import java.util.Collections;
import java.util.Map;
import java.util.Set;
import org.jspecify.annotations.Nullable;

/**
 * A base implementation of {@link NetworkConnections} for directed networks.
 *
 * @author James Sexton
 * @param <N> Node parameter type
 * @param <E> Edge parameter type
 */
abstract class AbstractDirectedNetworkConnections<N, E> implements NetworkConnections<N, E> {

 */

package com.google.common.graph;

import com.google.common.base.Optional;

/**
 * A base class for builders that construct graphs with user-defined properties.
 *
 * @author James Sexton
 */
abstract class AbstractGraphBuilder<N> {
  final boolean directed;
  boolean allowsSelfLoops = false;
  ElementOrder<N> nodeOrder = ElementOrder.insertion();

import org.jspecify.annotations.Nullable;

/**
 * This class provides a skeletal implementation of {@link Graph}. It is recommended to extend this
 * class rather than implement {@link Graph} directly.
 *
 * @author James Sexton
 * @param <N> Node parameter type
 * @since 20.0
 */
@Beta
public abstract class AbstractGraph<N> extends AbstractBaseGraph<N> implements Graph<N> {
  /** Constructor for use by subclasses. */

 *         .putEdgeValue("San Jose", "San Jose", 0.0)
 *         .putEdgeValue("San Francisco", "San Jose", 48.4)
 *         .build();
 * }
 *
 * @author James Sexton
 * @author Joshua O'Madadhain
 * @param <N> The most general node type this builder will support. This is normally {@code Object}
 *     unless it is constrained by using a method like {@link #nodeOrder}, or the builder is

 *
 * <p>The {@link #nodeToOutEdge} map means this class only works on networks without parallel edges.
 * See {@link MultiEdgesConnecting} for a class that works with parallel edges.
 *
 * @author James Sexton
 * @param <E> Edge parameter type
 */
final class EdgesConnecting<E> extends AbstractSet<E> {

  private final Map<?, E> nodeToOutEdge;
  private final Object targetNode;

import java.util.Set;

/**
 * A class to allow {@link Graph} implementations to be backed by a {@link BaseGraph}. This is not
 * currently planned to be released as a general-purpose forwarding class.
 *
 * @author James Sexton
 */
abstract class ForwardingGraph<N> extends AbstractGraph<N> {

  abstract BaseGraph<N> delegate();

  @Override
  public Set<N> nodes() {
    return delegate().nodes();
  }

  /**

import java.util.Set;

/**
 * A class to allow {@link Graph} implementations to be backed by a {@link BaseGraph}. This is not
 * currently planned to be released as a general-purpose forwarding class.
 *
 * @author James Sexton
 */
abstract class ForwardingGraph<N> extends AbstractGraph<N> {

  abstract BaseGraph<N> delegate();

  @Override
  public Set<N> nodes() {
    return delegate().nodes();
  }

  /**

import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
import org.jspecify.annotations.Nullable;

/**
 * An implementation of {@link GraphConnections} for undirected graphs.
 *
 * @author James Sexton
 * @param <N> Node parameter type
 * @param <V> Value parameter type
 */
final class UndirectedGraphConnections<N, V> implements GraphConnections<N, V> {
  private final Map<N, V> adjacentNodeValues;

import java.util.Map;
import java.util.Set;
import org.jspecify.annotations.Nullable;

/**
 * An implementation of {@link NetworkConnections} for undirected networks with parallel edges.
 *
 * @author James Sexton
 * @param <N> Node parameter type
 * @param <E> Edge parameter type
 */
final class UndirectedMultiNetworkConnections<N, E>
    extends AbstractUndirectedNetworkConnections<N, E> {

 *
 * <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.
 *
 * @author James Sexton
 * @param <E> Edge parameter type
 */
abstract class MultiEdgesConnecting<E> extends AbstractSet<E> {

  private final Map<E, ?> outEdgeToNode;
  private final Object targetNode;