abstract @Nullable Waiter gasWaiters(AbstractFutureState<?> future, Waiter update);

    /** Performs a GAS operation on {@link AbstractFutureState#listenersField}. */
    abstract @Nullable Listener gasListeners(AbstractFutureState<?> future, Listener update);

    /** Performs a CAS operation on {@link AbstractFutureState#valueField}. */
    abstract boolean casValue(

import com.google.common.util.concurrent.AbstractFuture.Listener;
import com.google.common.util.concurrent.internal.InternalFutureFailureAccess;
import org.jspecify.annotations.Nullable;

abstract class AbstractFutureState<V extends @Nullable Object> extends InternalFutureFailureAccess
    implements ListenableFuture<V> {
  final boolean casListeners(@Nullable Listener expect, Listener update) {
    if (listeners == expect) {

public class AbstractFutureDefaultAtomicHelperTest extends TestCase {
  public void testUsingExpectedAtomicHelper() throws Exception {
    if (isAndroid()) {
      assertThat(AbstractFutureState.atomicHelperTypeForTest()).isEqualTo("UnsafeAtomicHelper");
    } else {
      assertThat(AbstractFutureState.atomicHelperTypeForTest())
          .isEqualTo("AtomicReferenceFieldUpdaterAtomicHelper");
    }
  }

  private static boolean isJava8() {

  public void testUsingExpectedAtomicHelper() throws Exception {
    if (isJava8() || isAndroid()) {
      assertThat(AbstractFutureState.atomicHelperTypeForTest()).isEqualTo("UnsafeAtomicHelper");
    } else {
      assertThat(AbstractFutureState.atomicHelperTypeForTest()).isEqualTo("VarHandleAtomicHelper");
    }
  }

  private static boolean isJava8() {

     * AggregateFutureStateFallbackAtomicHelperTest, as discussed in a comment in
     * AggregateFutureState.
     *
     * Here, we check that we're able to force AbstractFutureState to select SynchronizedHelper, and
     * below, we actually run the AbstractFutureTest methods under that scenario.
     */
    checkHelperVersion(NO_ATOMIC_REFERENCE_FIELD_UPDATER, "SynchronizedHelper");

    extends AbstractFuture.TrustedFuture<OutputT> {
  /*
   * The following fields are package-private, even though we intend never to use them outside this
   * file. For discussion, see AbstractFutureState.
   */

  // Lazily initialized the first time we see an exception; not released until all the input futures
  // have completed and we have processed them all.

 */
@ReflectionSupport(value = ReflectionSupport.Level.FULL)
public abstract class AbstractFuture<V extends @Nullable Object> extends AbstractFutureState<V> {
  /*
   * All static initialization should be performed in AbstractFutureState: AbstractFutureState's
   * initialization may trigger logging, which may assume that AbstractFuture is initialized.
   *

      throws Exception {
    // Make sure we are actually running with the expected helper implementation
    Class<?> abstractFutureStateClass = classLoader.loadClass(AbstractFutureState.class.getName());
    Method helperMethod = abstractFutureStateClass.getDeclaredMethod("atomicHelperTypeForTest");
    helperMethod.setAccessible(true);