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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 com.google.common.annotations.Beta;
import java.util.Set;
import javax.annotation.Nullable;
/**
* An interface for graph-structured data,
* whose edges are anonymous entities with no identity or information of their own.
*
* A graph is composed of a set of nodes and a set of edges connecting pairs of nodes.
*
*
There are three primary interfaces provided to represent graphs. In order of increasing
* complexity they are: {@link Graph}, {@link ValueGraph}, and {@link Network}. You should generally
* prefer the simplest interface that satisfies your use case. See the
* "Choosing the right graph type" section of the Guava User Guide for more details.
*
*
Capabilities
*
* {@code Graph} supports the following use cases (definitions of
* terms):
*
*
* - directed graphs
*
- undirected graphs
*
- graphs that do/don't allow self-loops
*
- graphs whose nodes/edges are insertion-ordered, sorted, or unordered
*
*
* {@code Graph} explicitly does not support parallel edges, and forbids implementations or
* extensions with parallel edges. If you need parallel edges, use {@link Network}.
*
*
Building a {@code Graph}
*
* The implementation classes that {@code common.graph} provides are not public, by design. To
* create an instance of one of the built-in implementations of {@code Graph}, use the
* {@link GraphBuilder} class:
*
*
{@code
* MutableGraph graph = GraphBuilder.undirected().build();
* }
*
* {@link GraphBuilder#build()} returns an instance of {@link MutableGraph}, which is a subtype
* of {@code Graph} that provides methods for adding and removing nodes and edges. If you do not
* need to mutate a graph (e.g. if you write a method than runs a read-only algorithm on the graph),
* you should use the non-mutating {@link Graph} interface, or an {@link ImmutableGraph}.
*
*
You can create an immutable copy of an existing {@code Graph} using {@link
* ImmutableGraph#copyOf(Graph)}:
*
*
{@code
* ImmutableGraph immutableGraph = ImmutableGraph.copyOf(graph);
* }
*
* Instances of {@link ImmutableGraph} do not implement {@link MutableGraph} (obviously!) and are
* contractually guaranteed to be unmodifiable and thread-safe.
*
*
The Guava User Guide has more
* information on (and examples of) building graphs.
*
*
Additional documentation
*
* See the Guava User Guide for the {@code common.graph} package ("Graphs Explained") for
* additional documentation, including:
*
*
* -
* {@code equals()}, {@code hashCode()}, and graph equivalence
*
-
* Synchronization policy
*
- Notes
* for implementors
*
*
* @author James Sexton
* @author Joshua O'Madadhain
* @param Node parameter type
* @since 20.0
*/
@Beta
public interface Graph extends BaseGraph {
//
// Graph-level accessors
//
/** {@inheritDoc} */
@Override
Set nodes();
/** {@inheritDoc} */
@Override
Set> edges();
//
// Graph properties
//
/** {@inheritDoc} */
@Override
boolean isDirected();
/** {@inheritDoc} */
@Override
boolean allowsSelfLoops();
/** {@inheritDoc} */
@Override
ElementOrder nodeOrder();
//
// Element-level accessors
//
/** {@inheritDoc} */
@Override
Set adjacentNodes(N node);
/** {@inheritDoc} */
@Override
Set predecessors(N node);
/** {@inheritDoc} */
@Override
Set successors(N node);
/** {@inheritDoc} */
@Override
int degree(N node);
/** {@inheritDoc} */
@Override
int inDegree(N node);
/** {@inheritDoc} */
@Override
int outDegree(N node);
/** {@inheritDoc} */
@Override
boolean hasEdgeConnecting(N nodeU, N nodeV);
//
// Graph identity
//
/**
* Returns {@code true} iff {@code object} is a {@link Graph} that has the same elements and the
* same structural relationships as those in this graph.
*
* Thus, two graphs A and B are equal if all of the following are true:
*
*
* - A and B have equal {@link #isDirected() directedness}.
*
- A and B have equal {@link #nodes() node sets}.
*
- A and B have equal {@link #edges() edge sets}.
*
*
* Graph properties besides {@link #isDirected() directedness} do not affect equality.
* For example, two graphs may be considered equal even if one allows self-loops and the other
* doesn't. Additionally, the order in which nodes or edges are added to the graph, and the order
* in which they are iterated over, are irrelevant.
*
*
A reference implementation of this is provided by {@link AbstractGraph#equals(Object)}.
*/
@Override
boolean equals(@Nullable Object object);
/**
* Returns the hash code for this graph. The hash code of a graph is defined as the hash code of
* the set returned by {@link #edges()}.
*
*
A reference implementation of this is provided by {@link AbstractGraph#hashCode()}.
*/
@Override
int hashCode();
}