import java.util.concurrent.Executor;
import java.util.concurrent.Future;
import java.util.concurrent.RejectedExecutionException;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@link Future} that accepts completion listeners. Each listener has an associated executor, and
 * it is invoked using this executor once the future's computation is {@linkplain Future#isDone()

import java.util.concurrent.Executor;
import java.util.concurrent.Future;
import java.util.concurrent.RejectedExecutionException;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@link Future} that accepts completion listeners. Each listener has an associated executor, and
 * it is invoked using this executor once the future's computation is {@linkplain Future#isDone()

    private final ListenableFuture<@Nullable Void> future;
    private boolean called = false;

    private TestCallable(ListenableFuture<@Nullable Void> future) {
      this.future = future;
    }

    @Override
    public ListenableFuture<@Nullable Void> call() throws Exception {
      called = true;
      return future;
    }
  }

 *       Future} is "completed" even if it is cancelled while its underlying work continues on a
 *       thread, an RPC, etc. The {@code Future} is also "completed" if it fails "early" -- for
 *       example, if the deadline expires on a {@code Future} returned from {@link
 *       Futures#withTimeout} while the {@code Future} it wraps continues its underlying work. So

  * The `--audit-policy-file` option is required if the `AdvancedAuditing` feature is not explicitly turned off (`--feature-gates=AdvancedAuditing=false`) on the API server.
  * The audit log file defaults to JSON encoding when using the advanced auditing feature gate.
  * An audit policy file without either an `apiVersion` or a `kind` field may be treated as invalid.

    // TODO: test whether null is supported (create a Feature)
    /**
     * The elements to be returned by future calls to {@code next()}, with the first at the top of
     * the stack.
     */
    final Stack<E> nextElements = new Stack<>();

    /**
     * The elements to be returned by future calls to {@code previous()}, with the first at the top
     * of the stack.
     */

@GwtCompatible
public class ConflictingRequirementsException extends Exception {
  private Set<Feature<?>> conflicts;
  private Object source;

  public ConflictingRequirementsException(
      String message, Set<Feature<?>> conflicts, Object source) {
    super(message);
    this.conflicts = conflicts;
    this.source = source;
  }

  public Set<Feature<?>> getConflicts() {
    return conflicts;
  }

  public Object getSource() {

import com.google.common.collect.testing.DerivedCollectionGenerators.SortedSetSubsetTestSetGenerator;
import com.google.common.collect.testing.features.CollectionFeature;
import com.google.common.collect.testing.features.Feature;
import com.google.common.collect.testing.testers.CollectionAddAllTester;
import com.google.common.collect.testing.testers.CollectionAddTester;
import com.google.common.collect.testing.testers.SortedSetNavigationTester;

import com.google.common.collect.testing.DerivedCollectionGenerators.SortedSetSubsetTestSetGenerator;
import com.google.common.collect.testing.features.CollectionFeature;
import com.google.common.collect.testing.features.Feature;
import com.google.common.collect.testing.testers.CollectionAddAllTester;
import com.google.common.collect.testing.testers.CollectionAddTester;
import com.google.common.collect.testing.testers.SortedSetNavigationTester;

  private final FluentFuture<V> future;

  private ClosingFuture(ListenableFuture<V> future) {
    this(future, new CloseableList());
  }

  private ClosingFuture(ListenableFuture<V> future, CloseableList closeables) {
    this.future = FluentFuture.from(future);
    this.closeables = closeables;
  }

  /**