Package org.jgrapht.alg.connectivity

Class ConnectivityInspector<V,​E>

  • Type Parameters:
    V - the graph vertex type
    E - the graph edge type
    All Implemented Interfaces:
    java.util.EventListener, GraphListener<V,​E>, VertexSetListener<V>
    public class ConnectivityInspector<V,​E>
extends java.lang.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 Description
      ConnectivityInspector​(Graph<V,​E> g)
      Creates a connectivity inspector for the specified graph.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      java.util.Set<V> connectedSetOf​(V vertex)
      Returns a set of all vertices that are in the maximally connected component together with the specified vertex.
      java.util.List<java.util.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

    • 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 java.util.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 java.util.List<java.util.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.

      • 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).