org.jgrapht.alg.connectivity

Class ConnectivityInspector<V,E>

java.lang.Object

org.jgrapht.alg.connectivity.ConnectivityInspector<V,E>

Type Parameters:

V - the graph vertex type

E - the graph edge type

All Implemented Interfaces:

EventListener, GraphListener<V,E>, VertexSetListener<V>

public class ConnectivityInspector<V,E>
extends Object
implements GraphListener<V,E>

Allows obtaining various connectivity aspects of a graph. The inspected graph is specified at construction time and cannot be modified. Currently, the inspector supports connected components for an undirected graph and weakly connected components for a directed graph. To find strongly connected components, use KosarajuStrongConnectivityInspector instead.

The inspector methods work in a lazy fashion: no computation is performed unless immediately necessary. Computation are done once and results and cached within this class for future need.

The inspector is also a GraphListener. If added as a listener to the inspected graph, the inspector will amend internal cached results instead of recomputing them. It is efficient when a few modifications are applied to a large graph. If many modifications are expected it will not be efficient due to added overhead on graph update operations. If inspector is added as listener to a graph other than the one it inspects, results are undefined.

Author:

Barak Naveh, John V. Sichi

Constructor Summary

Constructors

Constructor and Description
ConnectivityInspector(Graph<V,E> g) Creates a connectivity inspector for the specified graph.

Method Summary

Modifier and Type	Method and Description
Set<V>	connectedSetOf(V vertex) Returns a set of all vertices that are in the maximally connected component together with the specified vertex.
List<Set<V>>	connectedSets() Returns a list of Set s, where each set contains all vertices that are in the same maximally connected component.
void	edgeAdded(GraphEdgeChangeEvent<V,E> e) Notifies that an edge has been added to the graph.
void	edgeRemoved(GraphEdgeChangeEvent<V,E> e) Notifies that an edge has been removed from the graph.
boolean	isConnected() Test if the inspected graph is connected.
boolean	pathExists(V sourceVertex, V targetVertex) Tests whether two vertices lay respectively in the same connected component (undirected graph), or in the same weakly connected component (directed graph).
void	vertexAdded(GraphVertexChangeEvent<V> e) Notifies that a vertex has been added to the graph.
void	vertexRemoved(GraphVertexChangeEvent<V> e) Notifies that a vertex has been removed from the graph.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.jgrapht.event.GraphListener

edgeWeightUpdated

Constructor Detail

ConnectivityInspector

public ConnectivityInspector(Graph<V,E> g)

Creates a connectivity inspector for the specified graph.

Parameters:

g - the graph for which a connectivity inspector to be created.

Method Detail

isConnected

public boolean isConnected()

Test if the inspected graph is connected. A graph is connected when there is a path between every pair of vertices. In a connected graph, there are no unreachable vertices. When the inspected graph is a directed graph, this method returns true if and only if the inspected graph is weakly connected. An empty graph is not considered connected.

Returns:

true if and only if inspected graph is connected.

connectedSetOf

public Set<V> connectedSetOf(V vertex)

Returns a set of all vertices that are in the maximally connected component together with the specified vertex. For more on maximally connected component, see http://www.nist.gov/dads/HTML/maximallyConnectedComponent.html.

Parameters:

vertex - the vertex for which the connected set to be returned.

Returns:

a set of all vertices that are in the maximally connected component together with the specified vertex.

connectedSets

public List<Set<V>> connectedSets()

Returns a list of Set s, where each set contains all vertices that are in the same maximally connected component. All graph vertices occur in exactly one set. For more on maximally connected component, see http://www.nist.gov/dads/HTML/maximallyConnectedComponent.html.

Returns:

Returns a list of Set s, where each set contains all vertices that are in the same maximally connected component.

edgeAdded

public void edgeAdded(GraphEdgeChangeEvent<V,E> e)

Description copied from interface: GraphListener

Notifies that an edge has been added to the graph.

Specified by:

edgeAdded in interface GraphListener<V,E>

Parameters:

e - the edge event.

See Also:

GraphListener.edgeAdded(GraphEdgeChangeEvent)

edgeRemoved

public void edgeRemoved(GraphEdgeChangeEvent<V,E> e)

Description copied from interface: GraphListener

Notifies that an edge has been removed from the graph.

Specified by:

edgeRemoved in interface GraphListener<V,E>

Parameters:

e - the edge event.

See Also:

GraphListener.edgeRemoved(GraphEdgeChangeEvent)

pathExists

public boolean pathExists(V sourceVertex,
                          V targetVertex)

Tests whether two vertices lay respectively in the same connected component (undirected graph), or in the same weakly connected component (directed graph).

Parameters:

sourceVertex - one end of the path.

targetVertex - another end of the path.

Returns:

true if and only if the source and target vertex are in the same connected component (undirected graph), or in the same weakly connected component (directed graph).

vertexAdded

public void vertexAdded(GraphVertexChangeEvent<V> e)

Description copied from interface: VertexSetListener

Notifies that a vertex has been added to the graph.

Specified by:

vertexAdded in interface VertexSetListener<V>

Parameters:

e - the vertex event.

See Also:

VertexSetListener.vertexAdded(GraphVertexChangeEvent)

vertexRemoved

public void vertexRemoved(GraphVertexChangeEvent<V> e)

Description copied from interface: VertexSetListener

Notifies that a vertex has been removed from the graph.

Specified by:

vertexRemoved in interface VertexSetListener<V>

Parameters:

e - the vertex event.

See Also:

VertexSetListener.vertexRemoved(GraphVertexChangeEvent)