org.jgrapht.GraphIterables Maven / Gradle / Ivy
/*
* (C) Copyright 2020-2021, by Dimitrios Michail and Contributors.
*
* JGraphT : a free Java graph-theory library
*
* See the CONTRIBUTORS.md file distributed with this work for additional
* information regarding copyright ownership.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0, or the
* GNU Lesser General Public License v2.1 or later
* which is available at
* http://www.gnu.org/licenses/old-licenses/lgpl-2.1-standalone.html.
*
* SPDX-License-Identifier: EPL-2.0 OR LGPL-2.1-or-later
*/
package org.jgrapht;
import org.jgrapht.util.LiveIterableWrapper;
/**
* Presents a graph as a collection of views suitable for graphs which contain a very large number
* of vertices or edges. Graph algorithms written these methods can work with graphs without the
* restrictions imposed by 32-bit arithmetic.
*
*
* Whether the returned iterators support removal of elements is left to the graph implementation.
* It is the responsibility of callers who rely on this behavior to only use graph implementations
* which support it.
*
*
* @param the graph vertex type
* @param the graph edge type
*
* @author Dimitrios Michail
*/
public interface GraphIterables
{
/**
* Get the underlying graph.
*
* @return the underlying graph
*/
Graph getGraph();
/**
* Returns an iterable over the edges of the graph.
*
*
* Whether the ordering is deterministic, depends on the actual graph implementation. It is the
* responsibility of callers who rely on this behavior to only use graph implementations which
* support it.
*
* @return an iterable over the edges of the graph.
*/
default Iterable edges()
{
return new LiveIterableWrapper<>(() -> getGraph().edgeSet());
}
/**
* Return the number of edges in the graph.
*
* @return the number of edges.
*/
default long edgeCount()
{
return getGraph().edgeSet().size();
}
/**
* Returns an iterable view over the vertices contained in this graph. The returned iterator is
* a live view of the vertices. If the graph is modified while an iteration is in progress, the
* results of the iteration are undefined.
*
*
* The graph implementation may maintain a particular ordering for deterministic iteration, but
* this is not required. It is the responsibility of callers who rely on this behavior to only
* use graph implementations which support it.
*
*
* @return an iterable view of the vertices contained in this graph
*/
default Iterable vertices()
{
return new LiveIterableWrapper<>(() -> getGraph().vertexSet());
}
/**
* Return the number of vertices in the graph.
*
* @return the number of vertices
*/
default long vertexCount()
{
return getGraph().vertexSet().size();
}
/**
* Returns an iterable view over all edges touching the specified vertex. The returned iterators
* are live views. If the graph is modified while an iteration is in progress, the results of
* the iteration are undefined. If no edges are touching the specified vertex, the returned
* iterators are already exhausted.
*
* @param vertex input vertex
* @return an iterable view of the vertices contained in this graph
* @throws IllegalArgumentException if vertex is not found in the graph.
* @throws NullPointerException if vertex is null.
*/
default Iterable edgesOf(V vertex)
{
return new LiveIterableWrapper<>(() -> getGraph().edgesOf(vertex));
}
/**
* Returns the degree of the specified vertex.
*
*
* A degree of a vertex in an undirected graph is the number of edges touching that vertex.
* Edges with same source and target vertices (self-loops) are counted twice.
*
*
* In directed graphs this method returns the sum of the "in degree" and the "out degree".
*
* @param vertex vertex whose degree is to be calculated.
* @return the degree of the specified vertex.
*
* @throws IllegalArgumentException if vertex is not found in the graph.
* @throws NullPointerException if vertex is null.
*/
default long degreeOf(V vertex)
{
return getGraph().degreeOf(vertex);
}
/**
* Returns an iterable view over all edges incoming into the specified vertex. The returned
* iterators are live views. If the graph is modified while an iteration is in progress, the
* results of the iteration are undefined.
*
*
* In the case of undirected graphs the returned iterators return all edges touching the vertex,
* thus, some of the returned edges may have their source and target vertices in the opposite
* order.
*
* @param vertex input vertex
* @return an iterable view of all edges incoming into the specified vertex
* @throws IllegalArgumentException if vertex is not found in the graph.
* @throws NullPointerException if vertex is null.
*/
default Iterable incomingEdgesOf(V vertex)
{
return new LiveIterableWrapper<>(() -> getGraph().incomingEdgesOf(vertex));
}
/**
* Returns the "in degree" of the specified vertex.
*
*
* The "in degree" of a vertex in a directed graph is the number of inward directed edges from
* that vertex. See
* http://mathworld.wolfram.com/Indegree.html.
*
*
* In the case of undirected graphs this method returns the number of edges touching the vertex.
* Edges with same source and target vertices (self-loops) are counted twice.
*
* @param vertex vertex whose degree is to be calculated.
* @return the degree of the specified vertex.
*
* @throws IllegalArgumentException if vertex is not found in the graph.
* @throws NullPointerException if vertex is null.
*/
default long inDegreeOf(V vertex)
{
return getGraph().inDegreeOf(vertex);
}
/**
* Returns an iterable view over all edges outgoing into the specified vertex. The returned
* iterators are live views. If the graph is modified while an iteration is in progress, the
* results of the iteration are undefined.
*
*
* In the case of undirected graphs the returned iterators return all edges touching the vertex,
* thus, some of the returned edges may have their source and target vertices in the opposite
* order.
*
* @param vertex input vertex
* @return an iterable view of all edges outgoing from the specified vertex
* @throws IllegalArgumentException if vertex is not found in the graph.
* @throws NullPointerException if vertex is null.
*/
default Iterable outgoingEdgesOf(V vertex)
{
return new LiveIterableWrapper<>(() -> getGraph().outgoingEdgesOf(vertex));
}
/**
* Returns the "out degree" of the specified vertex.
*
*
* The "out degree" of a vertex in a directed graph is the number of outward directed edges from
* that vertex. See
* http://mathworld.wolfram.com/Outdegree.html.
*
*
* In the case of undirected graphs this method returns the number of edges touching the vertex.
* Edges with same source and target vertices (self-loops) are counted twice.
*
* @param vertex vertex whose degree is to be calculated.
* @return the degree of the specified vertex.
*
* @throws IllegalArgumentException if vertex is not found in the graph.
* @throws NullPointerException if vertex is null.
*/
default long outDegreeOf(V vertex)
{
return getGraph().outDegreeOf(vertex);
}
/**
* Returns an iterable view over all edges connecting source vertex to target vertex if such
* vertices exist in this graph. The returned iterators are live views. If the graph is modified
* while an iteration is in progress, the results of the iteration are undefined.
*
* If any of the vertices does not exist or is null, returns null. If
* both vertices exist but no edges found, returns an iterable which returns exhausted
* iterators.
*
*
* In undirected graphs, some of the returned edges may have their source and target vertices in
* the opposite order. In simple graphs the returned set is either singleton set or empty set.
*
*
* @param sourceVertex source vertex of the edge.
* @param targetVertex target vertex of the edge.
*
* @return an iterable view of all edges connecting source to target vertex.
*
* @throws IllegalArgumentException if vertex is not found in the graph.
* @throws NullPointerException if vertex is null.
*/
default Iterable allEdges(V sourceVertex, V targetVertex)
{
return new LiveIterableWrapper<>(() -> getGraph().getAllEdges(sourceVertex, targetVertex));
}
}