| /* |
| * Copyright (C) 2014 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 static com.google.common.base.Preconditions.checkNotNull; |
| |
| import com.google.common.annotations.Beta; |
| import com.google.common.base.Function; |
| import com.google.common.base.Functions; |
| import com.google.common.collect.ImmutableMap; |
| import com.google.common.collect.Maps; |
| import com.google.common.graph.GraphConstants.Presence; |
| import com.google.errorprone.annotations.CanIgnoreReturnValue; |
| import com.google.errorprone.annotations.Immutable; |
| |
| /** |
| * A {@link Graph} whose elements and structural relationships will never change. Instances of this |
| * class may be obtained with {@link #copyOf(Graph)}. |
| * |
| * <p>See the Guava User's Guide's <a |
| * href="https://github.com/google/guava/wiki/GraphsExplained#immutable-implementations">discussion |
| * of the {@code Immutable*} types</a> for more information on the properties and guarantees |
| * provided by this class. |
| * |
| * @author James Sexton |
| * @author Joshua O'Madadhain |
| * @author Omar Darwish |
| * @author Jens Nyman |
| * @param <N> Node parameter type |
| * @since 20.0 |
| */ |
| @Beta |
| @Immutable(containerOf = {"N"}) |
| public class ImmutableGraph<N> extends ForwardingGraph<N> { |
| @SuppressWarnings("Immutable") // The backing graph must be immutable. |
| private final BaseGraph<N> backingGraph; |
| |
| ImmutableGraph(BaseGraph<N> backingGraph) { |
| this.backingGraph = backingGraph; |
| } |
| |
| /** Returns an immutable copy of {@code graph}. */ |
| public static <N> ImmutableGraph<N> copyOf(Graph<N> graph) { |
| return (graph instanceof ImmutableGraph) |
| ? (ImmutableGraph<N>) graph |
| : new ImmutableGraph<N>( |
| new StandardValueGraph<N, Presence>( |
| GraphBuilder.from(graph), getNodeConnections(graph), graph.edges().size())); |
| } |
| |
| /** |
| * Simply returns its argument. |
| * |
| * @deprecated no need to use this |
| */ |
| @Deprecated |
| public static <N> ImmutableGraph<N> copyOf(ImmutableGraph<N> graph) { |
| return checkNotNull(graph); |
| } |
| |
| @Override |
| public ElementOrder<N> incidentEdgeOrder() { |
| return ElementOrder.stable(); |
| } |
| |
| private static <N> ImmutableMap<N, GraphConnections<N, Presence>> getNodeConnections( |
| Graph<N> graph) { |
| // ImmutableMap.Builder maintains the order of the elements as inserted, so the map will have |
| // whatever ordering the graph's nodes do, so ImmutableSortedMap is unnecessary even if the |
| // input nodes are sorted. |
| ImmutableMap.Builder<N, GraphConnections<N, Presence>> nodeConnections = ImmutableMap.builder(); |
| for (N node : graph.nodes()) { |
| nodeConnections.put(node, connectionsOf(graph, node)); |
| } |
| return nodeConnections.build(); |
| } |
| |
| @SuppressWarnings("unchecked") |
| private static <N> GraphConnections<N, Presence> connectionsOf(Graph<N> graph, N node) { |
| Function<N, Presence> edgeValueFn = |
| (Function<N, Presence>) Functions.constant(Presence.EDGE_EXISTS); |
| return graph.isDirected() |
| ? DirectedGraphConnections.ofImmutable(node, graph.incidentEdges(node), edgeValueFn) |
| : UndirectedGraphConnections.ofImmutable( |
| Maps.asMap(graph.adjacentNodes(node), edgeValueFn)); |
| } |
| |
| @Override |
| protected BaseGraph<N> delegate() { |
| return backingGraph; |
| } |
| |
| /** |
| * A builder for creating {@link ImmutableGraph} instances, especially {@code static final} |
| * graphs. Example: |
| * |
| * <pre>{@code |
| * static final ImmutableGraph<Country> COUNTRY_ADJACENCY_GRAPH = |
| * GraphBuilder.undirected() |
| * .<Country>immutable() |
| * .putEdge(FRANCE, GERMANY) |
| * .putEdge(FRANCE, BELGIUM) |
| * .putEdge(GERMANY, BELGIUM) |
| * .addNode(ICELAND) |
| * .build(); |
| * }</pre> |
| * |
| * <p>Builder instances can be reused; it is safe to call {@link #build} multiple times to build |
| * multiple graphs in series. Each new graph contains all the elements of the ones created before |
| * it. |
| * |
| * @since 28.0 |
| */ |
| public static class Builder<N> { |
| |
| private final MutableGraph<N> mutableGraph; |
| |
| Builder(GraphBuilder<N> graphBuilder) { |
| // The incidentEdgeOrder for immutable graphs is always stable. However, we don't want to |
| // modify this builder, so we make a copy instead. |
| this.mutableGraph = graphBuilder.copy().incidentEdgeOrder(ElementOrder.<N>stable()).build(); |
| } |
| |
| /** |
| * Adds {@code node} if it is not already present. |
| * |
| * <p><b>Nodes must be unique</b>, just as {@code Map} keys must be. They must also be non-null. |
| * |
| * @return this {@code Builder} object |
| */ |
| @CanIgnoreReturnValue |
| public Builder<N> addNode(N node) { |
| mutableGraph.addNode(node); |
| return this; |
| } |
| |
| /** |
| * Adds an edge connecting {@code nodeU} to {@code nodeV} if one is not already present. |
| * |
| * <p>If the graph is directed, the resultant edge will be directed; otherwise, it will be |
| * undirected. |
| * |
| * <p>If {@code nodeU} and {@code nodeV} are not already present in this graph, this method will |
| * silently {@link #addNode(Object) add} {@code nodeU} and {@code nodeV} to the graph. |
| * |
| * @return this {@code Builder} object |
| * @throws IllegalArgumentException if the introduction of the edge would violate {@link |
| * #allowsSelfLoops()} |
| */ |
| @CanIgnoreReturnValue |
| public Builder<N> putEdge(N nodeU, N nodeV) { |
| mutableGraph.putEdge(nodeU, nodeV); |
| return this; |
| } |
| |
| /** |
| * Adds an edge connecting {@code endpoints} (in the order, if any, specified by {@code |
| * endpoints}) if one is not already present. |
| * |
| * <p>If this graph is directed, {@code endpoints} must be ordered and the added edge will be |
| * directed; if it is undirected, the added edge will be undirected. |
| * |
| * <p>If this graph is directed, {@code endpoints} must be ordered. |
| * |
| * <p>If either or both endpoints are not already present in this graph, this method will |
| * silently {@link #addNode(Object) add} each missing endpoint to the graph. |
| * |
| * @return this {@code Builder} object |
| * @throws IllegalArgumentException if the introduction of the edge would violate {@link |
| * #allowsSelfLoops()} |
| * @throws IllegalArgumentException if the endpoints are unordered and the graph is directed |
| */ |
| @CanIgnoreReturnValue |
| public Builder<N> putEdge(EndpointPair<N> endpoints) { |
| mutableGraph.putEdge(endpoints); |
| return this; |
| } |
| |
| /** |
| * Returns a newly-created {@code ImmutableGraph} based on the contents of this {@code Builder}. |
| */ |
| public ImmutableGraph<N> build() { |
| return ImmutableGraph.copyOf(mutableGraph); |
| } |
| } |
| } |