V
 the graph vertex typeE
 the graph edge typepublic class AsSynchronizedGraph<V,E> extends GraphDelegator<V,E> implements Graph<V,E>, Serializable
Users need to manually synchronize on edge supplier (see Graph.getEdgeSupplier()
) if
creating an edge needs to access shared resources. Failure to follow this advice may result in
nondeterministic behavior.
For all methods returning a Set, the Graph guarantees that all operations on the returned Set do
not affect the backing Graph. For edgeSet
and vertexSet
methods, the
returned Set is backed by the underlying graph, but when a traversal over the set is started via
a method such as iterator(), a snapshot of the underlying Set is copied for iteration purposes.
For edgesOf
, incomingEdgesOf
and outgoingEdgesOf
methods,
the returned Set is a unmodifiable copy of the result produced by the underlying Graph. Users can
control whether those copies should be cached; caching may significantly increase memory
requirements. If users decide to cache those copies and the backing graph's changes don't affect
them, those copies will be returned the next time the method is called. If the backing graph's
changes affect them, they will be removed from cache and recreated the next time the method is
called. If users decide to not cache those copies, the graph will create ephemeral copies every
time the method is called. For other methods returning a Set, the Set is just the backing Graph's
return.
As an alternative, a copyless mode is supported. When enabled, no collection copies are
made at all (and hence the cache setting is ignored). This requires the caller to explicitly
synchronize iteration via the getLock()
method. This approach requires quite a bit of care
on the part of the calling application, so it is disabled by default.
Even though this graph implementation is threadsafe, callers should still be aware of potential
hazards from removal methods. If calling code obtains a reference to a vertex or edge from the
graph, and then calls another graph method to access information about that object, an
IllegalArgumentException
may be thrown if another thread has concurrently removed that
object. Therefore, calling the remove methods concurrently with a typical algorithm is likely to
cause the algorithm to fail with an IllegalArgumentException
. So really the main
concurrent read/write use case is addonly.
eg: If threadA tries to get all edges touching a certain vertex after threadB removes the vertex,
the algorithm will be interrupted by IllegalArgumentException
.
Thread threadA = new Thread(() > {
Set vertices = graph.vertexSet();
for (Object v : vertices) {
// IllegalArgumentException
may be thrown since other threads may have removed
// the vertex.
Set edges = graph.edgesOf(v);
doOtherThings();
}
});
Thread threadB = new Thread(() > {
Set vertices = graph.vertexSet();
for (Object v : vertices) {
if (someConditions) {
graph.removeVertex(v);
}
}
});
One way to avoid the hazard noted above is for the calling application to explicitly synchronize
all iterations using the getLock()
method.
The created Graph's hashCode is equal to the backing set's hashCode. And the created Graph is equal to another Graph if they are the same Graph or the backing Graph is equal to the other Graph.
Modifier and Type  Class and Description 

static class 
AsSynchronizedGraph.Builder<V,E>
A builder for
AsSynchronizedGraph . 
DEFAULT_EDGE_WEIGHT
Constructor and Description 

AsSynchronizedGraph(Graph<V,E> g)
Constructor for AsSynchronizedGraph with default settings (cache disabled, nonfair mode, and
copyless mode disabled).

Modifier and Type  Method and Description 

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.

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 graph if not already present.

boolean 
containsEdge(E e)
Returns true if this graph contains the specified edge.

boolean 
containsEdge(V sourceVertex,
V targetVertex)
Returns true if and only if this graph contains an edge going from the source vertex
to the target vertex.

boolean 
containsVertex(V v)
Returns true if this graph contains the specified vertex.

int 
degreeOf(V vertex)
Returns the degree of the specified vertex.

Set<E> 
edgeSet()
Returns a set of the edges contained in this graph.

Set<E> 
edgesOf(V vertex)
Returns a set of all edges touching the specified vertex.

boolean 
equals(Object o)
Indicates whether some other object is "equal to" this graph.

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.

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.

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.

ReentrantReadWriteLock 
getLock()
Get the read/write lock used to synchronize all access to this graph.

int 
hashCode()
Returns a hash code value for this graph.

Set<E> 
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.

boolean 
isCacheEnabled()
Return whether the graph uses cache for
edgesOf , incomingEdgesOf
and outgoingEdgesOf methods. 
boolean 
isCopyless()
Return whether copyless mode is used for collectionreturning methods.

boolean 
isFair()
Return whether fair mode is used for synchronizing access to this graph.

int 
outDegreeOf(V vertex)
Returns the "out degree" of the specified vertex.

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

boolean 
removeAllEdges(Collection<? extends E> edges)
Removes all the edges in this graph that are also contained in the specified edge collection.

Set<E> 
removeAllEdges(V sourceVertex,
V targetVertex)
Removes all the edges going from the specified source vertex to the specified target vertex,
and returns a set of all removed edges.

boolean 
removeAllVertices(Collection<? extends V> vertices)
Removes all the vertices in this graph that are also contained in the specified vertex
collection.

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.

AsSynchronizedGraph<V,E> 
setCache(boolean cacheEnabled)
Set the cache strategy for
edgesOf , incomingEdgesOf and
outgoingEdgesOf methods. 
void 
setEdgeWeight(E e,
double weight)
Assigns a weight to an edge.

String 
toString()
Returns a string of the parenthesized pair (V, E) representing this G=(V,E) graph.

Set<V> 
vertexSet()
Returns a set of the vertices contained in this graph.

addVertex, getDelegate, getEdgeSupplier, getType, getVertexSupplier
assertVertexExist, removeAllEdges, toStringFromSets
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
addVertex, getEdgeSupplier, getType, getVertexSupplier, setEdgeWeight
public Set<E> getAllEdges(V sourceVertex, V targetVertex)
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.
getAllEdges
in interface Graph<V,E>
getAllEdges
in class GraphDelegator<V,E>
sourceVertex
 source vertex of the edge.targetVertex
 target vertex of the edge.public E getEdge(V sourceVertex, V targetVertex)
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.
public E addEdge(V sourceVertex, V targetVertex)
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 edgemultiplicity). 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
.
addEdge
in interface Graph<V,E>
addEdge
in class GraphDelegator<V,E>
sourceVertex
 source vertex of the edge.targetVertex
 target vertex of the edge.
null
.Graph.getEdgeSupplier()
public boolean addEdge(V sourceVertex, V targetVertex, E e)
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 edgemultiplicity. 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.
addEdge
in interface Graph<V,E>
addEdge
in class GraphDelegator<V,E>
sourceVertex
 source vertex of the edge.targetVertex
 target vertex of the edge.e
 edge to be added to this graph.Graph.addEdge(Object, Object)
,
Graph.getEdgeSupplier()
public boolean addVertex(V v)
v
, to this graph if this graph contains no vertex
u
such that
u.equals(v)
. If this graph already contains such vertex, the call leaves this graph
unchanged and returns false. In combination with the restriction on constructors,
this ensures that graphs never contain duplicate vertices.public boolean containsEdge(V sourceVertex, V targetVertex)
null
, returns false
.containsEdge
in interface Graph<V,E>
containsEdge
in class AbstractGraph<V,E>
sourceVertex
 source vertex of the edge.targetVertex
 target vertex of the edge.Graph.containsEdge(Object, Object)
public boolean containsEdge(E e)
e2
such that
e.equals(e2)
. If the specified edge is null
returns
false
.containsEdge
in interface Graph<V,E>
containsEdge
in class GraphDelegator<V,E>
e
 edge whose presence in this graph is to be tested.public boolean containsVertex(V v)
u
such that
u.equals(v)
. If the specified vertex is null
returns
false
.containsVertex
in interface Graph<V,E>
containsVertex
in class GraphDelegator<V,E>
v
 vertex whose presence in this graph is to be tested.public int degreeOf(V vertex)
public Set<E> edgeSet()
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.
public Set<E> edgesOf(V vertex)
public int inDegreeOf(V 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.
inDegreeOf
in interface Graph<V,E>
inDegreeOf
in class GraphDelegator<V,E>
vertex
 vertex whose degree is to be calculated.public Set<E> incomingEdgesOf(V 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.
incomingEdgesOf
in interface Graph<V,E>
incomingEdgesOf
in class GraphDelegator<V,E>
vertex
 the vertex for which the list of incoming edges to be returned.public int outDegreeOf(V 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.
outDegreeOf
in interface Graph<V,E>
outDegreeOf
in class GraphDelegator<V,E>
vertex
 vertex whose degree is to be calculated.public Set<E> outgoingEdgesOf(V 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.
outgoingEdgesOf
in interface Graph<V,E>
outgoingEdgesOf
in class GraphDelegator<V,E>
vertex
 the vertex for which the list of outgoing edges to be returned.public boolean removeAllEdges(Collection<? extends E> edges)
Graph.removeEdge(Object)
method.removeAllEdges
in interface Graph<V,E>
removeAllEdges
in class AbstractGraph<V,E>
edges
 edges to be removed from this graph.Graph.removeAllEdges(Collection)
public Set<E> removeAllEdges(V sourceVertex, V targetVertex)
null
if any of the specified
vertices does not exist in the graph. If both vertices exist but no edge is found, returns an
empty set. This method will either invoke the Graph.removeEdge(Object)
method, or the
Graph.removeEdge(Object, Object)
method.removeAllEdges
in interface Graph<V,E>
removeAllEdges
in class AbstractGraph<V,E>
sourceVertex
 source vertex of the edge.targetVertex
 target vertex of the edge.null
if either vertex is not part of graphGraph.removeAllEdges(Object, Object)
public boolean removeAllVertices(Collection<? extends V> vertices)
Graph.removeVertex(Object)
method.removeAllVertices
in interface Graph<V,E>
removeAllVertices
in class AbstractGraph<V,E>
vertices
 vertices to be removed from this graph.Graph.removeAllVertices(Collection)
public boolean removeEdge(E e)
e2
such that e2.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
returns
false
.
removeEdge
in interface Graph<V,E>
removeEdge
in class GraphDelegator<V,E>
e
 edge to be removed from this graph, if present.true
if and only if the graph contained the specified edge.public E removeEdge(V sourceVertex, V targetVertex)
null
otherwise.removeEdge
in interface Graph<V,E>
removeEdge
in class GraphDelegator<V,E>
sourceVertex
 source vertex of the edge.targetVertex
 target vertex of the edge.null
if no edge removed.public boolean removeVertex(V v)
u
such that u.equals(v)
, the call removes all edges that touch
u
and then removes u
itself. If no such u
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
returns
false
.
removeVertex
in interface Graph<V,E>
removeVertex
in class GraphDelegator<V,E>
v
 vertex to be removed from this graph, if present.true
if the graph contained the specified vertex; false
otherwise.public String toString()
toString
in class GraphDelegator<V,E>
public Set<V> vertexSet()
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.
public V getEdgeSource(E e)
getEdgeSource
in interface Graph<V,E>
getEdgeSource
in class GraphDelegator<V,E>
e
 edge of interestpublic V getEdgeTarget(E e)
getEdgeTarget
in interface Graph<V,E>
getEdgeTarget
in class GraphDelegator<V,E>
e
 edge of interestpublic double getEdgeWeight(E e)
Graph.DEFAULT_EDGE_WEIGHT
), allowing weightedgraph algorithms to apply to them when
meaningful.getEdgeWeight
in interface Graph<V,E>
getEdgeWeight
in class GraphDelegator<V,E>
e
 edge of interestpublic void setEdgeWeight(E e, double weight)
setEdgeWeight
in interface Graph<V,E>
setEdgeWeight
in class GraphDelegator<V,E>
e
 edge on which to set weightweight
 new weight for edgepublic boolean isCacheEnabled()
edgesOf
, incomingEdgesOf
and outgoingEdgesOf
methods.public boolean isCopyless()
public AsSynchronizedGraph<V,E> setCache(boolean cacheEnabled)
edgesOf
, incomingEdgesOf
and
outgoingEdgesOf
methods.cacheEnabled
 a flag whether to use cache for those methods, if true, cache
will be used for those methods, otherwise cache will not be used.public int hashCode()
hashCode
in class AbstractGraph<V,E>
Object.hashCode()
public boolean equals(Object o)
true
if
the given object is also a graph, the two graphs are instances of the same graph class, have
identical vertices and edges sets with the same weights.equals
in class AbstractGraph<V,E>
o
 object to be compared for equality with this graphtrue
if the specified object is equal to this graphObject.equals(Object)
public boolean isFair()
public ReentrantReadWriteLock getLock()
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