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/*
 * Copyright (C) 2017 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.graph;

import java.util.Set;

/**
 * A non-public interface for the methods shared between {@link Graph} and {@link ValueGraph}.
 *
 * @author James Sexton
 * @param  Node parameter type
 */
interface BaseGraph extends SuccessorsFunction, PredecessorsFunction {
  //
  // Graph-level accessors
  //

  /** Returns all nodes in this graph, in the order specified by {@link #nodeOrder()}. */
  Set nodes();

  /** Returns all edges in this graph. */
  Set> edges();

  //
  // Graph properties
  //

  /**
   * Returns true if the edges in this graph are directed. Directed edges connect a {@link
   * EndpointPair#source() source node} to a {@link EndpointPair#target() target node}, while
   * undirected edges connect a pair of nodes to each other.
   */
  boolean isDirected();

  /**
   * Returns true if this graph allows 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
   * IllegalArgumentException}.
   */
  boolean allowsSelfLoops();

  /** Returns the order of iteration for the elements of {@link #nodes()}. */
  ElementOrder nodeOrder();

  //
  // Element-level accessors
  //

  /**
   * Returns the nodes which have an incident edge in common with {@code node} in this graph.
   *
   * 

This is equal to the union of {@link #predecessors(Object)} and {@link #successors(Object)}. * * @throws IllegalArgumentException if {@code node} is not an element of this graph */ Set adjacentNodes(N node); /** * Returns all nodes in this graph adjacent to {@code node} which can be reached by traversing * {@code node}'s incoming edges against the direction (if any) of the edge. * *

In an undirected graph, this is equivalent to {@link #adjacentNodes(Object)}. * * @throws IllegalArgumentException if {@code node} is not an element of this graph */ @Override Set predecessors(N node); /** * Returns all nodes in this graph adjacent to {@code node} which can be reached by traversing * {@code node}'s outgoing edges in the direction (if any) of the edge. * *

In an undirected graph, this is equivalent to {@link #adjacentNodes(Object)}. * *

This is not the same as "all nodes reachable from {@code node} by following outgoing * edges". For that functionality, see {@link Graphs#reachableNodes(Graph, Object)}. * * @throws IllegalArgumentException if {@code node} is not an element of this graph */ @Override Set successors(N node); /** * Returns the edges in this graph whose endpoints include {@code node}. * *

This is equal to the union of incoming and outgoing edges. * * @throws IllegalArgumentException if {@code node} is not an element of this graph * @since 24.0 */ Set> incidentEdges(N node); /** * Returns the count of {@code node}'s incident edges, counting self-loops twice (equivalently, * the number of times an edge touches {@code node}). * *

For directed graphs, this is equal to {@code inDegree(node) + outDegree(node)}. * *

For undirected graphs, this is equal to {@code incidentEdges(node).size()} + (number of * self-loops incident to {@code node}). * *

If the count is greater than {@code Integer.MAX_VALUE}, returns {@code Integer.MAX_VALUE}. * * @throws IllegalArgumentException if {@code node} is not an element of this graph */ int degree(N node); /** * Returns the count of {@code node}'s incoming edges (equal to {@code predecessors(node).size()}) * in a directed graph. In an undirected graph, returns the {@link #degree(Object)}. * *

If the count is greater than {@code Integer.MAX_VALUE}, returns {@code Integer.MAX_VALUE}. * * @throws IllegalArgumentException if {@code node} is not an element of this graph */ int inDegree(N node); /** * Returns the count of {@code node}'s outgoing edges (equal to {@code successors(node).size()}) * in a directed graph. In an undirected graph, returns the {@link #degree(Object)}. * *

If the count is greater than {@code Integer.MAX_VALUE}, returns {@code Integer.MAX_VALUE}. * * @throws IllegalArgumentException if {@code node} is not an element of this graph */ int outDegree(N node); /** * Returns true if there is an edge that directly connects {@code nodeU} to {@code nodeV}. This is * equivalent to {@code nodes().contains(nodeU) && successors(nodeU).contains(nodeV)}. * *

In an undirected graph, this is equal to {@code hasEdgeConnecting(nodeV, nodeU)}. * * @since 23.0 */ boolean hasEdgeConnecting(N nodeU, N nodeV); /** * Returns true if there is an edge that directly connects {@code endpoints} (in the order, if * any, specified by {@code endpoints}). This is equivalent to {@code * edges().contains(endpoints)}. * *

Unlike the other {@code EndpointPair}-accepting methods, this method does not throw if the * endpoints are unordered; it simply returns false. This is for consistency with the behavior of * {@link Collection#contains(Object)} (which does not generally throw if the object cannot be * present in the collection), and the desire to have this method's behavior be compatible with * {@code edges().contains(endpoints)}. * * @since 27.1 */ boolean hasEdgeConnecting(EndpointPair endpoints); }





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