1 /*
2 * Copyright (C) 2016 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 package com.google.common.graph;
18
19 import static com.google.common.base.Preconditions.checkArgument;
20 import static com.google.common.base.Preconditions.checkNotNull;
21 import static com.google.common.graph.Graphs.checkNonNegative;
22
23 import com.google.common.annotations.Beta;
24 import com.google.common.base.Optional;
25 import com.google.errorprone.annotations.DoNotMock;
26
27 /**
28 * A builder for constructing instances of {@link MutableGraph} or {@link ImmutableGraph} with
29 * user-defined properties.
30 *
31 * <p>A graph built by this class will have the following properties by default:
32 *
33 * <ul>
34 * <li>does not allow self-loops
35 * <li>orders {@link Graph#nodes()} in the order in which the elements were added
36 * </ul>
37 *
38 * <p>Examples of use:
39 *
40 * <pre>{@code
41 * // Building a mutable graph
42 * MutableGraph<String> graph = GraphBuilder.undirected().allowsSelfLoops(true).build();
43 * graph.putEdge("bread", "bread");
44 * graph.putEdge("chocolate", "peanut butter");
45 * graph.putEdge("peanut butter", "jelly");
46 *
47 * // Building an immutable graph
48 * ImmutableGraph<String> immutableGraph =
49 * GraphBuilder.undirected()
50 * .allowsSelfLoops(true)
51 * .<String>immutable()
52 * .putEdge("bread", "bread")
53 * .putEdge("chocolate", "peanut butter")
54 * .putEdge("peanut butter", "jelly")
55 * .build();
56 * }</pre>
57 *
58 * @author James Sexton
59 * @author Joshua O'Madadhain
60 * @param <N> The most general node type this builder will support. This is normally {@code Object}
61 * unless it is constrained by using a method like {@link #nodeOrder}, or the builder is
62 * constructed based on an existing {@code Graph} using {@link #from(Graph)}.
63 * @since 20.0
64 */
65 @Beta
66 @DoNotMock
67 @ElementTypesAreNonnullByDefault
68 public final class GraphBuilder<N> extends AbstractGraphBuilder<N> {
69
70 /** Creates a new instance with the specified edge directionality. */
71 private GraphBuilder(boolean directed) {
72 super(directed);
73 }
74
75 /** Returns a {@link GraphBuilder} for building directed graphs. */
76 public static GraphBuilder<Object> directed() {
77 return new GraphBuilder<>(true);
78 }
79
80 /** Returns a {@link GraphBuilder} for building undirected graphs. */
81 public static GraphBuilder<Object> undirected() {
82 return new GraphBuilder<>(false);
83 }
84
85 /**
86 * Returns a {@link GraphBuilder} initialized with all properties queryable from {@code graph}.
87 *
88 * <p>The "queryable" properties are those that are exposed through the {@link Graph} interface,
89 * such as {@link Graph#isDirected()}. Other properties, such as {@link #expectedNodeCount(int)},
90 * are not set in the new builder.
91 */
92 public static <N> GraphBuilder<N> from(Graph<N> graph) {
93 return new GraphBuilder<N>(graph.isDirected())
94 .allowsSelfLoops(graph.allowsSelfLoops())
95 .nodeOrder(graph.nodeOrder())
96 .incidentEdgeOrder(graph.incidentEdgeOrder());
97 }
98
99 /**
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<N1>(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 }