Interface Network<N,E>

 Type Parameters:
N
 Node parameter typeE
 Edge parameter type
 All Superinterfaces:
PredecessorsFunction<N>
,SuccessorsFunction<N>
 All Known Subinterfaces:
MutableNetwork<N,E>
 All Known Implementing Classes:
AbstractNetwork
,ImmutableNetwork
@Beta @DoNotMock("Use NetworkBuilder to create a real instance") public interface Network<N,E> extends SuccessorsFunction<N>, PredecessorsFunction<N>
An interface for graphstructured data, whose edges are unique objects.A graph is composed of a set of nodes and a set of edges connecting pairs of nodes.
There are three primary interfaces provided to represent graphs. In order of increasing complexity they are:
Graph
,ValueGraph
, andNetwork
. You should generally prefer the simplest interface that satisfies your use case. See the "Choosing the right graph type" section of the Guava User Guide for more details.Capabilities
Network
supports the following use cases (definitions of terms): directed graphs
 undirected graphs
 graphs that do/don't allow parallel edges
 graphs that do/don't allow selfloops
 graphs whose nodes/edges are insertionordered, sorted, or unordered
 graphs whose edges are unique objects
Building a
Network
The implementation classes that
common.graph
provides are not public, by design. To create an instance of one of the builtin implementations ofNetwork
, use theNetworkBuilder
class:MutableNetwork<Integer, MyEdge> graph = NetworkBuilder.directed().build();
NetworkBuilder.build()
returns an instance ofMutableNetwork
, which is a subtype ofNetwork
that provides methods for adding and removing nodes and edges. If you do not need to mutate a graph (e.g. if you write a method than runs a readonly algorithm on the graph), you should use the nonmutatingNetwork
interface, or anImmutableNetwork
.You can create an immutable copy of an existing
Network
usingImmutableNetwork.copyOf(Network)
:ImmutableNetwork<Integer, MyEdge> immutableGraph = ImmutableNetwork.copyOf(graph);
Instances of
ImmutableNetwork
do not implementMutableNetwork
(obviously!) and are contractually guaranteed to be unmodifiable and threadsafe.The Guava User Guide has more information on (and examples of) building graphs.
Additional documentation
See the Guava User Guide for the
common.graph
package ("Graphs Explained") for additional documentation, including: Since:
 20.0
 Author:
 James Sexton, Joshua O'Madadhain


Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description Set<E>
adjacentEdges(E edge)
Returns the edges which have anincident node
in common withedge
.Set<N>
adjacentNodes(N node)
Returns the nodes which have an incident edge in common withnode
in this network.boolean
allowsParallelEdges()
Returns true if this network allows parallel edges.boolean
allowsSelfLoops()
Returns true if this network allows selfloops (edges that connect a node to itself).Graph<N>
asGraph()
Returns a live view of this network as aGraph
.int
degree(N node)
Returns the count ofnode
'sincident edges
, counting selfloops twice (equivalently, the number of times an edge touchesnode
).Optional<E>
edgeConnecting(EndpointPair<N> endpoints)
Returns the single edge that directly connectsendpoints
(in the order, if any, specified byendpoints
), if one is present, orOptional.empty()
if no such edge exists.Optional<E>
edgeConnecting(N nodeU, N nodeV)
Returns the single edge that directly connectsnodeU
tonodeV
, if one is present, orOptional.empty()
if no such edge exists.@Nullable E
edgeConnectingOrNull(EndpointPair<N> endpoints)
Returns the single edge that directly connectsendpoints
(in the order, if any, specified byendpoints
), if one is present, ornull
if no such edge exists.@Nullable E
edgeConnectingOrNull(N nodeU, N nodeV)
Returns the single edge that directly connectsnodeU
tonodeV
, if one is present, ornull
if no such edge exists.ElementOrder<E>
edgeOrder()
Returns the order of iteration for the elements ofedges()
.Set<E>
edges()
Returns all edges in this network, in the order specified byedgeOrder()
.Set<E>
edgesConnecting(EndpointPair<N> endpoints)
Returns the set of edges that each directly connectendpoints
(in the order, if any, specified byendpoints
).Set<E>
edgesConnecting(N nodeU, N nodeV)
Returns the set of edges that each directly connectnodeU
tonodeV
.boolean
equals(@Nullable Object object)
Returnstrue
iffobject
is aNetwork
that has the same elements and the same structural relationships as those in this network.boolean
hasEdgeConnecting(EndpointPair<N> endpoints)
Returns true if there is an edge that directly connectsendpoints
(in the order, if any, specified byendpoints
).boolean
hasEdgeConnecting(N nodeU, N nodeV)
Returns true if there is an edge that directly connectsnodeU
tonodeV
.int
hashCode()
Returns the hash code for this network.Set<E>
incidentEdges(N node)
Returns the edges whoseincident nodes
in this network includenode
.EndpointPair<N>
incidentNodes(E edge)
Returns the nodes which are the endpoints ofedge
in this network.int
inDegree(N node)
Returns the count ofnode
'sincoming edges
in a directed network.Set<E>
inEdges(N node)
Returns all edges in this network which can be traversed in the direction (if any) of the edge to end atnode
.boolean
isDirected()
Returns true if the edges in this network are directed.ElementOrder<N>
nodeOrder()
Returns the order of iteration for the elements ofnodes()
.Set<N>
nodes()
Returns all nodes in this network, in the order specified bynodeOrder()
.int
outDegree(N node)
Returns the count ofnode
'soutgoing edges
in a directed network.Set<E>
outEdges(N node)
Returns all edges in this network which can be traversed in the direction (if any) of the edge starting fromnode
.Set<N>
predecessors(N node)
Returns all nodes in this network adjacent tonode
which can be reached by traversingnode
's incoming edges against the direction (if any) of the edge.Set<N>
successors(N node)
Returns all nodes in this network adjacent tonode
which can be reached by traversingnode
's outgoing edges in the direction (if any) of the edge.



Method Detail

nodes
Set<N> nodes()
Returns all nodes in this network, in the order specified bynodeOrder()
.

edges
Set<E> edges()
Returns all edges in this network, in the order specified byedgeOrder()
.

asGraph
Graph<N> asGraph()
Returns a live view of this network as aGraph
. The resultingGraph
will have an edge connecting node A to node B if thisNetwork
has an edge connecting A to B.If this network
allows parallel edges
, parallel edges will be treated as if collapsed into a single edge. For example, thedegree(Object)
of a node in theGraph
view may be less than the degree of the same node in thisNetwork
.

isDirected
boolean isDirected()
Returns true if the edges in this network are directed. Directed edges connect asource node
to atarget node
, while undirected edges connect a pair of nodes to each other.

allowsParallelEdges
boolean allowsParallelEdges()
Returns true if this network allows parallel edges. Attempting to add a parallel edge to a network that does not allow them will throw anIllegalArgumentException
.

allowsSelfLoops
boolean allowsSelfLoops()
Returns true if this network allows selfloops (edges that connect a node to itself). Attempting to add a selfloop to a network that does not allow them will throw anIllegalArgumentException
.

nodeOrder
ElementOrder<N> nodeOrder()
Returns the order of iteration for the elements ofnodes()
.

edgeOrder
ElementOrder<E> edgeOrder()
Returns the order of iteration for the elements ofedges()
.

adjacentNodes
Set<N> adjacentNodes(N node)
Returns the nodes which have an incident edge in common withnode
in this network.This is equal to the union of
predecessors(Object)
andsuccessors(Object)
. Throws:
IllegalArgumentException
 ifnode
is not an element of this network

predecessors
Set<N> predecessors(N node)
Returns all nodes in this network adjacent tonode
which can be reached by traversingnode
's incoming edges against the direction (if any) of the edge.In an undirected network, this is equivalent to
adjacentNodes(Object)
. Specified by:
predecessors
in interfacePredecessorsFunction<N>
 Throws:
IllegalArgumentException
 ifnode
is not an element of this network

successors
Set<N> successors(N node)
Returns all nodes in this network adjacent tonode
which can be reached by traversingnode
's outgoing edges in the direction (if any) of the edge.In an undirected network, this is equivalent to
adjacentNodes(Object)
.This is not the same as "all nodes reachable from
node
by following outgoing edges". For that functionality, seeGraphs.reachableNodes(Graph, Object)
. Specified by:
successors
in interfaceSuccessorsFunction<N>
 Throws:
IllegalArgumentException
 ifnode
is not an element of this network

incidentEdges
Set<E> incidentEdges(N node)
Returns the edges whoseincident nodes
in this network includenode
.This is equal to the union of
inEdges(Object)
andoutEdges(Object)
. Throws:
IllegalArgumentException
 ifnode
is not an element of this network

inEdges
Set<E> inEdges(N node)
Returns all edges in this network which can be traversed in the direction (if any) of the edge to end atnode
.In a directed network, an incoming edge's
EndpointPair.target()
equalsnode
.In an undirected network, this is equivalent to
incidentEdges(Object)
. Throws:
IllegalArgumentException
 ifnode
is not an element of this network

outEdges
Set<E> outEdges(N node)
Returns all edges in this network which can be traversed in the direction (if any) of the edge starting fromnode
.In a directed network, an outgoing edge's
EndpointPair.source()
equalsnode
.In an undirected network, this is equivalent to
incidentEdges(Object)
. Throws:
IllegalArgumentException
 ifnode
is not an element of this network

degree
int degree(N node)
Returns the count ofnode
'sincident edges
, counting selfloops twice (equivalently, the number of times an edge touchesnode
).For directed networks, this is equal to
inDegree(node) + outDegree(node)
.For undirected networks, this is equal to
incidentEdges(node).size()
+ (number of selfloops incident tonode
).If the count is greater than
Integer.MAX_VALUE
, returnsInteger.MAX_VALUE
. Throws:
IllegalArgumentException
 ifnode
is not an element of this network

inDegree
int inDegree(N node)
Returns the count ofnode
'sincoming edges
in a directed network. In an undirected network, returns thedegree(Object)
.If the count is greater than
Integer.MAX_VALUE
, returnsInteger.MAX_VALUE
. Throws:
IllegalArgumentException
 ifnode
is not an element of this network

outDegree
int outDegree(N node)
Returns the count ofnode
'soutgoing edges
in a directed network. In an undirected network, returns thedegree(Object)
.If the count is greater than
Integer.MAX_VALUE
, returnsInteger.MAX_VALUE
. Throws:
IllegalArgumentException
 ifnode
is not an element of this network

incidentNodes
EndpointPair<N> incidentNodes(E edge)
Returns the nodes which are the endpoints ofedge
in this network. Throws:
IllegalArgumentException
 ifedge
is not an element of this network

adjacentEdges
Set<E> adjacentEdges(E edge)
Returns the edges which have anincident node
in common withedge
. An edge is not considered adjacent to itself. Throws:
IllegalArgumentException
 ifedge
is not an element of this network

edgesConnecting
Set<E> edgesConnecting(N nodeU, N nodeV)
Returns the set of edges that each directly connectnodeU
tonodeV
.In an undirected network, this is equal to
edgesConnecting(nodeV, nodeU)
.The resulting set of edges will be parallel (i.e. have equal
incidentNodes(Object)
. If this network does notallow parallel edges
, the resulting set will contain at most one edge (equivalent toedgeConnecting(nodeU, nodeV).asSet()
). Throws:
IllegalArgumentException
 ifnodeU
ornodeV
is not an element of this network

edgesConnecting
Set<E> edgesConnecting(EndpointPair<N> endpoints)
Returns the set of edges that each directly connectendpoints
(in the order, if any, specified byendpoints
).The resulting set of edges will be parallel (i.e. have equal
incidentNodes(Object)
. If this network does notallow parallel edges
, the resulting set will contain at most one edge (equivalent toedgeConnecting(endpoints).asSet()
).If this network is directed,
endpoints
must be ordered. Throws:
IllegalArgumentException
 if either endpoint is not an element of this networkIllegalArgumentException
 if the endpoints are unordered and the graph is directed Since:
 27.1

edgeConnecting
Optional<E> edgeConnecting(N nodeU, N nodeV)
Returns the single edge that directly connectsnodeU
tonodeV
, if one is present, orOptional.empty()
if no such edge exists.In an undirected network, this is equal to
edgeConnecting(nodeV, nodeU)
. Throws:
IllegalArgumentException
 if there are multiple parallel edges connectingnodeU
tonodeV
IllegalArgumentException
 ifnodeU
ornodeV
is not an element of this network Since:
 23.0

edgeConnecting
Optional<E> edgeConnecting(EndpointPair<N> endpoints)
Returns the single edge that directly connectsendpoints
(in the order, if any, specified byendpoints
), if one is present, orOptional.empty()
if no such edge exists.If this graph is directed, the endpoints must be ordered.
 Throws:
IllegalArgumentException
 if there are multiple parallel edges connectingnodeU
tonodeV
IllegalArgumentException
 if either endpoint is not an element of this networkIllegalArgumentException
 if the endpoints are unordered and the graph is directed Since:
 27.1

edgeConnectingOrNull
@Nullable E edgeConnectingOrNull(N nodeU, N nodeV)
Returns the single edge that directly connectsnodeU
tonodeV
, if one is present, ornull
if no such edge exists.In an undirected network, this is equal to
edgeConnectingOrNull(nodeV, nodeU)
. Throws:
IllegalArgumentException
 if there are multiple parallel edges connectingnodeU
tonodeV
IllegalArgumentException
 ifnodeU
ornodeV
is not an element of this network Since:
 23.0

edgeConnectingOrNull
@Nullable E edgeConnectingOrNull(EndpointPair<N> endpoints)
Returns the single edge that directly connectsendpoints
(in the order, if any, specified byendpoints
), if one is present, ornull
if no such edge exists.If this graph is directed, the endpoints must be ordered.
 Throws:
IllegalArgumentException
 if there are multiple parallel edges connectingnodeU
tonodeV
IllegalArgumentException
 if either endpoint is not an element of this networkIllegalArgumentException
 if the endpoints are unordered and the graph is directed Since:
 27.1

hasEdgeConnecting
boolean hasEdgeConnecting(N nodeU, N nodeV)
Returns true if there is an edge that directly connectsnodeU
tonodeV
. This is equivalent tonodes().contains(nodeU) && successors(nodeU).contains(nodeV)
, and toedgeConnectingOrNull(nodeU, nodeV) != null
.In an undirected graph, this is equal to
hasEdgeConnecting(nodeV, nodeU)
. Since:
 23.0

hasEdgeConnecting
boolean hasEdgeConnecting(EndpointPair<N> endpoints)
Returns true if there is an edge that directly connectsendpoints
(in the order, if any, specified byendpoints
).Unlike the other
EndpointPair
accepting methods, this method does not throw if the endpoints are unordered and the graph is directed; it simply returnsfalse
. This is for consistency withGraph.hasEdgeConnecting(EndpointPair)
andValueGraph.hasEdgeConnecting(EndpointPair)
. Since:
 27.1

equals
boolean equals(@Nullable Object object)
Returnstrue
iffobject
is aNetwork
that has the same elements and the same structural relationships as those in this network.Thus, two networks A and B are equal if all of the following are true:
 A and B have equal
directedness
.  A and B have equal
node sets
.  A and B have equal
edge sets
.  Every edge in A and B connects the same nodes in the same direction (if any).
Network properties besides
directedness
do not affect equality. For example, two networks may be considered equal even if one allows parallel edges and the other doesn't. Additionally, the order in which nodes or edges are added to the network, and the order in which they are iterated over, are irrelevant.A reference implementation of this is provided by
AbstractNetwork.equals(Object)
. Overrides:
equals
in classObject
 Parameters:
object
 the reference object with which to compare. Returns:
true
if this object is the same as the obj argument;false
otherwise. See Also:
Object.hashCode()
,HashMap
 A and B have equal

hashCode
int hashCode()
Returns the hash code for this network. The hash code of a network is defined as the hash code of a map from each of itsedges
to theirincident nodes
.A reference implementation of this is provided by
AbstractNetwork.hashCode()
. Overrides:
hashCode
in classObject
 Returns:
 a hash code value for this object.
 See Also:
Object.equals(java.lang.Object)
,System.identityHashCode(java.lang.Object)

