current.elemCount = 0;
        // Also clear these fields so that one deleted Entry doesn't retain all elements.
        current.left = null;
        current.right = null;
        current.pred = null;
        current.succ = null;

        current = next;
      }
      successor(header, header);
      rootReference.clear();
    } else {

  static <K, V> void nullifyWriteOrder(ReferenceEntry<K, V> nulled) {
    ReferenceEntry<K, V> nullEntry = nullEntry();
    nulled.setNextInWriteQueue(nullEntry);
    nulled.setPreviousInWriteQueue(nullEntry);
  }

  /**
   * Notifies listeners that an entry has been automatically removed due to expiration, eviction, or
   * eligibility for garbage collection. This should be called every time expireEntries or

      @ParametricNullness V value) {
    if (value == null) {
      // This cast is safe because null is assignable to V for all V (i.e. it is bivariant)
      @SuppressWarnings("unchecked")
      ListenableFuture<V> typedNull = (ListenableFuture<V>) ImmediateFuture.NULL;
      return typedNull;
    }
    return new ImmediateFuture<>(value);
  }

  /**

    lateinit var providedBy: Set<String>

    private
    lateinit var selected: String

    private
    var upgrade: String? = null

    internal
    fun configure(components: ComponentMetadataHandler, configurations: ConfigurationContainer) {
        if (upgrade != null) {
            configurations.forceUpgrade(selected, upgrade!!)
        } else {
            providedBy.forEachIndexed { idx, provider ->

  private <T extends Iterator<E>> void internalExecuteAndCompare(
      T reference, T target, IteratorOperation method) {
    Object referenceReturnValue = null;
    PermittedMetaException referenceException = null;
    Object targetReturnValue = null;
    Exception targetException = null;

    try {
      targetReturnValue = method.execute(target);
    } catch (Exception e) { // sneaky checked exception
      targetException = e;

  private <T extends Iterator<E>> void internalExecuteAndCompare(
      T reference, T target, IteratorOperation method) {
    Object referenceReturnValue = null;
    PermittedMetaException referenceException = null;
    Object targetReturnValue = null;
    Exception targetException = null;

    try {
      targetReturnValue = method.execute(target);
    } catch (Exception e) { // sneaky checked exception
      targetException = e;

    /*
     * Even though it's weird to pass a defaultValue that is null, some callers do so. Those who
     * pass a literal "null" should probably just use `get`, but I would expect other callers to
     * pass an expression that *might* be null. This could happen with:
     *
     * - a `getFooOrDefault(@Nullable Foo defaultValue)` method that returns

                calledFirst.set(true);
                assertFalse(called.get());
                QueryBuilder builder = chain.execute(context, query, boost);
                assertTrue(called.get());
                return builder;
            }
        });
        queryBuilder = queryProcessor.execute(context, query, 1.0f);
        assertTrue(called.get());
        assertTrue(calledFirst.get());

    secondFuture.cancel(true);
    assertThat(secondCallable.called).isFalse();
    assertThat(thirdCallable.called).isFalse();
    firstFuture.set(null);
    assertThat(secondCallable.called).isFalse();
    assertThat(thirdCallable.called).isTrue();
  }

  public void testCancellationMultipleThreads() throws Exception {

    secondFuture.cancel(true);
    assertThat(secondCallable.called).isFalse();
    assertThat(thirdCallable.called).isFalse();
    firstFuture.set(null);
    assertThat(secondCallable.called).isFalse();
    assertThat(thirdCallable.called).isTrue();
  }

  public void testCancellationMultipleThreads() throws Exception {