Module org.jgrapht.core
Package org.jgrapht.graph

Class AsUndirectedGraph<V,E>

java.lang.Object
org.jgrapht.graph.AbstractGraph<V,E>
org.jgrapht.graph.GraphDelegator<V,E>
org.jgrapht.graph.AsUndirectedGraph<V,E>
Type Parameters:
V - the graph vertex type
E - the graph edge type
All Implemented Interfaces:
Serializable, Graph<V,E>
public class AsUndirectedGraph<V,E> extends GraphDelegator<V,E> implements Serializable, Graph<V,E>
An undirected view of the backing directed graph specified in the constructor. This graph allows modules to apply algorithms designed for undirected graphs to a directed graph by simply ignoring edge direction. If the backing directed graph is an oriented graph, then the view will be a simple graph; otherwise, it will be a multigraph. Query operations on this graph "read through" to the backing graph. Attempts to add edges will result in an UnsupportedOperationException, but vertex addition/removal and edge removal are all supported (and immediately reflected in the backing graph).

Note that edges returned by this graph's accessors are really just the edges of the underlying directed graph. Since there is no interface distinction between directed and undirected edges, this detail should be irrelevant to algorithms.

This graph does not pass the hashCode and equals operations through to the backing graph, but relies on Object's equals and hashCode methods. This graph will be serializable if the backing graph is serializable.

Author:
John V. Sichi
See Also:

  • Constructor Details

    • AsUndirectedGraph

      public AsUndirectedGraph(Graph<V,E> g)
      Constructor for AsUndirectedGraph.
      Parameters:
      g - the backing directed graph over which an undirected view is to be created.
      Throws:
      IllegalArgumentException - if the graph is not directed

  • Method Details

    • getAllEdges

      public Set<E> getAllEdges(V sourceVertex, V targetVertex)
      Returns a set of all edges connecting source vertex to target vertex if such vertices exist in this graph. If any of the vertices does not exist or is null, returns null. If both vertices exist but no edges found, returns an empty set.

      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.

      Specified by:
      getAllEdges in interface Graph<V,E>
      Overrides:
      getAllEdges in class GraphDelegator<V,E>
      Parameters:
      sourceVertex - source vertex of the edge.
      targetVertex - target vertex of the edge.
      Returns:
      a set of all edges connecting source vertex to target vertex.

    • getEdge

      public E getEdge(V sourceVertex, V targetVertex)
      Returns an edge connecting source vertex to target vertex if such vertices and such edge exist in this graph. Otherwise returns null. If any of the specified vertices is null returns null

      In undirected graphs, the returned edge may have its source and target vertices in the opposite order.

      Specified by:
      getEdge in interface Graph<V,E>
      Overrides:
      getEdge in class GraphDelegator<V,E>
      Parameters:
      sourceVertex - source vertex of the edge.
      targetVertex - target vertex of the edge.
      Returns:
      an edge connecting source vertex to target vertex.

    • addEdge

      public E addEdge(V sourceVertex, V targetVertex)
      Creates a new edge in this graph, going from the source vertex to the target vertex, and returns the created edge. Some graphs do not allow edge-multiplicity. In such cases, if the graph already contains an edge from the specified source to the specified target, then this method does not change the graph and returns null.

      The source and target vertices must already be contained in this graph. If they are not found in graph IllegalArgumentException is thrown.

      This method creates the new edge e using this graph's edge supplier (see Graph.getEdgeSupplier()). For the new edge to be added e must not be equal to any other edge the graph (even if the graph allows edge-multiplicity). More formally, the graph must not contain any edge e2 such that e2.equals(e). If such e2 is found then the newly created edge e is abandoned, the method leaves this graph unchanged and returns null.

      If the underlying graph implementation's Graph.getEdgeSupplier() returns null, then this method cannot create edges and throws an UnsupportedOperationException.

      Specified by:
      addEdge in interface Graph<V,E>
      Overrides:
      addEdge in class GraphDelegator<V,E>
      Parameters:
      sourceVertex - source vertex of the edge.
      targetVertex - target vertex of the edge.
      Returns:
      The newly created edge if added to the graph, otherwise null.
      Throws:
      UnsupportedOperationException - always, since operation is unsupported
      See Also:

    • addEdge

      public boolean addEdge(V sourceVertex, V targetVertex, E e)
      Adds the specified edge to this graph, going from the source vertex to the target vertex. More formally, adds the specified edge, e, to this graph if this graph contains no edge e2 such that e2.equals(e). If this graph already contains such an edge, the call leaves this graph unchanged and returns false. Some graphs do not allow edge-multiplicity. In such cases, if the graph already contains an edge from the specified source to the specified target, then this method does not change the graph and returns false. If the edge was added to the graph, returns true.

      The source and target vertices must already be contained in this graph. If they are not found in graph IllegalArgumentException is thrown.

      Specified by:
      addEdge in interface Graph<V,E>
      Overrides:
      addEdge in class GraphDelegator<V,E>
      Parameters:
      sourceVertex - source vertex of the edge.
      targetVertex - target vertex of the edge.
      e - edge to be added to this graph.
      Returns:
      true if this graph did not already contain the specified edge.
      Throws:
      UnsupportedOperationException - always, since operation is unsupported
      See Also:

    • degreeOf

      public int degreeOf(V vertex)
      Returns the degree of the specified vertex.
      Specified by:
      degreeOf in interface Graph<V,E>
      Overrides:
      degreeOf in class GraphDelegator<V,E>
      Parameters:
      vertex - vertex whose degree is to be calculated
      Returns:
      the degree of the specified vertex

    • incomingEdgesOf

      public Set<E> incomingEdgesOf(V vertex)
      Returns a set of all edges incoming into the specified vertex.

      In the case of undirected graphs this method returns all edges touching the vertex, thus, some of the returned edges may have their source and target vertices in the opposite order.

      Specified by:
      incomingEdgesOf in interface Graph<V,E>
      Overrides:
      incomingEdgesOf in class GraphDelegator<V,E>
      Parameters:
      vertex - the vertex for which the list of incoming edges to be returned.
      Returns:
      a set of all edges incoming into the specified vertex.

    • inDegreeOf

      public int inDegreeOf(V 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.

      Specified by:
      inDegreeOf in interface Graph<V,E>
      Overrides:
      inDegreeOf in class GraphDelegator<V,E>
      Parameters:
      vertex - vertex whose degree is to be calculated.
      Returns:
      the degree of the specified vertex.

    • outgoingEdgesOf

      public Set<E> outgoingEdgesOf(V vertex)
      Returns a set of all edges outgoing from the specified vertex.

      In the case of undirected graphs this method returns all edges touching the vertex, thus, some of the returned edges may have their source and target vertices in the opposite order.

      Specified by:
      outgoingEdgesOf in interface Graph<V,E>
      Overrides:
      outgoingEdgesOf in class GraphDelegator<V,E>
      Parameters:
      vertex - the vertex for which the list of outgoing edges to be returned.
      Returns:
      a set of all edges outgoing from the specified vertex.

    • outDegreeOf

      public int outDegreeOf(V 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.

      Specified by:
      outDegreeOf in interface Graph<V,E>
      Overrides:
      outDegreeOf in class GraphDelegator<V,E>
      Parameters:
      vertex - vertex whose degree is to be calculated.
      Returns:
      the degree of the specified vertex.

    • getType

      public GraphType getType()
      Get the graph type. The graph type can be used to query for additional metadata such as whether the graph supports directed or undirected edges, self-loops, multiple (parallel) edges, weights, etc.
      Specified by:
      getType in interface Graph<V,E>
      Overrides:
      getType in class GraphDelegator<V,E>
      Returns:
      the graph type

    • toString

      public String toString()
      Returns a string of the parenthesized pair (V, E) representing this G=(V,E) graph. 'V' is the string representation of the vertex set, and 'E' is the string representation of the edge set.
      Overrides:
      toString in class GraphDelegator<V,E>
      Returns:
      a string representation of this graph.