}

  @CanIgnoreReturnValue
  @Override
  @CheckForNull
  public E poll() {
    return isEmpty() ? null : removeAndGet(0);
  }

  @SuppressWarnings("unchecked") // we must carefully only allow Es to get in
  E elementData(int index) {
    /*
     * requireNonNull is safe as long as we're careful to call this method only with populated
     * indexes.
     */
    return (E) requireNonNull(queue[index]);

   * Creates a thread-safe set backed by a hash map. The set is backed by a {@link
   * ConcurrentHashMap} instance, and thus carries the same concurrency guarantees.
   *
   * <p>Unlike {@code HashSet}, this class does NOT allow {@code null} to be used as an element. The
   * set is serializable.
   *
   * @return a new, empty thread-safe {@code Set}
   * @since 15.0
   */
  public static <E> Set<E> newConcurrentHashSet() {

   * that entries are indexable using ints.
   */
  static final int MAXIMUM_CAPACITY = Ints.MAX_POWER_OF_TWO;

  /** The maximum number of segments to allow; used to bound constructor arguments. */
  static final int MAX_SEGMENTS = 1 << 16; // slightly conservative

  /** Number of (unsynchronized) retries in the containsValue method. */

    GraphBuilder<N1> castBuilder = cast();
    return new ImmutableGraph.Builder<>(castBuilder);
  }

  /**
   * Specifies whether the graph will allow self-loops (edges that connect a node to itself).
   * Attempting to add a self-loop to a graph that does not allow them will throw an {@link
   * UnsupportedOperationException}.
   *
   * <p>The default value is {@code false}.
   */
  @CanIgnoreReturnValue

      this.adder = adder;
    }

    @Override
    public int add(int a, int b) {
      try {
        return adder.add(a, b);
      } catch (Exception e) {
        // swallow!
        return 0;
      }
    }

    @Override
    public String toString() {
      return adder.toString();
    }
  }

  public interface Arithmetic extends Adder {

 * ClassToInstanceMap}</a>.
 *
 * @param <B> the common supertype that all values will share. When in doubt, just use {@link
 *     Object}, or use {@code @Nullable Object} to allow null values.
 * @since 2.0
 */
@DoNotMock("Use ImmutableClassToInstanceMap or MutableClassToInstanceMap")
@GwtCompatible
@ElementTypesAreNonnullByDefault
public interface ClassToInstanceMap<B extends @Nullable Object>

import java.util.Set;
import javax.annotation.CheckForNull;

/**
 * An empty contiguous set.
 *
 * @author Gregory Kick
 */
@GwtCompatible(emulated = true)
@SuppressWarnings("rawtypes") // allow ungenerified Comparable types
@ElementTypesAreNonnullByDefault
final class EmptyContiguousSet<C extends Comparable> extends ContiguousSet<C> {
  EmptyContiguousSet(DiscreteDomain<C> domain) {
    super(domain);
  }

  private final BaseGraph<N> graph;
  private final Iterator<N> nodeIterator;

  @CheckForNull
  N node = null; // null is safe as an initial value because graphs don't allow null nodes

  Iterator<N> successorIterator = ImmutableSet.<N>of().iterator();

  static <N> EndpointPairIterator<N> of(BaseGraph<N> graph) {
    return graph.isDirected() ? new Directed<N>(graph) : new Undirected<N>(graph);

          } else if (outputFuture.isCancelled() && taskExecutor.trySetCancelled()) {
            // If this CAS succeeds, we know that the provided callable will never be invoked,
            // so when oldFuture completes it is safe to allow the next submitted task to
            // proceed. Doing this immediately here lets the next task run without waiting for
            // the cancelled task's executor to run the noop AsyncCallable.
            //

        <!--
            In order to build and run the tests against JDK 18+, we need to pass java.security.manager=allow, to make
            the deprecated 'java.lang.SecurityManager' available for use.
         -->
        <jdk>[18,]</jdk>
      </activation>
      <properties>
        <test.add.args>-Djava.security.manager=allow</test.add.args>
      </properties>
    </profile>
  </profiles>