@J2ktIncompatible // serialization
  @GwtIncompatible // serialization
  Object writeReplace() {
    return super.writeReplace();
  }

  // No longer used for new writes, but kept so that old data can still be read.
  @GwtIncompatible // serialization
  @J2ktIncompatible
  @SuppressWarnings("unused")
  private static class SerializedForm<V> implements Serializable {
    final ImmutableMap<?, V> map;

     * 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
     * least old versions), so we mostly do. This is useful because we don't actually run our CI on
     * Windows under Java 8, at least as of this writing.
     *

            java: 21
            root-pom: pom.xml
    runs-on: ${{ matrix.os }}
    env:
      ROOT_POM: ${{ matrix.root-pom }}
    steps:
      # Cancel any previous runs for the same branch that are still running.
      - name: 'Cancel previous runs'
        uses: styfle/cancel-workflow-action@85880fa0301c86cca9da44039ee3bb12d3bedbfa # 0.12.1
        with:
          access_token: ${{ github.token }}

   * buildOrThrow(), or vice versa. So in particular, if we modify alternatingKeysAndValues to
   * eliminate duplicate keys (for buildKeepingLast()) then we have to ensure that a later call to
   * buildOrThrow() will still throw as if the duplicates had not been eliminated. And the exception
   * message must mention two values that were associated with the duplicate key in two different

          .put("MD5", Hashing.md5())
          .put("SHA", Hashing.sha1()) // Not the official name, but still works
          .put("SHA1", Hashing.sha1()) // Not the official name, but still works
          .put("sHa-1", Hashing.sha1()) // Not the official name, but still works
          .put("SHA-1", Hashing.sha1())
          .put("SHA-256", Hashing.sha256())
          .put("SHA-384", Hashing.sha384())

    assertEquals(
        "next() should still return first element after peeking", "A", peekingIterator.next());

    assertEquals("Should be able to peek() at middle element", "B", peekingIterator.peek());
    assertEquals(
        "Should be able to peek() middle element multiple times", "B", peekingIterator.peek());
    assertEquals(
        "next() should still return middle element after peeking", "B", peekingIterator.next());

  /**
   * Returns a {@link ScheduledExecutorService} that never executes anything.
   *
   * <p>The {@code shutdownNow} method of the returned executor always returns an empty list despite
   * the fact that everything is still technically awaiting execution. The {@code getDelay} method
   * of any {@link ScheduledFuture} returned by the executor will always return the max long value
   * instead of the time until the user-specified delay.
   */

    for (LoadingCache<Object, Object> cache : caches()) {
      cache.getUnchecked(1);
      cache.getUnchecked(2);

      Set<Object> keys = cache.asMap().keySet();
      // We don't know whether these are still in the cache, so we can't assert on the return
      // values of these removes, but the cache should be empty after the removes, regardless.
      keys.remove(1);
      keys.remove(2);
      assertFalse(keys.remove(null));

   * trouble than just using Object.class.)
   *
   * Then we declare the getters for these fields as @GwtIncompatible so that no one can try to use
   * them under J2CL—or, as an unfortunate side effect, under GWT. We do still give the fields
   * themselves their proper values under GWT, since GWT's EnumMap does need the Class instance.
   *
   * Note that sometimes these fields *do* have correct values under J2CL: They will if the caller

 *     }
 *     value = newValue;
 *     notifyAll();
 *   }
 * }
 * }</pre>
 *
 * <h3>{@code ReentrantLock}</h3>
 *
 * <p>This version is much more verbose than the {@code synchronized} version, and still suffers
 * from the need for the programmer to remember to use {@code while} instead of {@code if}. However,
 * one advantage is that we can introduce two separate {@code Condition} objects, which allows us to