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> network = 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 network (e.g. if you write a method than runs a readonly algorithm on the network), 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(network);
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 java.util.Set<E>
adjacentEdges(E edge)
Returns a live view of the edges which have anincident node
in common withedge
.java.util.Set<N>
adjacentNodes(N node)
Returns a live view of the nodes which have an incident edge in common withnode
in this graph.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
).java.util.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.java.util.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.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.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()
.java.util.Set<E>
edges()
Returns all edges in this network, in the order specified byedgeOrder()
.java.util.Set<E>
edgesConnecting(EndpointPair<N> endpoints)
Returns a live view of the set of edges that each directly connectendpoints
(in the order, if any, specified byendpoints
).java.util.Set<E>
edgesConnecting(N nodeU, N nodeV)
Returns a live view of the set of edges that each directly connectnodeU
tonodeV
.boolean
equals(java.lang.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.java.util.Set<E>
incidentEdges(N node)
Returns a live view of 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.java.util.Set<E>
inEdges(N node)
Returns a live view of 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()
.java.util.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.java.util.Set<E>
outEdges(N node)
Returns a live view of all edges in this network which can be traversed in the direction (if any) of the edge starting fromnode
.java.util.Set<N>
predecessors(N node)
Returns a live view of all nodes in this network adjacent tonode
which can be reached by traversingnode
's incoming edges against the direction (if any) of the edge.java.util.Set<N>
successors(N node)
Returns a live view of 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
java.util.Set<N> nodes()
Returns all nodes in this network, in the order specified bynodeOrder()
.

edges
java.util.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
java.util.Set<N> adjacentNodes(N node)
Returns a live view of the nodes which have an incident edge in common withnode
in this graph.This is equal to the union of
predecessors(Object)
andsuccessors(Object)
.If
node
is removed from the network after this method is called, theSet
view
returned by this method will be invalidated, and will throwIllegalStateException
if it is accessed in any way, with the following exceptions:view.equals(view)
evaluates totrue
(but any other `equals()` expression involvingview
will throw)hashCode()
does not throw if
node
is readded to the network after having been removed,view
's behavior is undefined
 Throws:
java.lang.IllegalArgumentException
 ifnode
is not an element of this network

predecessors
java.util.Set<N> predecessors(N node)
Returns a live view of 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)
.If
node
is removed from the network after this method is called, the `Set` returned by this method will be invalidated, and will throw `IllegalStateException` if it is accessed in any way. Specified by:
predecessors
in interfacePredecessorsFunction<N>
 Throws:
java.lang.IllegalArgumentException
 ifnode
is not an element of this network

successors
java.util.Set<N> successors(N node)
Returns a live view of 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)
.If
node
is removed from the network after this method is called, theSet
view
returned by this method will be invalidated, and will throwIllegalStateException
if it is accessed in any way, with the following exceptions:view.equals(view)
evaluates totrue
(but any other `equals()` expression involvingview
will throw)hashCode()
does not throw if
node
is readded to the network after having been removed,view
's behavior is undefined
 Specified by:
successors
in interfaceSuccessorsFunction<N>
 Throws:
java.lang.IllegalArgumentException
 ifnode
is not an element of this network

incidentEdges
java.util.Set<E> incidentEdges(N node)
Returns a live view of the edges whoseincident nodes
in this network includenode
.This is equal to the union of
inEdges(Object)
andoutEdges(Object)
.If
node
is removed from the network after this method is called, theSet
view
returned by this method will be invalidated, and will throwIllegalStateException
if it is accessed in any way, with the following exceptions:view.equals(view)
evaluates totrue
(but any other `equals()` expression involvingview
will throw)hashCode()
does not throw if
node
is readded to the network after having been removed,view
's behavior is undefined
 Throws:
java.lang.IllegalArgumentException
 ifnode
is not an element of this network Since:
 24.0

inEdges
java.util.Set<E> inEdges(N node)
Returns a live view of 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)
.If
node
is removed from the network after this method is called, theSet
view
returned by this method will be invalidated, and will throwIllegalStateException
if it is accessed in any way, with the following exceptions:view.equals(view)
evaluates totrue
(but any other `equals()` expression involvingview
will throw)hashCode()
does not throw if
node
is readded to the network after having been removed,view
's behavior is undefined
 Throws:
java.lang.IllegalArgumentException
 ifnode
is not an element of this network

outEdges
java.util.Set<E> outEdges(N node)
Returns a live view of 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)
.If
node
is removed from the network after this method is called, theSet
view
returned by this method will be invalidated, and will throwIllegalStateException
if it is accessed in any way, with the following exceptions:view.equals(view)
evaluates totrue
(but any other `equals()` expression involvingview
will throw)hashCode()
does not throw if
node
is readded to the network after having been removed,view
's behavior is undefined
 Throws:
java.lang.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:
java.lang.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:
java.lang.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:
java.lang.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:
java.lang.IllegalArgumentException
 ifedge
is not an element of this network

adjacentEdges
java.util.Set<E> adjacentEdges(E edge)
Returns a live view of the edges which have anincident node
in common withedge
. An edge is not considered adjacent to itself.If
edge
is removed from the network after this method is called, theSet
view
returned by this method will be invalidated, and will throwIllegalStateException
if it is accessed in any way, with the following exceptions:view.equals(view)
evaluates totrue
(but any other `equals()` expression involvingview
will throw)hashCode()
does not throw if
edge
is readded to the network after having been removed,view
's behavior is undefined
 Throws:
java.lang.IllegalArgumentException
 ifedge
is not an element of this network

edgesConnecting
java.util.Set<E> edgesConnecting(N nodeU, N nodeV)
Returns a live view of 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()
).If either
nodeU
ornodeV
are removed from the network after this method is called, theSet
view
returned by this method will be invalidated, and will throwIllegalStateException
if it is accessed in any way, with the following exceptions:view.equals(view)
evaluates totrue
(but any other `equals()` expression involvingview
will throw)hashCode()
does not throw if
nodeU
ornodeV
are readded to the network after having been removed,view
's behavior is undefined
 Throws:
java.lang.IllegalArgumentException
 ifnodeU
ornodeV
is not an element of this network

edgesConnecting
java.util.Set<E> edgesConnecting(EndpointPair<N> endpoints)
Returns a live view of 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.If either element of
endpoints
is removed from the network after this method is called, theSet
view
returned by this method will be invalidated, and will throwIllegalStateException
if it is accessed in any way, with the following exceptions:view.equals(view)
evaluates totrue
(but any other `equals()` expression involvingview
will throw)hashCode()
does not throw if either endpoint is readded to the network after having been removed,
view
's behavior is undefined
 Throws:
java.lang.IllegalArgumentException
 if either endpoint is not an element of this networkjava.lang.IllegalArgumentException
 if the endpoints are unordered and the network is directed Since:
 27.1

edgeConnecting
java.util.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:
java.lang.IllegalArgumentException
 if there are multiple parallel edges connectingnodeU
tonodeV
java.lang.IllegalArgumentException
 ifnodeU
ornodeV
is not an element of this network Since:
 23.0

edgeConnecting
java.util.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 network is directed, the endpoints must be ordered.
 Throws:
java.lang.IllegalArgumentException
 if there are multiple parallel edges connectingnodeU
tonodeV
java.lang.IllegalArgumentException
 if either endpoint is not an element of this networkjava.lang.IllegalArgumentException
 if the endpoints are unordered and the network is directed Since:
 27.1

edgeConnectingOrNull
@CheckForNull 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:
java.lang.IllegalArgumentException
 if there are multiple parallel edges connectingnodeU
tonodeV
java.lang.IllegalArgumentException
 ifnodeU
ornodeV
is not an element of this network Since:
 23.0

edgeConnectingOrNull
@CheckForNull 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 network is directed, the endpoints must be ordered.
 Throws:
java.lang.IllegalArgumentException
 if there are multiple parallel edges connectingnodeU
tonodeV
java.lang.IllegalArgumentException
 if either endpoint is not an element of this networkjava.lang.IllegalArgumentException
 if the endpoints are unordered and the network 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 network, 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 network is directed; it simply returnsfalse
. This is for consistency withGraph.hasEdgeConnecting(EndpointPair)
andValueGraph.hasEdgeConnecting(EndpointPair)
. Since:
 27.1

equals
boolean equals(@CheckForNull java.lang.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 classjava.lang.Object
 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 classjava.lang.Object

