* elements. The generated map is sorted by the specified comparator.
   *
   * <p>If the mapped keys contain duplicates (according to the specified comparator), an {@code
   * IllegalArgumentException} is thrown when the collection operation is performed. (This differs
   * from the {@code Collector} returned by {@link Collectors#toMap(Function, Function)}, which
   * throws an {@code IllegalStateException}.)
   */

    // tells the computing thread when to start computing
    final CountDownLatch computeSignal = new CountDownLatch(1);
    // tells the main thread when computation is pending
    final CountDownLatch secondSignal = new CountDownLatch(1);
    // tells the main thread when the second get has started
    final CountDownLatch thirdSignal = new CountDownLatch(1);
    // tells the main thread when the third get has started

    Iterator<String> itr2 = Iterators.concat(itr1, Iterators.singletonIterator("d"));
    assertEquals("c", itr2.next());
    assertEquals("d", itr2.next());
  }

  /** Illustrates the somewhat bizarre behavior when a null is passed in. */
  public void testConcatContainingNull() {
    Iterator<Iterator<Integer>> input =
        (Iterator<Iterator<Integer>>)

   *
   * <p>If the supplied future is {@linkplain #isDone done} when this method is called and the call
   * is accepted, then this future is guaranteed to have been completed with the supplied future by
   * the time this method returns. If the supplied future is not done and the call is accepted, then
   * the future will be <i>set asynchronously</i>. Note that such a result, though not yet known,

   * elements. The generated map is sorted by the specified comparator.
   *
   * <p>If the mapped keys contain duplicates (according to the specified comparator), an {@code
   * IllegalArgumentException} is thrown when the collection operation is performed. (This differs
   * from the {@code Collector} returned by {@link Collectors#toMap(Function, Function)}, which
   * throws an {@code IllegalStateException}.)
   *
   * @since 21.0
   */

    // tells the computing thread when to start computing
    final CountDownLatch computeSignal = new CountDownLatch(1);
    // tells the main thread when computation is pending
    final CountDownLatch secondSignal = new CountDownLatch(1);
    // tells the main thread when the second get has started
    final CountDownLatch thirdSignal = new CountDownLatch(1);
    // tells the main thread when the third get has started

 */
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
/*
 * I have decided not to bother adding @ParametricNullness annotations in this class. Adding them is
 * a lot of busy work, and the annotation matters only when the APIs to be annotated are visible to
 * Kotlin code. In this class, nothing is publicly visible (nor exposed indirectly through a
 * publicly visible subclass), and I doubt any of our current or future Kotlin extensions for the

    }
    assertWithMessage("table size after adding " + size + " elements")
        .that(bucketsOf(map1))
        .isEqualTo(initialBuckets);

    /*
     * Something slightly different happens when the entries are added all at
     * once; make sure that passes too.
     */
    map2.putAll(map1);
    assertWithMessage("table size after adding " + size + " elements")
        .that(bucketsOf(map1))

    }
    assertWithMessage("table size after adding " + size + " elements")
        .that(bucketsOf(map1))
        .isEqualTo(initialBuckets);

    /*
     * Something slightly different happens when the entries are added all at
     * once; make sure that passes too.
     */
    map2.putAll(map1);
    assertWithMessage("table size after adding " + size + " elements")
        .that(bucketsOf(map1))

   *
   * // Falling back to a zero counter in case an exception happens when
   * // processing the RPC to fetch counters.
   * ListenableFuture<Integer> faultTolerantFuture = Futures.catching(
   *     fetchCounterFuture, FetchException.class, x -> 0, directExecutor());
   * }</pre>
   *
   * <p>When selecting an executor, note that {@code directExecutor} is dangerous in some cases. See