this.supportsFastOffset = supportsFastOffset;
  }

  /**
   * Returns, conceptually, "origin + distance", or equivalently, the result of calling {@link
   * #next} on {@code origin} {@code distance} times.
   */
  C offset(C origin, long distance) {
    C current = origin;
    checkNonnegative(distance, "distance");
    for (long i = 0; i < distance; i++) {
      current = next(current);

  V removeSuccessor(N node);

  /**
   * Add {@code node} as a predecessor to the origin node. In the case of an undirected graph, it
   * also becomes a successor. Associates {@code value} with the edge connecting the two nodes.
   */
  void addPredecessor(N node, V value);

  /**
   * Add {@code node} as a successor to the origin node. In the case of an undirected graph, it also

    this.supportsFastOffset = supportsFastOffset;
  }

  /**
   * Returns, conceptually, "origin + distance", or equivalently, the result of calling {@link
   * #next} on {@code origin} {@code distance} times.
   */
  C offset(C origin, long distance) {
    C current = origin;
    checkNonnegative(distance, "distance");
    for (long i = 0; i < distance; i++) {
      current = next(current);

  Set<E> inEdges();

  Set<E> outEdges();

  /**
   * Returns the set of edges connecting the origin node to {@code node}. For networks without
   * parallel edges, this set cannot be of size greater than one.
   */
  Set<E> edgesConnecting(N node);

  /**
   * Returns the node that is adjacent to the origin node along {@code edge}.
   *
   * <p>In the directed case, {@code edge} is assumed to be an outgoing edge.
   */

   * returns an arbitrary (but consistent) endpoint of the origin edge.
   */
  public final N nodeU() {
    return nodeU;
  }

  /**
   * Returns the node {@link #adjacentNode(Object) adjacent} to {@link #nodeU()} along the origin
   * edge. If this {@link EndpointPair} {@link #isOrdered()}, this is equal to {@link #target()}.
   */
  public final N nodeV() {

      fail("www..google.com should have been invalid");
    } catch (IllegalArgumentException expected) {
    }
  }

  public void testParentChild() {
    InternetDomainName origin = InternetDomainName.from("foo.com");
    InternetDomainName parent = origin.parent();
    assertEquals("com", parent.toString());

    // These would throw an exception if leniency were not preserved during parent() and child()
    // calls.

import java.util.AbstractSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import javax.annotation.CheckForNull;

/**
 * A class to represent the set of edges connecting an (implicit) origin node to a target node.
 *
 * <p>The {@link #outEdgeToNode} map allows this class to work on networks with parallel edges. See
 * {@link EdgesConnecting} for a class that is more efficient but forbids parallel edges.
 *

 */
@ElementTypesAreNonnullByDefault
abstract class AbstractDirectedNetworkConnections<N, E> implements NetworkConnections<N, E> {
  /** Keys are edges incoming to the origin node, values are the source node. */
  final Map<E, N> inEdgeMap;

  /** Keys are edges outgoing from the origin node, values are the target node. */
  final Map<E, N> outEdgeMap;

  private int selfLoopCount;

      fail("www..google.com should have been invalid");
    } catch (IllegalArgumentException expected) {
    }
  }

  public void testParentChild() {
    InternetDomainName origin = InternetDomainName.from("foo.com");
    InternetDomainName parent = origin.parent();
    assertEquals("com", parent.toString());

    // These would throw an exception if leniency were not preserved during parent() and child()
    // calls.

      represent, as a whole, an original work of authorship. For the purposes
      of this License, Derivative Works shall not include works that remain
      separable from, or merely link (or bind by name) to the interfaces of,
      the Work and Derivative Works thereof.

      "Contribution" shall mean any work of authorship, including
      the original version of the Work and any modifications or additions