| /* |
| * Copyright (C) 2016 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.collect.ImmutableMap; |
| import com.google.common.collect.Maps; |
| import com.google.errorprone.annotations.CanIgnoreReturnValue; |
| import com.google.errorprone.annotations.Immutable; |
| |
| /** |
| * A {@link ValueGraph} whose elements and structural relationships will never change. Instances of |
| * this class may be obtained with {@link #copyOf(ValueGraph)}. |
| * |
| * <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 Jens Nyman |
| * @param <N> Node parameter type |
| * @param <V> Value parameter type |
| * @since 20.0 |
| */ |
| @Beta |
| @Immutable(containerOf = {"N", "V"}) |
| @SuppressWarnings("Immutable") // Extends StandardValueGraph but uses ImmutableMaps. |
| public final class ImmutableValueGraph<N, V> extends StandardValueGraph<N, V> { |
| |
| private ImmutableValueGraph(ValueGraph<N, V> graph) { |
| super(ValueGraphBuilder.from(graph), getNodeConnections(graph), graph.edges().size()); |
| } |
| |
| /** Returns an immutable copy of {@code graph}. */ |
| public static <N, V> ImmutableValueGraph<N, V> copyOf(ValueGraph<N, V> graph) { |
| return (graph instanceof ImmutableValueGraph) |
| ? (ImmutableValueGraph<N, V>) graph |
| : new ImmutableValueGraph<N, V>(graph); |
| } |
| |
| /** |
| * Simply returns its argument. |
| * |
| * @deprecated no need to use this |
| */ |
| @Deprecated |
| public static <N, V> ImmutableValueGraph<N, V> copyOf(ImmutableValueGraph<N, V> graph) { |
| return checkNotNull(graph); |
| } |
| |
| @Override |
| public ElementOrder<N> incidentEdgeOrder() { |
| return ElementOrder.stable(); |
| } |
| |
| @Override |
| public ImmutableGraph<N> asGraph() { |
| return new ImmutableGraph<N>(this); // safe because the view is effectively immutable |
| } |
| |
| private static <N, V> ImmutableMap<N, GraphConnections<N, V>> getNodeConnections( |
| ValueGraph<N, V> 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, V>> nodeConnections = ImmutableMap.builder(); |
| for (N node : graph.nodes()) { |
| nodeConnections.put(node, connectionsOf(graph, node)); |
| } |
| return nodeConnections.build(); |
| } |
| |
| private static <N, V> GraphConnections<N, V> connectionsOf( |
| final ValueGraph<N, V> graph, final N node) { |
| Function<N, V> successorNodeToValueFn = |
| new Function<N, V>() { |
| @Override |
| public V apply(N successorNode) { |
| return graph.edgeValueOrDefault(node, successorNode, null); |
| } |
| }; |
| return graph.isDirected() |
| ? DirectedGraphConnections.ofImmutable( |
| node, graph.incidentEdges(node), successorNodeToValueFn) |
| : UndirectedGraphConnections.ofImmutable( |
| Maps.asMap(graph.adjacentNodes(node), successorNodeToValueFn)); |
| } |
| |
| /** |
| * A builder for creating {@link ImmutableValueGraph} instances, especially {@code static final} |
| * graphs. Example: |
| * |
| * <pre>{@code |
| * static final ImmutableValueGraph<City, Distance> CITY_ROAD_DISTANCE_GRAPH = |
| * ValueGraphBuilder.undirected() |
| * .<City, Distance>immutable() |
| * .putEdgeValue(PARIS, BERLIN, kilometers(1060)) |
| * .putEdgeValue(PARIS, BRUSSELS, kilometers(317)) |
| * .putEdgeValue(BERLIN, BRUSSELS, kilometers(764)) |
| * .addNode(REYKJAVIK) |
| * .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, V> { |
| |
| private final MutableValueGraph<N, V> mutableValueGraph; |
| |
| Builder(ValueGraphBuilder<N, V> 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.mutableValueGraph = |
| 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 ImmutableValueGraph.Builder<N, V> addNode(N node) { |
| mutableValueGraph.addNode(node); |
| return this; |
| } |
| |
| /** |
| * Adds an edge connecting {@code nodeU} to {@code nodeV} if one is not already present, and |
| * sets a value for that edge to {@code value} (overwriting the existing value, if any). |
| * |
| * <p>If the graph is directed, the resultant edge will be directed; otherwise, it will be |
| * undirected. |
| * |
| * <p>Values do not have to be unique. However, values must be non-null. |
| * |
| * <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 ImmutableValueGraph.Builder<N, V> putEdgeValue(N nodeU, N nodeV, V value) { |
| mutableValueGraph.putEdgeValue(nodeU, nodeV, value); |
| return this; |
| } |
| |
| /** |
| * Adds an edge connecting {@code endpoints} if one is not already present, and sets a value for |
| * that edge to {@code value} (overwriting the existing value, if any). |
| * |
| * <p>If the graph is directed, the resultant edge will be directed; otherwise, it will be |
| * undirected. |
| * |
| * <p>If this graph is directed, {@code endpoints} must be ordered. |
| * |
| * <p>Values do not have to be unique. However, values must be non-null. |
| * |
| * <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 ImmutableValueGraph.Builder<N, V> putEdgeValue(EndpointPair<N> endpoints, V value) { |
| mutableValueGraph.putEdgeValue(endpoints, value); |
| return this; |
| } |
| |
| /** |
| * Returns a newly-created {@code ImmutableValueGraph} based on the contents of this {@code |
| * Builder}. |
| */ |
| public ImmutableValueGraph<N, V> build() { |
| return ImmutableValueGraph.copyOf(mutableValueGraph); |
| } |
| } |
| } |