* #enqueue enqueued} and {@link #dispatch dispatched}.
   */
  public void addListener(L listener, Executor executor) {
    checkNotNull(listener, "listener");
    checkNotNull(executor, "executor");
    listeners.add(new PerListenerQueue<>(listener, executor));
  }

  /**
   * Enqueues an event to be run on currently known listeners.
   *

  @J2ktIncompatible
  @GwtIncompatible
  public static <T extends @Nullable Object> AsyncCallable<T> asAsyncCallable(
      Callable<T> callable, ListeningExecutorService listeningExecutorService) {
    checkNotNull(callable);
    checkNotNull(listeningExecutorService);
    return () -> listeningExecutorService.submit(callable);
  }

  /**
   * Wraps the given callable such that for the duration of {@link Callable#call} the thread that is

 * the License.
 */

package com.google.common.util.concurrent;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static java.util.Objects.requireNonNull;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;

   * new entry with those values.
   */
  static <R, C, V> Cell<R, C, V> cellOf(R rowKey, C columnKey, V value) {
    return immutableCell(
        checkNotNull(rowKey, "rowKey"),
        checkNotNull(columnKey, "columnKey"),
        checkNotNull(value, "value"));
  }

  /**
   * A builder for creating immutable table instances, especially {@code public static final} tables
   * ("constant tables"). Example:

    }

    return new FilteredCollection<>(checkNotNull(unfiltered), checkNotNull(predicate));
  }

  /**
   * Delegates to {@link Collection#contains}. Returns {@code false} if the {@code contains} method
   * throws a {@code ClassCastException} or {@code NullPointerException}.
   */
  static boolean safeContains(Collection<?> collection, @CheckForNull Object object) {
    checkNotNull(collection);
    try {

    return headSetImpl(checkNotNull(toElement), false);
  }

  /** @since 12.0 */
  @GwtIncompatible // NavigableSet
  @Override
  public ContiguousSet<C> headSet(C toElement, boolean inclusive) {
    return headSetImpl(checkNotNull(toElement), inclusive);
  }

  @Override
  public ContiguousSet<C> subSet(C fromElement, C toElement) {
    checkNotNull(fromElement);
    checkNotNull(toElement);

  }

  @Override
  public T or(T defaultValue) {
    return checkNotNull(defaultValue, "use Optional.orNull() instead of Optional.or(null)");
  }

  @SuppressWarnings("unchecked") // safe covariant cast
  @Override
  public Optional<T> or(Optional<? extends T> secondChoice) {
    return (Optional<T>) checkNotNull(secondChoice);
  }

  @Override
  public T or(Supplier<? extends T> supplier) {

  }

  @Override
  public T or(T defaultValue) {
    checkNotNull(defaultValue, "use Optional.orNull() instead of Optional.or(null)");
    return reference;
  }

  @Override
  public Optional<T> or(Optional<? extends T> secondChoice) {
    checkNotNull(secondChoice);
    return this;
  }

  @Override
  public T or(Supplier<? extends T> supplier) {
    checkNotNull(supplier);
    return reference;
  }

  @Override

    @Override
    public SortedMap<C, V> subMap(C fromKey, C toKey) {
      checkArgument(rangeContains(checkNotNull(fromKey)) && rangeContains(checkNotNull(toKey)));
      return new TreeRow(rowKey, fromKey, toKey);
    }

    @Override
    public SortedMap<C, V> headMap(C toKey) {
      checkArgument(rangeContains(checkNotNull(toKey)));
      return new TreeRow(rowKey, lowerBound, toKey);
    }

    @Override

  }

  static <N, V> DirectedGraphConnections<N, V> ofImmutable(
      N thisNode, Iterable<EndpointPair<N>> incidentEdges, Function<N, V> successorNodeToValueFn) {
    checkNotNull(thisNode);
    checkNotNull(successorNodeToValueFn);

    Map<N, Object> adjacentNodeValues = new HashMap<>();
    ImmutableList.Builder<NodeConnection<N>> orderedNodeConnectionsBuilder =
        ImmutableList.builder();