* if key or value objects already present in the multimap change in a manner that affects
 * {@code equals} comparisons. Use caution if mutable objects are used as keys or values in a {@code
 * SetMultimap}.
 *
 * <p><b>Warning:</b> Do not modify either a key <i>or a value</i> of a {@code SetMultimap} in a way

   * snapshot of the state and therefore it can be used to answer simple queries without needing to
   * grab a lock.
   */
  // @Immutable except that Throwable is mutable (initCause(), setStackTrace(), mutable subclasses).
  private static final class StateSnapshot {
    /**
     * The internal state, which equals external state unless shutdownWhenStartupFinishes is true.
     */
    final State state;

import java.util.Map;
import java.util.Set;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.NonNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A mutable type-to-instance map. See also {@link ImmutableTypeToInstanceMap}.
 *
 * @author Ben Yu
 * @since 13.0
 */
@ElementTypesAreNonnullByDefault
public final class MutableTypeToInstanceMap<B extends @Nullable Object>

      AvlNode<E> newRoot = new AvlNode<>(element, occurrences);
      successor(header, newRoot, header);
      rootReference.checkAndSet(root, newRoot);
      return 0;
    }
    int[] result = new int[1]; // used as a mutable int reference to hold result
    AvlNode<E> newRoot = root.add(comparator(), element, occurrences, result);
    rootReference.checkAndSet(root, newRoot);
    return result[0];
  }

  @CanIgnoreReturnValue

 */
public abstract class AbstractGraphTest {

  Graph<Integer> graph;

  /**
   * The same reference as {@link #graph}, except as a mutable graph. This field is null in case
   * {@link #createGraph()} didn't return a mutable graph.
   */
  MutableGraph<Integer> graphAsMutableGraph;

  static final Integer N1 = 1;
  static final Integer N2 = 2;
  static final Integer N3 = 3;

 *
 * <p>This class maintains a map of nodes to {@link GraphConnections}.
 *
 * <p>Collection-returning accessors return unmodifiable views: the view returned will reflect
 * changes to the graph (if the graph is mutable) but may not be modified by the user.
 *
 * <p>The time complexity of all collection-returning accessors is O(1), since views are returned.
 *
 * @author James Sexton
 * @author Joshua O'Madadhain
 * @author Omar Darwish

 * directed graphs, and an arbitrary endpoint of the edge on undirected graphs.
 *
 * <p>Collection-returning accessors return unmodifiable views: the view returned will reflect
 * changes to the graph (if the graph is mutable) but may not be modified by the user.
 *
 * <p>The time complexity of all collection-returning accessors is O(1), since views are returned.
 *
 * @author James Sexton
 * @author Joshua O'Madadhain
 * @author Omar Darwish

 * directed graphs, and an arbitrary endpoint of the edge on undirected graphs.
 *
 * <p>Collection-returning accessors return unmodifiable views: the view returned will reflect
 * changes to the graph (if the graph is mutable) but may not be modified by the user.
 *
 * <p>The time complexity of all collection-returning accessors is O(1), since views are returned.
 *
 * @author James Sexton
 * @author Joshua O'Madadhain
 * @author Omar Darwish

  boolean needsAllocArrays() {
    return table == null;
  }

  /** Handle lazy allocation of arrays. */
  @CanIgnoreReturnValue
  int allocArrays() {
    Preconditions.checkState(needsAllocArrays(), "Arrays already allocated");

    int expectedSize = metadata;
    int buckets = CompactHashing.tableSize(expectedSize);
    this.table = CompactHashing.createTable(buckets);

  }

  private static <T extends @Nullable Object> List<T> shuffledCopy(List<T> in, Random random) {
    List<T> mutable = newArrayList(in);
    List<T> out = newArrayList();
    while (!mutable.isEmpty()) {
      out.add(mutable.remove(random.nextInt(mutable.size())));
    }
    return out;
  }