution begins, perhaps in another thread.
   *

   * list must be sorted into ascending order according to the specified comparator (as by the
   * {@link Collections#sort(List, Comparator) Collections.sort(List, Comparator)} method), prior to
   * making this call. If it is not sorted, the results are undefined.
   *
   * <p>If there are elements in the list which compare as equal to the key, the choice of {@link

    executor.execute(task);
    assertEquals(1, numCalls.get());
  }

  /*
   * Under Android, MyError propagates up and fails the test?
   *
   * TODO(b/218700094): Does this matter to prod users, or is it just a feature of our testing
   * environment? If the latter, maybe write a custom Executor that avoids failing the test when it
   * sees an Error?
   */
  @AndroidIncompatible