001/* 002 * Copyright (C) 2014 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 com.google.common.base.Preconditions.checkNotNull; 020 021import com.google.common.annotations.Beta; 022import com.google.common.base.Function; 023import com.google.common.collect.ImmutableMap; 024import com.google.common.collect.Maps; 025import com.google.errorprone.annotations.CanIgnoreReturnValue; 026import com.google.errorprone.annotations.Immutable; 027import java.util.Map; 028 029/** 030 * A {@link Network} whose elements and structural relationships will never change. Instances of 031 * this class may be obtained with {@link #copyOf(Network)}. 032 * 033 * <p>See the Guava User's Guide's <a 034 * href="https://github.com/google/guava/wiki/GraphsExplained#immutable-implementations">discussion 035 * of the {@code Immutable*} types</a> for more information on the properties and guarantees 036 * provided by this class. 037 * 038 * @author James Sexton 039 * @author Joshua O'Madadhain 040 * @author Omar Darwish 041 * @author Jens Nyman 042 * @param <N> Node parameter type 043 * @param <E> Edge parameter type 044 * @since 20.0 045 */ 046@Beta 047@Immutable(containerOf = {"N", "E"}) 048@SuppressWarnings("Immutable") // Extends ConfigurableNetwork but uses ImmutableMaps. 049public final class ImmutableNetwork<N, E> extends ConfigurableNetwork<N, E> { 050 051 private ImmutableNetwork(Network<N, E> network) { 052 super( 053 NetworkBuilder.from(network), getNodeConnections(network), getEdgeToReferenceNode(network)); 054 } 055 056 /** Returns an immutable copy of {@code network}. */ 057 public static <N, E> ImmutableNetwork<N, E> copyOf(Network<N, E> network) { 058 return (network instanceof ImmutableNetwork) 059 ? (ImmutableNetwork<N, E>) network 060 : new ImmutableNetwork<N, E>(network); 061 } 062 063 /** 064 * Simply returns its argument. 065 * 066 * @deprecated no need to use this 067 */ 068 @Deprecated 069 public static <N, E> ImmutableNetwork<N, E> copyOf(ImmutableNetwork<N, E> network) { 070 return checkNotNull(network); 071 } 072 073 @Override 074 public ImmutableGraph<N> asGraph() { 075 return new ImmutableGraph<N>(super.asGraph()); // safe because the view is effectively immutable 076 } 077 078 private static <N, E> Map<N, NetworkConnections<N, E>> getNodeConnections(Network<N, E> network) { 079 // ImmutableMap.Builder maintains the order of the elements as inserted, so the map will have 080 // whatever ordering the network's nodes do, so ImmutableSortedMap is unnecessary even if the 081 // input nodes are sorted. 082 ImmutableMap.Builder<N, NetworkConnections<N, E>> nodeConnections = ImmutableMap.builder(); 083 for (N node : network.nodes()) { 084 nodeConnections.put(node, connectionsOf(network, node)); 085 } 086 return nodeConnections.build(); 087 } 088 089 private static <N, E> Map<E, N> getEdgeToReferenceNode(Network<N, E> network) { 090 // ImmutableMap.Builder maintains the order of the elements as inserted, so the map will have 091 // whatever ordering the network's edges do, so ImmutableSortedMap is unnecessary even if the 092 // input edges are sorted. 093 ImmutableMap.Builder<E, N> edgeToReferenceNode = ImmutableMap.builder(); 094 for (E edge : network.edges()) { 095 edgeToReferenceNode.put(edge, network.incidentNodes(edge).nodeU()); 096 } 097 return edgeToReferenceNode.build(); 098 } 099 100 private static <N, E> NetworkConnections<N, E> connectionsOf(Network<N, E> network, N node) { 101 if (network.isDirected()) { 102 Map<E, N> inEdgeMap = Maps.asMap(network.inEdges(node), sourceNodeFn(network)); 103 Map<E, N> outEdgeMap = Maps.asMap(network.outEdges(node), targetNodeFn(network)); 104 int selfLoopCount = network.edgesConnecting(node, node).size(); 105 return network.allowsParallelEdges() 106 ? DirectedMultiNetworkConnections.ofImmutable(inEdgeMap, outEdgeMap, selfLoopCount) 107 : DirectedNetworkConnections.ofImmutable(inEdgeMap, outEdgeMap, selfLoopCount); 108 } else { 109 Map<E, N> incidentEdgeMap = 110 Maps.asMap(network.incidentEdges(node), adjacentNodeFn(network, node)); 111 return network.allowsParallelEdges() 112 ? UndirectedMultiNetworkConnections.ofImmutable(incidentEdgeMap) 113 : UndirectedNetworkConnections.ofImmutable(incidentEdgeMap); 114 } 115 } 116 117 private static <N, E> Function<E, N> sourceNodeFn(final Network<N, E> network) { 118 return new Function<E, N>() { 119 @Override 120 public N apply(E edge) { 121 return network.incidentNodes(edge).source(); 122 } 123 }; 124 } 125 126 private static <N, E> Function<E, N> targetNodeFn(final Network<N, E> network) { 127 return new Function<E, N>() { 128 @Override 129 public N apply(E edge) { 130 return network.incidentNodes(edge).target(); 131 } 132 }; 133 } 134 135 private static <N, E> Function<E, N> adjacentNodeFn(final Network<N, E> network, final N node) { 136 return new Function<E, N>() { 137 @Override 138 public N apply(E edge) { 139 return network.incidentNodes(edge).adjacentNode(node); 140 } 141 }; 142 } 143 144 /** 145 * A builder for creating {@link ImmutableNetwork} instances, especially {@code static final} 146 * networks. Example: 147 * 148 * <pre>{@code 149 * static final ImmutableNetwork<City, Train> TRAIN_NETWORK = 150 * NetworkBuilder.undirected() 151 * .allowsParallelEdges(true) 152 * .<City, Train>immutable() 153 * .addEdge(PARIS, BRUSSELS, Thalys.trainNumber("1111")) 154 * .addEdge(PARIS, BRUSSELS, RegionalTrain.trainNumber("2222")) 155 * .addEdge(LONDON, PARIS, Eurostar.trainNumber("3333")) 156 * .addEdge(LONDON, BRUSSELS, Eurostar.trainNumber("4444")) 157 * .addNode(REYKJAVIK) 158 * .build(); 159 * }</pre> 160 * 161 * <p>Builder instances can be reused; it is safe to call {@link #build} multiple times to build 162 * multiple networks in series. Each new network contains all the elements of the ones created 163 * before it. 164 * 165 * @since 28.0 166 */ 167 public static class Builder<N, E> { 168 169 private final MutableNetwork<N, E> mutableNetwork; 170 171 Builder(NetworkBuilder<N, E> networkBuilder) { 172 this.mutableNetwork = networkBuilder.build(); 173 } 174 175 /** 176 * Adds {@code node} if it is not already present. 177 * 178 * <p><b>Nodes must be unique</b>, just as {@code Map} keys must be. They must also be non-null. 179 * 180 * @return this {@code Builder} object 181 */ 182 @CanIgnoreReturnValue 183 public ImmutableNetwork.Builder<N, E> addNode(N node) { 184 mutableNetwork.addNode(node); 185 return this; 186 } 187 188 /** 189 * Adds {@code edge} connecting {@code nodeU} to {@code nodeV}. 190 * 191 * <p>If the network is directed, {@code edge} will be directed in this network; otherwise, it 192 * will be undirected. 193 * 194 * <p><b>{@code edge} must be unique to this network</b>, just as a {@code Map} key must be. It 195 * must also be non-null. 196 * 197 * <p>If {@code nodeU} and {@code nodeV} are not already present in this network, this method 198 * will silently {@link #addNode(Object) add} {@code nodeU} and {@code nodeV} to the network. 199 * 200 * <p>If {@code edge} already connects {@code nodeU} to {@code nodeV} (in the specified order if 201 * this network {@link #isDirected()}, else in any order), then this method will have no effect. 202 * 203 * @return this {@code Builder} object 204 * @throws IllegalArgumentException if {@code edge} already exists in the network and does not 205 * connect {@code nodeU} to {@code nodeV} 206 * @throws IllegalArgumentException if the introduction of the edge would violate {@link 207 * #allowsParallelEdges()} or {@link #allowsSelfLoops()} 208 */ 209 @CanIgnoreReturnValue 210 public ImmutableNetwork.Builder<N, E> addEdge(N nodeU, N nodeV, E edge) { 211 mutableNetwork.addEdge(nodeU, nodeV, edge); 212 return this; 213 } 214 215 /** 216 * Adds {@code edge} connecting {@code endpoints}. In an undirected network, {@code edge} will 217 * also connect {@code nodeV} to {@code nodeU}. 218 * 219 * <p>If this network is directed, {@code edge} will be directed in this network; if it is 220 * undirected, {@code edge} will be undirected in this network. 221 * 222 * <p>If this network is directed, {@code endpoints} must be ordered. 223 * 224 * <p><b>{@code edge} must be unique to this network</b>, just as a {@code Map} key must be. It 225 * must also be non-null. 226 * 227 * <p>If either or both endpoints are not already present in this network, this method will 228 * silently {@link #addNode(Object) add} each missing endpoint to the network. 229 * 230 * <p>If {@code edge} already connects an endpoint pair equal to {@code endpoints}, then this 231 * method will have no effect. 232 * 233 * @return this {@code Builder} object 234 * @throws IllegalArgumentException if {@code edge} already exists in the network and connects 235 * some other endpoint pair that is not equal to {@code endpoints} 236 * @throws IllegalArgumentException if the introduction of the edge would violate {@link 237 * #allowsParallelEdges()} or {@link #allowsSelfLoops()} 238 * @throws IllegalArgumentException if the endpoints are unordered and the network is directed 239 */ 240 @CanIgnoreReturnValue 241 public ImmutableNetwork.Builder<N, E> addEdge(EndpointPair<N> endpoints, E edge) { 242 mutableNetwork.addEdge(endpoints, edge); 243 return this; 244 } 245 246 /** 247 * Returns a newly-created {@code ImmutableNetwork} based on the contents of this {@code 248 * Builder}. 249 */ 250 public ImmutableNetwork<N, E> build() { 251 return ImmutableNetwork.copyOf(mutableNetwork); 252 } 253 } 254}