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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.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.graph.Graphs.checkNonNegative;
import com.google.common.annotations.Beta;
import com.google.common.base.Optional;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.DoNotMock;
/**
* A builder for constructing instances of {@link MutableGraph} or {@link ImmutableGraph} with
* user-defined properties.
*
* <p>A {@code Graph} built by this class has the following default properties:
*
* <ul>
* <li>does not allow self-loops
* <li>orders {@link Graph#nodes()} in the order in which the elements were added (insertion
* order)
* </ul>
*
* <p>{@code Graph}s built by this class also guarantee that each collection-returning accessor
* returns a <b>(live) unmodifiable view</b>; see <a
* href="https://github.com/google/guava/wiki/GraphsExplained#accessor-behavior">the external
* documentation</a> for details.
*
* <p>Examples of use:
*
* <pre>{@code
* // Building a mutable graph
* MutableGraph<String> graph = GraphBuilder.undirected().allowsSelfLoops(true).build();
* graph.putEdge("bread", "bread");
* graph.putEdge("chocolate", "peanut butter");
* graph.putEdge("peanut butter", "jelly");
*
* // Building an immutable graph
* ImmutableGraph<String> immutableGraph =
* GraphBuilder.undirected()
* .allowsSelfLoops(true)
* .<String>immutable()
* .putEdge("bread", "bread")
* .putEdge("chocolate", "peanut butter")
* .putEdge("peanut butter", "jelly")
* .build();
* }</pre>
*
* @author James Sexton
* @author Joshua O'Madadhain
* @param <N> The most general node type this builder will support. This is normally {@code Object}
* unless it is constrained by using a method like {@link #nodeOrder}, or the builder is
* constructed based on an existing {@code Graph} using {@link #from(Graph)}.
* @since 20.0
*/
@Beta
@DoNotMock
@ElementTypesAreNonnullByDefault
public final class GraphBuilder<N> extends AbstractGraphBuilder<N> {
/** Creates a new instance with the specified edge directionality. */
private GraphBuilder(boolean directed) {
super(directed);
}
/** Returns a {@link GraphBuilder} for building directed graphs. */
public static GraphBuilder<Object> directed() {
return new GraphBuilder<>(true);
}
/** Returns a {@link GraphBuilder} for building undirected graphs. */
public static GraphBuilder<Object> undirected() {
return new GraphBuilder<>(false);
}
/**
* Returns a {@link GraphBuilder} initialized with all properties queryable from {@code graph}.
*
* <p>The "queryable" properties are those that are exposed through the {@link Graph} interface,
* such as {@link Graph#isDirected()}. Other properties, such as {@link #expectedNodeCount(int)},
* are not set in the new builder.
*/
public static <N> GraphBuilder<N> from(Graph<N> graph) {
return new GraphBuilder<N>(graph.isDirected())
.allowsSelfLoops(graph.allowsSelfLoops())
.nodeOrder(graph.nodeOrder())
.incidentEdgeOrder(graph.incidentEdgeOrder());
}
/**
* Returns an {@link ImmutableGraph.Builder} with the properties of this {@link GraphBuilder}.
*
* <p>The returned builder can be used for populating an {@link ImmutableGraph}.
*
* <p>Note that the returned builder will always have {@link #incidentEdgeOrder} set to {@link
* ElementOrder#stable()}, regardless of the value that was set in this builder.
*
* @since 28.0
*/
public <N1 extends N> ImmutableGraph.Builder<N1> immutable() {
GraphBuilder<N1> castBuilder = cast();
return new ImmutableGraph.Builder<>(castBuilder);
}
/**
* Specifies whether the graph will allow self-loops (edges that connect a node to itself).
* Attempting to add a self-loop to a graph that does not allow them will throw an {@link
* UnsupportedOperationException}.
*
* <p>The default value is {@code false}.
*/
@CanIgnoreReturnValue
public GraphBuilder<N> allowsSelfLoops(boolean allowsSelfLoops) {
this.allowsSelfLoops = allowsSelfLoops;
return this;
}
/**
* Specifies the expected number of nodes in the graph.
*
* @throws IllegalArgumentException if {@code expectedNodeCount} is negative
*/
@CanIgnoreReturnValue
public GraphBuilder<N> expectedNodeCount(int expectedNodeCount) {
this.expectedNodeCount = Optional.of(checkNonNegative(expectedNodeCount));
return this;
}
/**
* Specifies the order of iteration for the elements of {@link Graph#nodes()}.
*
* <p>The default value is {@link ElementOrder#insertion() insertion order}.
*/
public <N1 extends N> GraphBuilder<N1> nodeOrder(ElementOrder<N1> nodeOrder) {
GraphBuilder<N1> newBuilder = cast();
newBuilder.nodeOrder = checkNotNull(nodeOrder);
return newBuilder;
}
/**
* Specifies the order of iteration for the elements of {@link Graph#edges()}, {@link
* Graph#adjacentNodes(Object)}, {@link Graph#predecessors(Object)}, {@link
* Graph#successors(Object)} and {@link Graph#incidentEdges(Object)}.
*
* <p>The default value is {@link ElementOrder#unordered() unordered} for mutable graphs. For
* immutable graphs, this value is ignored; they always have a {@link ElementOrder#stable()
* stable} order.
*
* @throws IllegalArgumentException if {@code incidentEdgeOrder} is not either {@code
* ElementOrder.unordered()} or {@code ElementOrder.stable()}.
* @since 29.0
*/
public <N1 extends N> GraphBuilder<N1> incidentEdgeOrder(ElementOrder<N1> incidentEdgeOrder) {
checkArgument(
incidentEdgeOrder.type() == ElementOrder.Type.UNORDERED
|| incidentEdgeOrder.type() == ElementOrder.Type.STABLE,
"The given elementOrder (%s) is unsupported. incidentEdgeOrder() only supports"
+ " ElementOrder.unordered() and ElementOrder.stable().",
incidentEdgeOrder);
GraphBuilder<N1> newBuilder = cast();
newBuilder.incidentEdgeOrder = checkNotNull(incidentEdgeOrder);
return newBuilder;
}
/** Returns an empty {@link MutableGraph} with the properties of this {@link GraphBuilder}. */
public <N1 extends N> MutableGraph<N1> build() {
return new StandardMutableGraph<>(this);
}
GraphBuilder<N> copy() {
GraphBuilder<N> newBuilder = new GraphBuilder<>(directed);
newBuilder.allowsSelfLoops = allowsSelfLoops;
newBuilder.nodeOrder = nodeOrder;
newBuilder.expectedNodeCount = expectedNodeCount;
newBuilder.incidentEdgeOrder = incidentEdgeOrder;
return newBuilder;
}
@SuppressWarnings("unchecked")
private <N1 extends N> GraphBuilder<N1> cast() {
return (GraphBuilder<N1>) this;
}
}
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