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/*
 * 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)}.
 *
 * 

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 Joshua O'Madadhain * @author Omar Darwish * @author Jens Nyman * @param Node parameter type * @since 20.0 */ @Beta @Immutable(containerOf = {"N"}) @ElementTypesAreNonnullByDefault public class ImmutableGraph extends ForwardingGraph { @SuppressWarnings("Immutable") // The backing graph must be immutable. private final BaseGraph backingGraph; ImmutableGraph(BaseGraph backingGraph) { this.backingGraph = backingGraph; } /** Returns an immutable copy of {@code graph}. */ public static ImmutableGraph copyOf(Graph graph) { return (graph instanceof ImmutableGraph) ? (ImmutableGraph) graph : new ImmutableGraph( new StandardValueGraph( GraphBuilder.from(graph), getNodeConnections(graph), graph.edges().size())); } /** * Simply returns its argument. * * @deprecated no need to use this */ @Deprecated public static ImmutableGraph copyOf(ImmutableGraph graph) { return checkNotNull(graph); } @Override public ElementOrder incidentEdgeOrder() { return ElementOrder.stable(); } private static ImmutableMap> getNodeConnections( Graph 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.buildOrThrow(); } @SuppressWarnings("unchecked") private static GraphConnections connectionsOf(Graph graph, N node) { Function edgeValueFn = (Function) Functions.constant(Presence.EDGE_EXISTS); return graph.isDirected() ? DirectedGraphConnections.ofImmutable(node, graph.incidentEdges(node), edgeValueFn) : UndirectedGraphConnections.ofImmutable( Maps.asMap(graph.adjacentNodes(node), edgeValueFn)); } @Override BaseGraph delegate() { return backingGraph; } /** * A builder for creating {@link ImmutableGraph} instances, especially {@code static final} * graphs. Example: * *

{@code
   * static final ImmutableGraph COUNTRY_ADJACENCY_GRAPH =
   *     GraphBuilder.undirected()
   *         .immutable()
   *         .putEdge(FRANCE, GERMANY)
   *         .putEdge(FRANCE, BELGIUM)
   *         .putEdge(GERMANY, BELGIUM)
   *         .addNode(ICELAND)
   *         .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 MutableGraph mutableGraph; Builder(GraphBuilder 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.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 Builder addNode(N node) { mutableGraph.addNode(node); return this; } /** * Adds an edge connecting {@code nodeU} to {@code nodeV} if one is not already present. * *

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

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 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. * *

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. * *

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

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 putEdge(EndpointPair endpoints) { mutableGraph.putEdge(endpoints); return this; } /** * Returns a newly-created {@code ImmutableGraph} based on the contents of this {@code Builder}. */ public ImmutableGraph build() { return ImmutableGraph.copyOf(mutableGraph); } } }





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