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/*
 * 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)}.
 *
 * 

See the Guava User's Guide's discussion * of the {@code Immutable*} types for more information on the properties and guarantees * provided by this class. * * @author James Sexton * @author Jens Nyman * @param Node parameter type * @param Value parameter type * @since 20.0 */ @Beta @Immutable(containerOf = {"N", "V"}) @SuppressWarnings("Immutable") // Extends StandardValueGraph but uses ImmutableMaps. public final class ImmutableValueGraph extends StandardValueGraph { private ImmutableValueGraph(ValueGraph graph) { super(ValueGraphBuilder.from(graph), getNodeConnections(graph), graph.edges().size()); } /** Returns an immutable copy of {@code graph}. */ public static ImmutableValueGraph copyOf(ValueGraph graph) { return (graph instanceof ImmutableValueGraph) ? (ImmutableValueGraph) graph : new ImmutableValueGraph(graph); } /** * Simply returns its argument. * * @deprecated no need to use this */ @Deprecated public static ImmutableValueGraph copyOf(ImmutableValueGraph graph) { return checkNotNull(graph); } @Override public ElementOrder incidentEdgeOrder() { return ElementOrder.stable(); } @Override public ImmutableGraph asGraph() { return new ImmutableGraph(this); // safe because the view is effectively immutable } private static ImmutableMap> getNodeConnections( ValueGraph 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> nodeConnections = ImmutableMap.builder(); for (N node : graph.nodes()) { nodeConnections.put(node, connectionsOf(graph, node)); } return nodeConnections.build(); } private static GraphConnections connectionsOf( final ValueGraph graph, final N node) { Function successorNodeToValueFn = new Function() { @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: * *

{@code
   * static final ImmutableValueGraph CITY_ROAD_DISTANCE_GRAPH =
   *     ValueGraphBuilder.undirected()
   *         .immutable()
   *         .putEdgeValue(PARIS, BERLIN, kilometers(1060))
   *         .putEdgeValue(PARIS, BRUSSELS, kilometers(317))
   *         .putEdgeValue(BERLIN, BRUSSELS, kilometers(764))
   *         .addNode(REYKJAVIK)
   *         .build();
   * }
* *

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 { private final MutableValueGraph mutableValueGraph; Builder(ValueGraphBuilder 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.stable()).build(); } /** * Adds {@code node} if it is not already present. * *

Nodes must be unique, just as {@code Map} keys must be. They must also be non-null. * * @return this {@code Builder} object */ @CanIgnoreReturnValue public ImmutableValueGraph.Builder 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). * *

If the graph is directed, the resultant edge will be directed; otherwise, it will be * undirected. * *

Values do not have to be unique. However, values must be non-null. * *

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 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). * *

If the graph is directed, the resultant edge will be directed; otherwise, it will be * undirected. * *

If this graph is directed, {@code endpoints} must be ordered. * *

Values do not have to be unique. However, values must be non-null. * *

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 putEdgeValue(EndpointPair 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 build() { return ImmutableValueGraph.copyOf(mutableValueGraph); } } }





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