Class Subgraph<V,E,G extends Graph<V,E>>
- java.lang.Object
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- org.jgrapht.graph.AbstractGraph<V,E>
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- org.jgrapht.graph.Subgraph<V,E,G>
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- Type Parameters:
V
- the vertex typeE
- the edge typeG
- the type of the base graph
- All Implemented Interfaces:
java.io.Serializable
,Graph<V,E>
- Direct Known Subclasses:
DirectedSubgraph
,UndirectedSubgraph
public class Subgraph<V,E,G extends Graph<V,E>> extends AbstractGraph<V,E> implements java.io.Serializable
A subgraph is a graph that has a subset of vertices and a subset of edges with respect to some base graph. More formally, a subgraph G(V,E) that is based on a base graph Gb(Vb,Eb) satisfies the following subgraph property: V is a subset of Vb and E is a subset of Eb. Other than this property, a subgraph is a graph with any respect and fully complies with theGraph
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 "live-window" 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, reference-equal and not only value-equal) 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 "live-window" 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 theequals()
method, such asString
, than you can use a wrapper around it, or else use it directly but exercise a great care to avoid having different-but-equal 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 "live-window" 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.
- Since:
- Jul 18, 2003
- See Also:
Graph
,Set
, Serialized Form
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Nested Class Summary
Nested Classes Modifier and Type Class Description private class
Subgraph.BaseGraphListener
An internal listener on the base graph.
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Field Summary
Fields Modifier and Type Field Description protected G
base
protected java.util.Set<E>
edgeSet
protected boolean
isInduced
private static java.lang.String
NO_SUCH_EDGE_IN_BASE
private static java.lang.String
NO_SUCH_VERTEX_IN_BASE
private static long
serialVersionUID
private java.util.Set<E>
unmodifiableEdgeSet
private java.util.Set<V>
unmodifiableVertexSet
protected java.util.Set<V>
vertexSet
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Constructor Summary
Constructors Constructor Description Subgraph(G base)
Creates a new induced Subgraph with all vertices included.Subgraph(G base, java.util.Set<? extends V> vertexSubset)
Creates a new induced Subgraph.Subgraph(G base, java.util.Set<? extends V> vertexSubset, java.util.Set<? extends E> edgeSubset)
Creates a new Subgraph.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description E
addEdge(V sourceVertex, V targetVertex)
Add an edge to the subgraph.boolean
addEdge(V sourceVertex, V targetVertex, E e)
Adds the specified edge to this graph, going from the source vertex to the target vertex.boolean
addVertex(V v)
Adds the specified vertex to this subgraph.boolean
containsEdge(E e)
Returns true if this graph contains the specified edge.boolean
containsVertex(V v)
Returns true if this graph contains the specified vertex.java.util.Set<E>
edgeSet()
Returns a set of the edges contained in this graph.java.util.Set<E>
edgesOf(V vertex)
Returns a set of all edges touching the specified vertex.java.util.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.G
getBase()
Get the base graph.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.EdgeFactory<V,E>
getEdgeFactory()
Returns the edge factory using which this graph creates new edges.V
getEdgeSource(E e)
Returns the source vertex of an edge.V
getEdgeTarget(E e)
Returns the target vertex of an edge.double
getEdgeWeight(E e)
Returns the weight assigned to a given edge.private void
initialize(java.util.Set<? extends V> vertexFilter, java.util.Set<? extends E> edgeFilter)
boolean
removeEdge(E e)
Removes the specified edge from the graph.E
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.java.util.Set<V>
vertexSet()
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
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Field Detail
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serialVersionUID
private static final long serialVersionUID
- See Also:
- Constant Field Values
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NO_SUCH_EDGE_IN_BASE
private static final java.lang.String NO_SUCH_EDGE_IN_BASE
- See Also:
- Constant Field Values
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NO_SUCH_VERTEX_IN_BASE
private static final java.lang.String NO_SUCH_VERTEX_IN_BASE
- See Also:
- Constant Field Values
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edgeSet
protected final java.util.Set<E> edgeSet
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vertexSet
protected final java.util.Set<V> vertexSet
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isInduced
protected final boolean isInduced
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unmodifiableEdgeSet
private transient java.util.Set<E> unmodifiableEdgeSet
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unmodifiableVertexSet
private transient java.util.Set<V> unmodifiableVertexSet
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Constructor Detail
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Subgraph
public Subgraph(G base, java.util.Set<? extends V> vertexSubset, java.util.Set<? extends E> edgeSubset)
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.
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Subgraph
public Subgraph(G base, java.util.Set<? extends V> vertexSubset)
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.
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Subgraph
public Subgraph(G base)
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 it 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.
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Method Detail
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getAllEdges
public java.util.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 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.
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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 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.
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getEdgeFactory
public EdgeFactory<V,E> getEdgeFactory()
Returns the edge factory using which this graph creates new edges. The edge factory is defined when the graph is constructed and must not be modified.- Specified by:
getEdgeFactory
in interfaceGraph<V,E>
- Returns:
- the edge factory using which this graph creates new edges.
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addEdge
public E addEdge(V sourceVertex, V targetVertex)
Add an edge to the subgraph. The end-points 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:
java.lang.IllegalArgumentException
- if the source or target vertex does not belong to the subgraphjava.lang.IllegalArgumentException
- if the base graph does not contain any edge between the two end-points- See Also:
Graph.getEdgeFactory()
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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 edgee2
such thate2.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 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.
- Specified by:
addEdge
in interfaceGraph<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.
- See Also:
Graph.addEdge(Object, Object)
,Graph.getEdgeFactory()
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addVertex
public boolean addVertex(V v)
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:
java.lang.NullPointerException
- if v is nulljava.lang.IllegalArgumentException
- if the base graph does not contain the vertex- See Also:
Subgraph
,Graph.addVertex(Object)
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containsEdge
public boolean containsEdge(E e)
Returns true if this graph contains the specified edge. More formally, returns true 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.
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containsVertex
public boolean containsVertex(V v)
Returns true if this graph contains the specified vertex. More formally, returns true 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.
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edgeSet
public java.util.Set<E> 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.
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edgesOf
public java.util.Set<E> edgesOf(V vertex)
Returns a set of all edges touching the specified vertex. If no edges are touching the specified vertex returns an empty set.
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removeEdge
public boolean removeEdge(E e)
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. Returns true 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.
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removeEdge
public E 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. 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.
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removeVertex
public boolean removeVertex(V v)
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. Returns true 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.
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vertexSet
public java.util.Set<V> 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.
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getEdgeSource
public V getEdgeSource(E e)
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
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getEdgeTarget
public V getEdgeTarget(E e)
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
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getBase
public G getBase()
Get the base graph.- Returns:
- the base graph
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getEdgeWeight
public double getEdgeWeight(E e)
Returns the weight assigned to a given edge. Unweighted graphs return 1.0 (as defined byWeightedGraph.DEFAULT_EDGE_WEIGHT
), allowing weighted-graph algorithms to apply to them where meaningful.- Specified by:
getEdgeWeight
in interfaceGraph<V,E>
- Parameters:
e
- edge of interest- Returns:
- edge weight
- See Also:
WeightedGraph
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setEdgeWeight
public void setEdgeWeight(E e, double weight)
Assigns a weight to an edge.- Parameters:
e
- edge on which to set weightweight
- new weight for edge- See Also:
WeightedGraph.setEdgeWeight(Object, double)
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