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.Set;
025import javax.annotation.CheckForNull;
026
027/**
028 * This class provides a skeletal implementation of {@link ValueGraph}. It is recommended to extend
029 * this class rather than implement {@link ValueGraph} directly.
030 *
031 * <p>The methods implemented in this class should not be overridden unless the subclass admits a
032 * more efficient implementation.
033 *
034 * @author James Sexton
035 * @param <N> Node parameter type
036 * @param <V> Value parameter type
037 * @since 20.0
038 */
039@Beta
040@ElementTypesAreNonnullByDefault
041public abstract class AbstractValueGraph<N, V> extends AbstractBaseGraph<N>
042    implements ValueGraph<N, V> {
043  /** Constructor for use by subclasses. */
044  public AbstractValueGraph() {}
045
046  @Override
047  public Graph<N> asGraph() {
048    return new AbstractGraph<N>() {
049      @Override
050      public Set<N> nodes() {
051        return AbstractValueGraph.this.nodes();
052      }
053
054      @Override
055      public Set<EndpointPair<N>> edges() {
056        return AbstractValueGraph.this.edges();
057      }
058
059      @Override
060      public boolean isDirected() {
061        return AbstractValueGraph.this.isDirected();
062      }
063
064      @Override
065      public boolean allowsSelfLoops() {
066        return AbstractValueGraph.this.allowsSelfLoops();
067      }
068
069      @Override
070      public ElementOrder<N> nodeOrder() {
071        return AbstractValueGraph.this.nodeOrder();
072      }
073
074      @Override
075      public ElementOrder<N> incidentEdgeOrder() {
076        return AbstractValueGraph.this.incidentEdgeOrder();
077      }
078
079      @Override
080      public Set<N> adjacentNodes(N node) {
081        return AbstractValueGraph.this.adjacentNodes(node);
082      }
083
084      @Override
085      public Set<N> predecessors(N node) {
086        return AbstractValueGraph.this.predecessors(node);
087      }
088
089      @Override
090      public Set<N> successors(N node) {
091        return AbstractValueGraph.this.successors(node);
092      }
093
094      @Override
095      public int degree(N node) {
096        return AbstractValueGraph.this.degree(node);
097      }
098
099      @Override
100      public int inDegree(N node) {
101        return AbstractValueGraph.this.inDegree(node);
102      }
103
104      @Override
105      public int outDegree(N node) {
106        return AbstractValueGraph.this.outDegree(node);
107      }
108    };
109  }
110
111  @Override
112  public final boolean equals(@CheckForNull Object obj) {
113    if (obj == this) {
114      return true;
115    }
116    if (!(obj instanceof ValueGraph)) {
117      return false;
118    }
119    ValueGraph<?, ?> other = (ValueGraph<?, ?>) obj;
120
121    return isDirected() == other.isDirected()
122        && nodes().equals(other.nodes())
123        && edgeValueMap(this).equals(edgeValueMap(other));
124  }
125
126  @Override
127  public final int hashCode() {
128    return edgeValueMap(this).hashCode();
129  }
130
131  /** Returns a string representation of this graph. */
132  @Override
133  public String toString() {
134    return "isDirected: "
135        + isDirected()
136        + ", allowsSelfLoops: "
137        + allowsSelfLoops()
138        + ", nodes: "
139        + nodes()
140        + ", edges: "
141        + edgeValueMap(this);
142  }
143
144  private static <N, V> Map<EndpointPair<N>, V> edgeValueMap(final ValueGraph<N, V> graph) {
145    return Maps.asMap(
146        graph.edges(),
147        edge ->
148            // requireNonNull is safe because the endpoint pair comes from the graph.
149            requireNonNull(graph.edgeValueOrDefault(edge.nodeU(), edge.nodeV(), null)));
150  }
151}