org.jscience.computing.graph.algorithms
Class ConnectivityInspector

java.lang.Object
  extended by org.jscience.computing.graph.algorithms.ConnectivityInspector
All Implemented Interfaces:
java.util.EventListener, GraphListener, VertexSetListener

public class ConnectivityInspector
extends java.lang.Object
implements GraphListener

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 StrongConnectivityInspector 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.

Since:
Aug 6, 2003

Constructor Summary
ConnectivityInspector(DirectedGraph g)
          Creates a connectivity inspector for the specified directed graph.
ConnectivityInspector(UndirectedGraph g)
          Creates a connectivity inspector for the specified undirected graph.
 
Method Summary
 java.util.Set connectedSetOf(java.lang.Object vertex)
          Returns a set of all vertices that are in the maximally connected component together with the specified vertex.
 java.util.List connectedSets()
          Returns a list of Sets, where each set contains all vertices that are in the same maximally connected component.
 void edgeAdded(GraphEdgeChangeEvent e)
          Notifies that an edge has been added to the graph.
 void edgeRemoved(GraphEdgeChangeEvent e)
          Notifies that an edge has been removed from the graph.
 boolean isGraphConnected()
          Test if the inspected graph is connected.
 boolean pathExists(java.lang.Object sourceVertex, java.lang.Object targetVertex)
          Tests if there is a path from the specified source vertex to the specified target vertices.
 void vertexAdded(GraphVertexChangeEvent e)
          Notifies that a vertex has been added to the graph.
 void vertexRemoved(GraphVertexChangeEvent 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
 

Constructor Detail

ConnectivityInspector

public ConnectivityInspector(UndirectedGraph g)
Creates a connectivity inspector for the specified undirected graph.

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

ConnectivityInspector

public ConnectivityInspector(DirectedGraph g)
Creates a connectivity inspector for the specified directed graph.

Parameters:
g - the graph for which a connectivity inspector to be created.
Method Detail

isGraphConnected

public boolean isGraphConnected()
Test if the inspected graph is connected. An empty graph is not considered connected.

Returns:
true if and only if inspected graph is connected.

connectedSetOf

public java.util.Set connectedSetOf(java.lang.Object 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 java.util.List connectedSets()
Returns a list of Sets, 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 Sets, where each set contains all vertices that are in the same maximally connected component.

edgeAdded

public void edgeAdded(GraphEdgeChangeEvent e)
Description copied from interface: GraphListener
Notifies that an edge has been added to the graph.

Specified by:
edgeAdded in interface GraphListener
Parameters:
e - the edge event.
See Also:
GraphListener.edgeAdded(GraphEdgeChangeEvent)

edgeRemoved

public void edgeRemoved(GraphEdgeChangeEvent e)
Description copied from interface: GraphListener
Notifies that an edge has been removed from the graph.

Specified by:
edgeRemoved in interface GraphListener
Parameters:
e - the edge event.
See Also:
GraphListener.edgeRemoved(GraphEdgeChangeEvent)

pathExists

public boolean pathExists(java.lang.Object sourceVertex,
                          java.lang.Object targetVertex)
Tests if there is a path from the specified source vertex to the specified target vertices. For a directed graph, direction is ignored for this interpretation of path.

Note: Future versions of this method might not ignore edge directions for directed graphs.

Parameters:
sourceVertex - one end of the path.
targetVertex - another end of the path.
Returns:
true if and only if there is a path from the source vertex to the target vertex.

vertexAdded

public void vertexAdded(GraphVertexChangeEvent e)
Description copied from interface: VertexSetListener
Notifies that a vertex has been added to the graph.

Specified by:
vertexAdded in interface VertexSetListener
Parameters:
e - the vertex event.
See Also:
VertexSetListener.vertexAdded(GraphVertexChangeEvent)

vertexRemoved

public void vertexRemoved(GraphVertexChangeEvent e)
Description copied from interface: VertexSetListener
Notifies that a vertex has been removed from the graph.

Specified by:
vertexRemoved in interface VertexSetListener
Parameters:
e - the vertex event.
See Also:
VertexSetListener.vertexRemoved(GraphVertexChangeEvent)