001/*
002 * Copyright (C) 2016 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.graph;
018
019import static java.util.Objects.requireNonNull;
020
021import com.google.common.annotations.Beta;
022import com.google.common.collect.Maps;
023import java.util.Map;
024import java.util.Optional;
025import java.util.Set;
026import javax.annotation.CheckForNull;
027
028/**
029 * This class provides a skeletal implementation of {@link ValueGraph}. It is recommended to extend
030 * this class rather than implement {@link ValueGraph} directly.
031 *
032 * <p>The methods implemented in this class should not be overridden unless the subclass admits a
033 * more efficient implementation.
034 *
035 * @author James Sexton
036 * @param <N> Node parameter type
037 * @param <V> Value parameter type
038 * @since 20.0
039 */
040@Beta
041@ElementTypesAreNonnullByDefault
042public abstract class AbstractValueGraph<N, V> extends AbstractBaseGraph<N>
043    implements ValueGraph<N, V> {
044  /** Constructor for use by subclasses. */
045  public AbstractValueGraph() {}
046
047  @Override
048  public Graph<N> asGraph() {
049    return new AbstractGraph<N>() {
050      @Override
051      public Set<N> nodes() {
052        return AbstractValueGraph.this.nodes();
053      }
054
055      @Override
056      public Set<EndpointPair<N>> edges() {
057        return AbstractValueGraph.this.edges();
058      }
059
060      @Override
061      public boolean isDirected() {
062        return AbstractValueGraph.this.isDirected();
063      }
064
065      @Override
066      public boolean allowsSelfLoops() {
067        return AbstractValueGraph.this.allowsSelfLoops();
068      }
069
070      @Override
071      public ElementOrder<N> nodeOrder() {
072        return AbstractValueGraph.this.nodeOrder();
073      }
074
075      @Override
076      public ElementOrder<N> incidentEdgeOrder() {
077        return AbstractValueGraph.this.incidentEdgeOrder();
078      }
079
080      @Override
081      public Set<N> adjacentNodes(N node) {
082        return AbstractValueGraph.this.adjacentNodes(node);
083      }
084
085      @Override
086      public Set<N> predecessors(N node) {
087        return AbstractValueGraph.this.predecessors(node);
088      }
089
090      @Override
091      public Set<N> successors(N node) {
092        return AbstractValueGraph.this.successors(node);
093      }
094
095      @Override
096      public int degree(N node) {
097        return AbstractValueGraph.this.degree(node);
098      }
099
100      @Override
101      public int inDegree(N node) {
102        return AbstractValueGraph.this.inDegree(node);
103      }
104
105      @Override
106      public int outDegree(N node) {
107        return AbstractValueGraph.this.outDegree(node);
108      }
109    };
110  }
111
112  @Override
113  public Optional<V> edgeValue(N nodeU, N nodeV) {
114    return Optional.ofNullable(edgeValueOrDefault(nodeU, nodeV, null));
115  }
116
117  @Override
118  public Optional<V> edgeValue(EndpointPair<N> endpoints) {
119    return Optional.ofNullable(edgeValueOrDefault(endpoints, null));
120  }
121
122  @Override
123  public final boolean equals(@CheckForNull Object obj) {
124    if (obj == this) {
125      return true;
126    }
127    if (!(obj instanceof ValueGraph)) {
128      return false;
129    }
130    ValueGraph<?, ?> other = (ValueGraph<?, ?>) obj;
131
132    return isDirected() == other.isDirected()
133        && nodes().equals(other.nodes())
134        && edgeValueMap(this).equals(edgeValueMap(other));
135  }
136
137  @Override
138  public final int hashCode() {
139    return edgeValueMap(this).hashCode();
140  }
141
142  /** Returns a string representation of this graph. */
143  @Override
144  public String toString() {
145    return "isDirected: "
146        + isDirected()
147        + ", allowsSelfLoops: "
148        + allowsSelfLoops()
149        + ", nodes: "
150        + nodes()
151        + ", edges: "
152        + edgeValueMap(this);
153  }
154
155  private static <N, V> Map<EndpointPair<N>, V> edgeValueMap(final ValueGraph<N, V> graph) {
156    return Maps.asMap(
157        graph.edges(),
158        edge ->
159            // requireNonNull is safe because the endpoint pair comes from the graph.
160            requireNonNull(graph.edgeValueOrDefault(edge.nodeU(), edge.nodeV(), null)));
161  }
162}