N
 Node parameter typeE
 Edge parameter type@Beta public interface Network<N,E> extends SuccessorsFunction<N>, PredecessorsFunction<N>
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
, and Network
. 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.
Network
supports the following use cases (definitions of
terms):
Network
The implementation classes that common.graph
provides are not public, by design. To
create an instance of one of the builtin implementations of Network
, use the NetworkBuilder
class:
MutableNetwork<Integer, MyEdge> graph = NetworkBuilder.directed().build();
NetworkBuilder.build()
returns an instance of MutableNetwork
, which is a
subtype of Network
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 nonmutating Network
interface, or an ImmutableNetwork
.
You can create an immutable copy of an existing Network
using ImmutableNetwork.copyOf(Network)
:
ImmutableNetwork<Integer, MyEdge> immutableGraph = ImmutableNetwork.copyOf(graph);
Instances of ImmutableNetwork
do not implement MutableNetwork
(obviously!) and
are contractually guaranteed to be unmodifiable and threadsafe.
The Guava User Guide has more information on (and examples of) building graphs.
See the Guava User Guide for the common.graph
package ("Graphs Explained") for
additional documentation, including:
Modifier and Type  Method and Description 

Set<E> 
adjacentEdges(E edge)
Returns the edges which have an
incident node in common with
edge . 
Set<N> 
adjacentNodes(N node)
Returns the nodes which have an incident edge in common with
node 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 a
Graph . 
int 
degree(N node)
Returns the count of
node 's incident edges , counting
selfloops twice (equivalently, the number of times an edge touches node ). 
Optional<E> 
edgeConnecting(EndpointPair<N> endpoints)
Returns the single edge that directly connects
endpoints (in the order, if any,
specified by endpoints ), if one is present, or Optional.empty() if no such edge
exists. 
Optional<E> 
edgeConnecting(N nodeU,
N nodeV)
Returns the single edge that directly connects
nodeU to nodeV , if one is
present, or Optional.empty() if no such edge exists. 
E 
edgeConnectingOrNull(EndpointPair<N> endpoints)
Returns the single edge that directly connects
endpoints (in the order, if any,
specified by endpoints ), if one is present, or null if no such edge exists. 
E 
edgeConnectingOrNull(N nodeU,
N nodeV)
Returns the single edge that directly connects
nodeU to nodeV , if one is
present, or null if no such edge exists. 
ElementOrder<E> 
edgeOrder()
Returns the order of iteration for the elements of
edges() . 
Set<E> 
edges()
Returns all edges in this network, in the order specified by
edgeOrder() . 
Set<E> 
edgesConnecting(EndpointPair<N> endpoints)
Returns the set of edges that each directly connect
endpoints (in the order, if any,
specified by endpoints ). 
Set<E> 
edgesConnecting(N nodeU,
N nodeV)
Returns the set of edges that each directly connect
nodeU to nodeV . 
boolean 
equals(@Nullable Object object)
Returns
true iff object is a Network 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 connects
endpoints (in the order, if
any, specified by endpoints ). 
boolean 
hasEdgeConnecting(N nodeU,
N nodeV)
Returns true if there is an edge that directly connects
nodeU to nodeV . 
int 
hashCode()
Returns the hash code for this network.

Set<E> 
incidentEdges(N node)
Returns the edges whose
incident nodes in this network include
node . 
EndpointPair<N> 
incidentNodes(E edge)
Returns the nodes which are the endpoints of
edge in this network. 
int 
inDegree(N node)
Returns the count of
node 's incoming 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 at
node . 
boolean 
isDirected()
Returns true if the edges in this network are directed.

ElementOrder<N> 
nodeOrder()
Returns the order of iteration for the elements of
nodes() . 
Set<N> 
nodes()
Returns all nodes in this network, in the order specified by
nodeOrder() . 
int 
outDegree(N node)
Returns the count of
node 's outgoing 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 from
node . 
Set<N> 
predecessors(N node)
Returns all nodes in this network adjacent to
node which can be reached by traversing
node 's incoming edges against the direction (if any) of the edge. 
Set<N> 
successors(N node)
Returns all nodes in this network adjacent to
node which can be reached by traversing
node 's outgoing edges in the direction (if any) of the edge. 
Set<N> nodes()
nodeOrder()
.Set<E> edges()
edgeOrder()
.Graph<N> asGraph()
Graph
. The resulting Graph
will have
an edge connecting node A to node B if this Network
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, the degree(Object)
of a node
in the Graph
view may be less than the degree of the same node in this Network
.
boolean isDirected()
source node
to a target node
, while
undirected edges connect a pair of nodes to each other.boolean allowsParallelEdges()
IllegalArgumentException
.boolean allowsSelfLoops()
IllegalArgumentException
.ElementOrder<N> nodeOrder()
nodes()
.ElementOrder<E> edgeOrder()
edges()
.Set<N> adjacentNodes(N node)
node
in this network.
This is equal to the union of predecessors(Object)
and successors(Object)
.
IllegalArgumentException
 if node
is not an element of this networkSet<N> predecessors(N node)
node
which can be reached by traversing
node
's incoming edges against the direction (if any) of the edge.
In an undirected network, this is equivalent to adjacentNodes(Object)
.
predecessors
in interface PredecessorsFunction<N>
IllegalArgumentException
 if node
is not an element of this networkSet<N> successors(N node)
node
which can be reached by traversing
node
'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, see Graphs.reachableNodes(Graph, Object)
.
successors
in interface SuccessorsFunction<N>
IllegalArgumentException
 if node
is not an element of this networkSet<E> incidentEdges(N node)
incident nodes
in this network include
node
.
This is equal to the union of inEdges(Object)
and outEdges(Object)
.
IllegalArgumentException
 if node
is not an element of this networkSet<E> inEdges(N node)
node
.
In a directed network, an incoming edge's EndpointPair.target()
equals node
.
In an undirected network, this is equivalent to incidentEdges(Object)
.
IllegalArgumentException
 if node
is not an element of this networkSet<E> outEdges(N node)
node
.
In a directed network, an outgoing edge's EndpointPair.source()
equals node
.
In an undirected network, this is equivalent to incidentEdges(Object)
.
IllegalArgumentException
 if node
is not an element of this networkint degree(N node)
node
's incident edges
, counting
selfloops twice (equivalently, the number of times an edge touches node
).
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 to node
).
If the count is greater than Integer.MAX_VALUE
, returns Integer.MAX_VALUE
.
IllegalArgumentException
 if node
is not an element of this networkint inDegree(N node)
node
's incoming edges
in a directed
network. In an undirected network, returns the degree(Object)
.
If the count is greater than Integer.MAX_VALUE
, returns Integer.MAX_VALUE
.
IllegalArgumentException
 if node
is not an element of this networkint outDegree(N node)
node
's outgoing edges
in a directed
network. In an undirected network, returns the degree(Object)
.
If the count is greater than Integer.MAX_VALUE
, returns Integer.MAX_VALUE
.
IllegalArgumentException
 if node
is not an element of this networkEndpointPair<N> incidentNodes(E edge)
edge
in this network.IllegalArgumentException
 if edge
is not an element of this networkSet<E> adjacentEdges(E edge)
incident node
in common with
edge
. An edge is not considered adjacent to itself.IllegalArgumentException
 if edge
is not an element of this networkSet<E> edgesConnecting(N nodeU, N nodeV)
nodeU
to nodeV
.
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 not allow parallel edges
, the resulting set
will contain at most one edge (equivalent to edgeConnecting(nodeU, nodeV).asSet()
).
IllegalArgumentException
 if nodeU
or nodeV
is not an element of this
networkSet<E> edgesConnecting(EndpointPair<N> endpoints)
endpoints
(in the order, if any,
specified by endpoints
).
The resulting set of edges will be parallel (i.e. have equal incidentNodes(Object)
.
If this network does not allow parallel edges
, the resulting set
will contain at most one edge (equivalent to edgeConnecting(endpoints).asSet()
).
If this network is directed, endpoints
must be ordered.
IllegalArgumentException
 if either endpoint is not an element of this networkIllegalArgumentException
 if the endpoints are unordered and the graph is directedOptional<E> edgeConnecting(N nodeU, N nodeV)
nodeU
to nodeV
, if one is
present, or Optional.empty()
if no such edge exists.
In an undirected network, this is equal to edgeConnecting(nodeV, nodeU)
.
IllegalArgumentException
 if there are multiple parallel edges connecting nodeU
to nodeV
IllegalArgumentException
 if nodeU
or nodeV
is not an element of this
networkOptional<E> edgeConnecting(EndpointPair<N> endpoints)
endpoints
(in the order, if any,
specified by endpoints
), if one is present, or Optional.empty()
if no such edge
exists.
If this graph is directed, the endpoints must be ordered.
IllegalArgumentException
 if there are multiple parallel edges connecting nodeU
to nodeV
IllegalArgumentException
 if either endpoint is not an element of this networkIllegalArgumentException
 if the endpoints are unordered and the graph is directedE edgeConnectingOrNull(N nodeU, N nodeV)
nodeU
to nodeV
, if one is
present, or null
if no such edge exists.
In an undirected network, this is equal to edgeConnectingOrNull(nodeV, nodeU)
.
IllegalArgumentException
 if there are multiple parallel edges connecting nodeU
to nodeV
IllegalArgumentException
 if nodeU
or nodeV
is not an element of this
networkE edgeConnectingOrNull(EndpointPair<N> endpoints)
endpoints
(in the order, if any,
specified by endpoints
), if one is present, or null
if no such edge exists.
If this graph is directed, the endpoints must be ordered.
IllegalArgumentException
 if there are multiple parallel edges connecting nodeU
to nodeV
IllegalArgumentException
 if either endpoint is not an element of this networkIllegalArgumentException
 if the endpoints are unordered and the graph is directedboolean hasEdgeConnecting(N nodeU, N nodeV)
nodeU
to nodeV
. This is
equivalent to nodes().contains(nodeU) && successors(nodeU).contains(nodeV)
, and to
edgeConnectingOrNull(nodeU, nodeV) != null
.
In an undirected graph, this is equal to hasEdgeConnecting(nodeV, nodeU)
.
boolean hasEdgeConnecting(EndpointPair<N> endpoints)
endpoints
(in the order, if
any, specified by endpoints
).
Unlike the other EndpointPair
accepting methods, this method does not throw if the
endpoints are unordered and the graph is directed; it simply returns false
. This is for
consistency with Graph.hasEdgeConnecting(EndpointPair)
and ValueGraph.hasEdgeConnecting(EndpointPair)
.
boolean equals(@Nullable Object object)
true
iff object
is a Network
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:
directedness
.
node sets
.
edge sets
.
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)
.
int hashCode()
edges
to their incident nodes
.
A reference implementation of this is provided by AbstractNetwork.hashCode()
.
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