 Type Parameters:
V
 the vertex typeE
 the edge type
 All Implemented Interfaces:
Serializable
,Graph<V,
E>
Graph
interface.
If the base graph is a ListenableGraph
, the subgraph listens on the base
graph and guarantees the subgraph property. If an edge or a vertex is removed from the base
graph, it is automatically removed from the subgraph. Subgraph listeners are informed on such
removal only if it results in a cascaded removal from the subgraph. If the subgraph has been
created as an induced subgraph it also keeps track of edges being added to its vertices. If
vertices are added to the base graph, the subgraph remains unaffected.
If the base graph is not a ListenableGraph, then the subgraph property cannot be guaranteed. If edges or vertices are removed from the base graph, they are not removed from the subgraph.
Modifications to Subgraph are allowed as long as the subgraph property is maintained. Addition of vertices or edges are allowed as long as they also exist in the base graph. Removal of vertices or edges is always allowed. The base graph is never affected by any modification made to the subgraph.
A subgraph may provide a "livewindow" on a base graph, so that changes made to its vertices or
edges are immediately reflected in the base graph, and vice versa. For that to happen, vertices
and edges added to the subgraph must be identical (that is, referenceequal and not only
valueequal) to their respective ones in the base graph. Previous versions of this class enforced
such identity, at a severe performance cost. Currently it is no longer enforced. If you want to
achieve a "livewindow" functionality, your safest tactics would be to NOT override the
equals()
methods of your vertices and edges. If you use a class that has already
overridden the equals()
method, such as String
, then you can use a
wrapper around it, or else use it directly but exercise a great care to avoid having
differentbutequal instances in the subgraph and the base graph.
This graph implementation guarantees deterministic vertex and edge set ordering (via
LinkedHashSet
).
Note that this implementation tries to maintain a "livewindow" on the base graph, which has implications in the performance of the various operations. For example iterating over the adjacent edges of a vertex takes time proportional to the number of adjacent edges of the vertex in the base graph even if the subgraph contains only a small subset of those edges. Therefore, the user must be aware that using this implementation for certain algorithms might come with computational overhead. For certain algorithms it is better to maintain a subgraph by hand instead of using this implementation as a black box.
 Author:
 Barak Naveh
 See Also:

Field Summary
Fields inherited from interface org.jgrapht.Graph
DEFAULT_EDGE_WEIGHT

Constructor Summary
ConstructorDescriptionAsSubgraph
(Graph<V, E> base) Creates a new induced Subgraph with all vertices included.Creates a new induced subgraph.Creates a new subgraph. 
Method Summary
Modifier and TypeMethodDescriptionAdd an edge to the subgraph.boolean
Adds the specified edge to this graph, going from the source vertex to the target vertex.Creates a new vertex in this graph and returns it.boolean
Adds the specified vertex to this subgraph.boolean
containsEdge
(E e) Returnstrue
if this graph contains the specified edge.boolean
containsVertex
(V v) Returnstrue
if this graph contains the specified vertex.int
Returns the degree of the specified vertex.edgeSet()
Returns a set of the edges contained in this graph.Returns a set of all edges touching the specified vertex.getAllEdges
(V sourceVertex, V targetVertex) Returns a set of all edges connecting source vertex to target vertex if such vertices exist in this graph.Returns an edge connecting source vertex to target vertex if such vertices and such edge exist in this graph.getEdgeSource
(E e) Returns the source vertex of an edge.Return the edge supplier that the graph uses whenever it needs to create new edges.getEdgeTarget
(E e) Returns the target vertex of an edge.double
getEdgeWeight
(E e) Returns the weight assigned to a given edge.getType()
Get the graph type.Return the vertex supplier that the graph uses whenever it needs to create new vertices.incomingEdgesOf
(V vertex) Returns a set of all edges incoming into the specified vertex.int
inDegreeOf
(V vertex) Returns the "in degree" of the specified vertex.int
outDegreeOf
(V vertex) Returns the "out degree" of the specified vertex.outgoingEdgesOf
(V vertex) Returns a set of all edges outgoing from the specified vertex.boolean
removeEdge
(E e) Removes the specified edge from the graph.removeEdge
(V sourceVertex, V targetVertex) Removes an edge going from source vertex to target vertex, if such vertices and such edge exist in this graph.boolean
removeVertex
(V v) Removes the specified vertex from this graph including all its touching edges if present.void
setEdgeWeight
(E e, double weight) Assigns a weight to an edge.Returns a set of the vertices contained in this graph.Methods inherited from class org.jgrapht.graph.AbstractGraph
assertVertexExist, containsEdge, equals, hashCode, removeAllEdges, removeAllEdges, removeAllEdges, removeAllVertices, toString, toStringFromSets
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
Methods inherited from interface org.jgrapht.Graph
iterables, setEdgeWeight

Field Details

edgeSet

vertexSet

base

baseType

isInduced
protected final boolean isInduced


Constructor Details

AsSubgraph
Creates a new subgraph. Parameters:
base
 the base (backing) graph on which the subgraph will be based.vertexSubset
 vertices to include in the subgraph. Ifnull
then all vertices are included.edgeSubset
 edges to in include in the subgraph. Ifnull
then all the edges whose vertices found in the graph are included.

AsSubgraph
Creates a new induced subgraph. The subgraph will keep track of edges being added to its vertex subset as well as deletion of edges and vertices. If base it not listenable, this is identical to the call Subgraph(base, vertexSubset, null). Parameters:
base
 the base (backing) graph on which the subgraph will be based.vertexSubset
 vertices to include in the subgraph. Ifnull
then all vertices are included.

AsSubgraph
Creates a new induced Subgraph with all vertices included. The subgraph will keep track of edges being added to its vertex subset as well as deletion of edges and vertices. If base is not listenable, this is identical to the call Subgraph(base, null, null). Parameters:
base
 the base (backing) graph on which the subgraph will be based.


Method Details

getAllEdges
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 isnull
, returnsnull
. 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 interfaceGraph<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
Returns an edge connecting source vertex to target vertex if such vertices and such edge exist in this graph. Otherwise returnsnull
. If any of the specified vertices isnull
returnsnull
In undirected graphs, the returned edge may have its source and target vertices in the opposite order.

getVertexSupplier
Return the vertex supplier that the graph uses whenever it needs to create new vertices.A graph uses the vertex supplier to create new vertex objects whenever a user calls method
Graph.addVertex()
. Users can also create the vertex in user code and then use methodGraph.addVertex(Object)
to add the vertex.In contrast with the
Supplier
interface, the vertex supplier has the additional requirement that a new and distinct result is returned every time it is invoked. More specifically for a new vertex to be added in a graphv
must not be equal to any other vertex in the graph. More formally, the graph must not contain any vertexv2
such thatv2.equals(v)
.Care must also be taken when interchanging calls to methods
Graph.addVertex(Object)
andGraph.addVertex()
. In such a case the user must make sure never to add vertices in the graph using methodGraph.addVertex(Object)
, which are going to be returned in the future by the supplied vertex supplier. Such a sequence will result into anIllegalArgumentException
when calling methodGraph.addVertex()
. Specified by:
getVertexSupplier
in interfaceGraph<V,
E>  Returns:
 the vertex supplier or
null
if the graph has no such supplier

getEdgeSupplier
Return the edge supplier that the graph uses whenever it needs to create new edges.A graph uses the edge supplier to create new edge objects whenever a user calls method
Graph.addEdge(Object, Object)
. Users can also create the edge in user code and then use methodGraph.addEdge(Object, Object, Object)
to add the edge.In contrast with the
Supplier
interface, the edge supplier has the additional requirement that a new and distinct result is returned every time it is invoked. More specifically for a new edge to be added in a graphe
must not be equal to any other edge in the graph (even if the graph allows edgemultiplicity). More formally, the graph must not contain any edgee2
such thate2.equals(e)
. Specified by:
getEdgeSupplier
in interfaceGraph<V,
E>  Returns:
 the edge supplier
null
if the graph has no such supplier

addEdge
Add an edge to the subgraph. The endpoints must exist in the subgraph and the edge must exist in the base graph. In case multiple such edges exist in the base graph, one that is not already in the subgraph is chosen arbitrarily and added to the subgraph. In case all such edges already exist in the subgraph, the method returns null. Specified by:
addEdge
in interfaceGraph<V,
E>  Parameters:
sourceVertex
 the source vertextargetVertex
 the source vertex Returns:
 the added edge or null if all such edges from the base graph already belong in the subgraph
 Throws:
IllegalArgumentException
 if the source or target vertex does not belong to the subgraphIllegalArgumentException
 if the base graph does not contain any edge between the two endpoints See Also:

addEdge
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 edgee2
such thate2.equals(e)
. If this graph already contains such an edge, the call leaves this graph unchanged and returnsfalse
. Some graphs do not allow edgemultiplicity. 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 returnsfalse
. If the edge was added to the graph, returnstrue
.The source and target vertices must already be contained in this graph. If they are not found in graph IllegalArgumentException is thrown.

addVertex
Description copied from interface:Graph
Creates a new vertex in this graph and returns it.This method creates the new vertex
v
using this graph's vertex supplier (seeGraph.getVertexSupplier()
). For the new vertex to be addedv
must not be equal to any other vertex in the graph. More formally, the graph must not contain any vertexv2
such thatv2.equals(v)
. If suchv2
is found then the newly created vertexv
is abandoned, the method leaves this graph unchanged and throws anIllegalArgumentException
.If the underlying graph implementation's
Graph.getVertexSupplier()
returnsnull
, then this method cannot create vertices and throws anUnsupportedOperationException
.Care must also be taken when interchanging calls to methods
Graph.addVertex(Object)
andGraph.addVertex()
. In such a case the user must make sure never to add vertices in the graph using methodGraph.addVertex(Object)
, which are going to be returned in the future by the supplied vertex supplier. Such a sequence will result into anIllegalArgumentException
when calling methodGraph.addVertex()
. 
addVertex
Adds the specified vertex to this subgraph. Specified by:
addVertex
in interfaceGraph<V,
E>  Parameters:
v
 the vertex to be added. Returns:
true
if the vertex was added, otherwisefalse
. Throws:
NullPointerException
 if v is nullIllegalArgumentException
 if the base graph does not contain the vertex See Also:

containsEdge
Returnstrue
if this graph contains the specified edge. More formally, returnstrue
if and only if this graph contains an edgee2
such thate.equals(e2)
. If the specified edge isnull
returnsfalse
. Specified by:
containsEdge
in interfaceGraph<V,
E>  Parameters:
e
 edge whose presence in this graph is to be tested. Returns:
true
if this graph contains the specified edge.

containsVertex
Returnstrue
if this graph contains the specified vertex. More formally, returnstrue
if and only if this graph contains a vertexu
such thatu.equals(v)
. If the specified vertex isnull
returnsfalse
. Specified by:
containsVertex
in interfaceGraph<V,
E>  Parameters:
v
 vertex whose presence in this graph is to be tested. Returns:
true
if this graph contains the specified vertex.

edgeSet
Returns a set of the edges contained in this graph. The set is backed by the graph, so changes to the graph are reflected in the set. If the graph is modified while an iteration over the set is in progress, the results of the iteration are undefined.The graph implementation may maintain a particular set ordering (e.g. via
LinkedHashSet
) for deterministic iteration, but this is not required. It is the responsibility of callers who rely on this behavior to only use graph implementations which support it. 
edgesOf
Returns a set of all edges touching the specified vertex. If no edges are touching the specified vertex returns an empty set. 
degreeOf
Returns the degree of the specified vertex.A degree of a vertex in an undirected graph is the number of edges touching that vertex. Edges with same source and target vertices (selfloops) are counted twice.
In directed graphs this method returns the sum of the "in degree" and the "out degree".
By default this method returns the sum of indegree and outdegree. The exact value returned depends on the types of the underlying graph.

incomingEdgesOf
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 interfaceGraph<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
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 (selfloops) are counted twice.
 Specified by:
inDegreeOf
in interfaceGraph<V,
E>  Parameters:
vertex
 vertex whose degree is to be calculated. Returns:
 the degree of the specified vertex.

outgoingEdgesOf
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 interfaceGraph<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
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 (selfloops) are counted twice.
 Specified by:
outDegreeOf
in interfaceGraph<V,
E>  Parameters:
vertex
 vertex whose degree is to be calculated. Returns:
 the degree of the specified vertex.

removeEdge
Removes the specified edge from the graph. Removes the specified edge from this graph if it is present. More formally, removes an edgee2
such thate2.equals(e)
, if the graph contains such edge. Returnstrue
if the graph contained the specified edge. (The graph will not contain the specified edge once the call returns).If the specified edge is
null
returnsfalse
. Specified by:
removeEdge
in interfaceGraph<V,
E>  Parameters:
e
 edge to be removed from this graph, if present. Returns:
true
if and only if the graph contained the specified edge.

removeEdge
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 ornull
otherwise. Specified by:
removeEdge
in interfaceGraph<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.

removeVertex
Removes the specified vertex from this graph including all its touching edges if present. More formally, if the graph contains a vertexu
such thatu.equals(v)
, the call removes all edges that touchu
and then removesu
itself. If no suchu
is found, the call leaves the graph unchanged. Returnstrue
if the graph contained the specified vertex. (The graph will not contain the specified vertex once the call returns).If the specified vertex is
null
returnsfalse
. Specified by:
removeVertex
in interfaceGraph<V,
E>  Parameters:
v
 vertex to be removed from this graph, if present. Returns:
true
if the graph contained the specified vertex;false
otherwise.

vertexSet
Returns a set of the vertices contained in this graph. The set is backed by the graph, so changes to the graph are reflected in the set. If the graph is modified while an iteration over the set is in progress, the results of the iteration are undefined.The graph implementation may maintain a particular set ordering (e.g. via
LinkedHashSet
) for deterministic iteration, but this is not required. It is the responsibility of callers who rely on this behavior to only use graph implementations which support it. 
getEdgeSource
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 interfaceGraph<V,
E>  Parameters:
e
 edge of interest Returns:
 source vertex

getEdgeTarget
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 interfaceGraph<V,
E>  Parameters:
e
 edge of interest Returns:
 target vertex

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, selfloops, multiple (parallel) edges, weights, etc. 
getEdgeWeight
Returns the weight assigned to a given edge. Unweighted graphs return 1.0 (as defined byGraph.DEFAULT_EDGE_WEIGHT
), allowing weightedgraph algorithms to apply to them when meaningful. Specified by:
getEdgeWeight
in interfaceGraph<V,
E>  Parameters:
e
 edge of interest Returns:
 edge weight

setEdgeWeight
Assigns a weight to an edge. Specified by:
setEdgeWeight
in interfaceGraph<V,
E>  Parameters:
e
 edge on which to set weightweight
 new weight for edge
