001/* 002 * Copyright (C) 2016 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.checkArgument; 020import static com.google.common.base.Preconditions.checkNotNull; 021import static com.google.common.graph.Graphs.checkNonNegative; 022 023import com.google.common.annotations.Beta; 024import com.google.common.base.Optional; 025import com.google.errorprone.annotations.DoNotMock; 026 027/** 028 * A builder for constructing instances of {@link MutableGraph} or {@link ImmutableGraph} with 029 * user-defined properties. 030 * 031 * <p>A graph built by this class will have the following properties by default: 032 * 033 * <ul> 034 * <li>does not allow self-loops 035 * <li>orders {@link Graph#nodes()} in the order in which the elements were added 036 * </ul> 037 * 038 * <p>Examples of use: 039 * 040 * <pre>{@code 041 * // Building a mutable graph 042 * MutableGraph<String> graph = GraphBuilder.undirected().allowsSelfLoops(true).build(); 043 * graph.putEdge("bread", "bread"); 044 * graph.putEdge("chocolate", "peanut butter"); 045 * graph.putEdge("peanut butter", "jelly"); 046 * 047 * // Building an immutable graph 048 * ImmutableGraph<String> immutableGraph = 049 * GraphBuilder.undirected() 050 * .allowsSelfLoops(true) 051 * .<String>immutable() 052 * .putEdge("bread", "bread") 053 * .putEdge("chocolate", "peanut butter") 054 * .putEdge("peanut butter", "jelly") 055 * .build(); 056 * }</pre> 057 * 058 * @author James Sexton 059 * @author Joshua O'Madadhain 060 * @param <N> The most general node type this builder will support. This is normally {@code Object} 061 * unless it is constrained by using a method like {@link #nodeOrder}, or the builder is 062 * constructed based on an existing {@code Graph} using {@link #from(Graph)}. 063 * @since 20.0 064 */ 065@Beta 066@DoNotMock 067@ElementTypesAreNonnullByDefault 068public final class GraphBuilder<N> extends AbstractGraphBuilder<N> { 069 070 /** Creates a new instance with the specified edge directionality. */ 071 private GraphBuilder(boolean directed) { 072 super(directed); 073 } 074 075 /** Returns a {@link GraphBuilder} for building directed graphs. */ 076 public static GraphBuilder<Object> directed() { 077 return new GraphBuilder<>(true); 078 } 079 080 /** Returns a {@link GraphBuilder} for building undirected graphs. */ 081 public static GraphBuilder<Object> undirected() { 082 return new GraphBuilder<>(false); 083 } 084 085 /** 086 * Returns a {@link GraphBuilder} initialized with all properties queryable from {@code graph}. 087 * 088 * <p>The "queryable" properties are those that are exposed through the {@link Graph} interface, 089 * such as {@link Graph#isDirected()}. Other properties, such as {@link #expectedNodeCount(int)}, 090 * are not set in the new builder. 091 */ 092 public static <N> GraphBuilder<N> from(Graph<N> graph) { 093 return new GraphBuilder<N>(graph.isDirected()) 094 .allowsSelfLoops(graph.allowsSelfLoops()) 095 .nodeOrder(graph.nodeOrder()) 096 .incidentEdgeOrder(graph.incidentEdgeOrder()); 097 } 098 099 /** 100 * Returns an {@link ImmutableGraph.Builder} with the properties of this {@link GraphBuilder}. 101 * 102 * <p>The returned builder can be used for populating an {@link ImmutableGraph}. 103 * 104 * <p>Note that the returned builder will always have {@link #incidentEdgeOrder} set to {@link 105 * ElementOrder#stable()}, regardless of the value that was set in this builder. 106 * 107 * @since 28.0 108 */ 109 public <N1 extends N> ImmutableGraph.Builder<N1> immutable() { 110 GraphBuilder<N1> castBuilder = cast(); 111 return new ImmutableGraph.Builder<>(castBuilder); 112 } 113 114 /** 115 * Specifies whether the graph will allow self-loops (edges that connect a node to itself). 116 * Attempting to add a self-loop to a graph that does not allow them will throw an {@link 117 * UnsupportedOperationException}. 118 * 119 * <p>The default value is {@code false}. 120 */ 121 public GraphBuilder<N> allowsSelfLoops(boolean allowsSelfLoops) { 122 this.allowsSelfLoops = allowsSelfLoops; 123 return this; 124 } 125 126 /** 127 * Specifies the expected number of nodes in the graph. 128 * 129 * @throws IllegalArgumentException if {@code expectedNodeCount} is negative 130 */ 131 public GraphBuilder<N> expectedNodeCount(int expectedNodeCount) { 132 this.expectedNodeCount = Optional.of(checkNonNegative(expectedNodeCount)); 133 return this; 134 } 135 136 /** 137 * Specifies the order of iteration for the elements of {@link Graph#nodes()}. 138 * 139 * <p>The default value is {@link ElementOrder#insertion() insertion order}. 140 */ 141 public <N1 extends N> GraphBuilder<N1> nodeOrder(ElementOrder<N1> nodeOrder) { 142 GraphBuilder<N1> newBuilder = cast(); 143 newBuilder.nodeOrder = checkNotNull(nodeOrder); 144 return newBuilder; 145 } 146 147 /** 148 * Specifies the order of iteration for the elements of {@link Graph#edges()}, {@link 149 * Graph#adjacentNodes(Object)}, {@link Graph#predecessors(Object)}, {@link 150 * Graph#successors(Object)} and {@link Graph#incidentEdges(Object)}. 151 * 152 * <p>The default value is {@link ElementOrder#unordered() unordered} for mutable graphs. For 153 * immutable graphs, this value is ignored; they always have a {@link ElementOrder#stable() 154 * stable} order. 155 * 156 * @throws IllegalArgumentException if {@code incidentEdgeOrder} is not either {@code 157 * ElementOrder.unordered()} or {@code ElementOrder.stable()}. 158 * @since 29.0 159 */ 160 public <N1 extends N> GraphBuilder<N1> incidentEdgeOrder(ElementOrder<N1> incidentEdgeOrder) { 161 checkArgument( 162 incidentEdgeOrder.type() == ElementOrder.Type.UNORDERED 163 || incidentEdgeOrder.type() == ElementOrder.Type.STABLE, 164 "The given elementOrder (%s) is unsupported. incidentEdgeOrder() only supports" 165 + " ElementOrder.unordered() and ElementOrder.stable().", 166 incidentEdgeOrder); 167 GraphBuilder<N1> newBuilder = cast(); 168 newBuilder.incidentEdgeOrder = checkNotNull(incidentEdgeOrder); 169 return newBuilder; 170 } 171 172 /** Returns an empty {@link MutableGraph} with the properties of this {@link GraphBuilder}. */ 173 public <N1 extends N> MutableGraph<N1> build() { 174 return new StandardMutableGraph<>(this); 175 } 176 177 GraphBuilder<N> copy() { 178 GraphBuilder<N> newBuilder = new GraphBuilder<>(directed); 179 newBuilder.allowsSelfLoops = allowsSelfLoops; 180 newBuilder.nodeOrder = nodeOrder; 181 newBuilder.expectedNodeCount = expectedNodeCount; 182 newBuilder.incidentEdgeOrder = incidentEdgeOrder; 183 return newBuilder; 184 } 185 186 @SuppressWarnings("unchecked") 187 private <N1 extends N> GraphBuilder<N1> cast() { 188 return (GraphBuilder<N1>) this; 189 } 190}