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.checkNotNull;
020import static com.google.common.graph.Graphs.checkNonNegative;
021
022import com.google.common.annotations.Beta;
023import com.google.common.base.Optional;
024
025/**
026 * A builder for constructing instances of {@link MutableValueGraph} with user-defined properties.
027 *
028 * <p>A graph built by this class will have the following properties by default:
029 *
030 * <ul>
031 *   <li>does not allow self-loops
032 *   <li>orders {@link Graph#nodes()} in the order in which the elements were added
033 * </ul>
034 *
035 * <p>Example of use:
036 *
037 * <pre>{@code
038 * MutableValueGraph<String, Double> graph =
039 *     ValueGraphBuilder.undirected().allowsSelfLoops(true).build();
040 * graph.putEdgeValue("San Francisco", "San Francisco", 0.0);
041 * graph.putEdgeValue("San Jose", "San Jose", 0.0);
042 * graph.putEdgeValue("San Francisco", "San Jose", 48.4);
043 * }</pre>
044 *
045 * @author James Sexton
046 * @author Joshua O'Madadhain
047 * @since 20.0
048 */
049@Beta
050public final class ValueGraphBuilder<N, V> extends AbstractGraphBuilder<N> {
051
052  /** Creates a new instance with the specified edge directionality. */
053  private ValueGraphBuilder(boolean directed) {
054    super(directed);
055  }
056
057  /** Returns a {@link ValueGraphBuilder} for building directed graphs. */
058  public static ValueGraphBuilder<Object, Object> directed() {
059    return new ValueGraphBuilder<>(true);
060  }
061
062  /** Returns a {@link ValueGraphBuilder} for building undirected graphs. */
063  public static ValueGraphBuilder<Object, Object> undirected() {
064    return new ValueGraphBuilder<>(false);
065  }
066
067  /**
068   * Returns a {@link ValueGraphBuilder} initialized with all properties queryable from {@code
069   * graph}.
070   *
071   * <p>The "queryable" properties are those that are exposed through the {@link ValueGraph}
072   * interface, such as {@link ValueGraph#isDirected()}. Other properties, such as {@link
073   * #expectedNodeCount(int)}, are not set in the new builder.
074   */
075  public static <N, V> ValueGraphBuilder<N, V> from(ValueGraph<N, V> graph) {
076    return new ValueGraphBuilder<N, V>(graph.isDirected())
077        .allowsSelfLoops(graph.allowsSelfLoops())
078        .nodeOrder(graph.nodeOrder());
079  }
080
081  /**
082   * Specifies whether the graph will allow self-loops (edges that connect a node to itself).
083   * Attempting to add a self-loop to a graph that does not allow them will throw an {@link
084   * UnsupportedOperationException}.
085   */
086  public ValueGraphBuilder<N, V> allowsSelfLoops(boolean allowsSelfLoops) {
087    this.allowsSelfLoops = allowsSelfLoops;
088    return this;
089  }
090
091  /**
092   * Specifies the expected number of nodes in the graph.
093   *
094   * @throws IllegalArgumentException if {@code expectedNodeCount} is negative
095   */
096  public ValueGraphBuilder<N, V> expectedNodeCount(int expectedNodeCount) {
097    this.expectedNodeCount = Optional.of(checkNonNegative(expectedNodeCount));
098    return this;
099  }
100
101  /** Specifies the order of iteration for the elements of {@link Graph#nodes()}. */
102  public <N1 extends N> ValueGraphBuilder<N1, V> nodeOrder(ElementOrder<N1> nodeOrder) {
103    ValueGraphBuilder<N1, V> newBuilder = cast();
104    newBuilder.nodeOrder = checkNotNull(nodeOrder);
105    return newBuilder;
106  }
107
108  /**
109   * Returns an empty {@link MutableValueGraph} with the properties of this {@link
110   * ValueGraphBuilder}.
111   */
112  public <N1 extends N, V1 extends V> MutableValueGraph<N1, V1> build() {
113    return new ConfigurableMutableValueGraph<>(this);
114  }
115
116  @SuppressWarnings("unchecked")
117  private <N1 extends N, V1 extends V> ValueGraphBuilder<N1, V1> cast() {
118    return (ValueGraphBuilder<N1, V1>) this;
119  }
120}