## Class EdgeReversedGraph<V,​E>

• Type Parameters:
V - the graph vertex type
E - the graph edge type
All Implemented Interfaces:
Serializable, Graph<V,​E>

public class EdgeReversedGraph<V,​E>
extends GraphDelegator<V,​E>
implements Graph<V,​E>
Provides an edge-reversed view $g'$ of a directed graph $g$. The vertex sets for the two graphs are the same, but g' contains an edge $(v2, v1)$ iff g contains an edge $(v1, v2)$. $g'$ is backed by $g$, so changes to $g$ are reflected in $g'$, and vice versa.

This class allows you to use a directed graph algorithm in reverse. For example, suppose you have a directed graph representing a tree, with edges from parent to child, and you want to find all of the parents of a node. To do this, simply create an edge-reversed graph and pass that as input to DepthFirstIterator.

Author:
John V. Sichi
AsUndirectedGraph, Serialized Form
• ### Constructor Detail

• #### EdgeReversedGraph

public EdgeReversedGraph​(Graph<V,​E> g)
Creates a new EdgeReversedGraph.
Parameters:
g - the base (backing) graph on which the edge-reversed view will be based.
• ### Method Detail

• #### getEdge

public E getEdge​(V sourceVertex,
V targetVertex)
Description copied from class: GraphDelegator
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.
Graph.getEdge(Object, Object)
• #### getAllEdges

public Set<E> getAllEdges​(V sourceVertex,
V targetVertex)
Description copied from class: GraphDelegator
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.
Graph.getAllEdges(Object, Object)

V targetVertex)
Description copied from class: GraphDelegator
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, than 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:
Overrides:
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.

V targetVertex,
E e)
Description copied from class: GraphDelegator
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, than 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:
Overrides:
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.
• #### inDegreeOf

public int inDegreeOf​(V vertex)
Description copied from class: GraphDelegator
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.
Graph.inDegreeOf(Object)
• #### outDegreeOf

public int outDegreeOf​(V vertex)
Description copied from class: GraphDelegator
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.
Graph.outDegreeOf(Object)
• #### incomingEdgesOf

public Set<E> incomingEdgesOf​(V vertex)
Description copied from class: GraphDelegator
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.
Graph.incomingEdgesOf(Object)
• #### outgoingEdgesOf

public Set<E> outgoingEdgesOf​(V vertex)
Description copied from class: GraphDelegator
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.
Graph.outgoingEdgesOf(Object)
• #### removeEdge

public E removeEdge​(V sourceVertex,
V targetVertex)
Description copied from class: GraphDelegator
Removes an edge going from source vertex to target vertex, if such vertices and such edge exist in this graph. Returns the edge if removed or null otherwise.
Specified by:
removeEdge in interface Graph<V,​E>
Overrides:
removeEdge in class GraphDelegator<V,​E>
Parameters:
sourceVertex - source vertex of the edge.
targetVertex - target vertex of the edge.
Returns:
The removed edge, or null if no edge removed.
Graph.removeEdge(Object, Object)
• #### getEdgeSource

public V getEdgeSource​(E e)
Description copied from class: GraphDelegator
Returns the source vertex of an edge. For an undirected graph, source and target are distinguishable designations (but without any mathematical meaning).
Specified by:
getEdgeSource in interface Graph<V,​E>
Overrides:
getEdgeSource in class GraphDelegator<V,​E>
Parameters:
e - edge of interest
Returns:
source vertex
Graph.getEdgeSource(Object)
• #### getEdgeTarget

public V getEdgeTarget​(E e)
Description copied from class: GraphDelegator
Returns the target vertex of an edge. For an undirected graph, source and target are distinguishable designations (but without any mathematical meaning).
Specified by:
getEdgeTarget in interface Graph<V,​E>
Overrides:
getEdgeTarget in class GraphDelegator<V,​E>
Parameters:
e - edge of interest
Returns:
target vertex