final MapIteratorCache<N, GraphConnections<N, V>> nodeConnections;

  long edgeCount; // must be updated when edges are added or removed

  /** Constructs a graph with the properties specified in {@code builder}. */
  StandardValueGraph(AbstractGraphBuilder<? super N> builder) {
    this(
        builder,
        builder.nodeOrder.<N, GraphConnections<N, V>>createMap(

import javax.annotation.CheckForNull;

/**
 * An implementation of {@link GraphConnections} for directed graphs.
 *
 * @author James Sexton
 * @author Jens Nyman
 * @param <N> Node parameter type
 * @param <V> Value parameter type
 */
@ElementTypesAreNonnullByDefault
final class DirectedGraphConnections<N, V> implements GraphConnections<N, V> {
  /**