com.google.common.graph

Interface Network<N,E>

Type Parameters:

N - Node parameter type

E - Edge parameter type

All Known Subinterfaces:

MutableNetwork<N,E>

All Known Implementing Classes:

AbstractNetwork, ImmutableNetwork

@Beta
public interface Network<N,E>

An interface for graph-structured 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 main 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.

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 self-loops
• graphs whose nodes/edges are insertion-ordered, 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 built-in 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 read-only algorithm on the graph), you should use the non-mutating 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 thread-safe.

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:

• equals(), hashCode(), and graph equivalence
• Synchronization policy
• Notes for implementors

Since:

20.0

Author:

James Sexton, Joshua O'Madadhain

Method Summary

Modifier and Type	Method and Description
Set<E>	adjacentEdges(Object edge) Returns the edges which have an incident node in common with edge.
Set<N>	adjacentNodes(Object 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 self-loops (edges that connect a node to itself).
Graph<N>	asGraph() Returns a live view of this network as a Graph.
int	degree(Object node) Returns the count of node's incident edges, counting self-loops twice (equivalently, the number of times an edge touches node).
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(Object nodeU, Object nodeV) Returns the set of edges directly connecting nodeU to nodeV.
boolean	equals(Object object) For the default Network implementations, returns true if this == object (reference equality).
int	hashCode() For the default Network implementations, returns System.identityHashCode(this).
Set<E>	incidentEdges(Object node) Returns the edges whose incident nodes in this network include node.
EndpointPair<N>	incidentNodes(Object edge) Returns the nodes which are the endpoints of edge in this network.
int	inDegree(Object node) Returns the count of node's incoming edges in a directed network.
Set<E>	inEdges(Object 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(Object node) Returns the count of node's outgoing edges in a directed network.
Set<E>	outEdges(Object 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(Object 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(Object 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.

Method Detail

nodes

Set<N> nodes()

Returns all nodes in this network, in the order specified by nodeOrder().

edges

Set<E> edges()

Returns all edges in this network, in the order specified by edgeOrder().

asGraph

Graph<N> asGraph()

Returns a live view of this network as a 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.

isDirected

boolean isDirected()

Returns true if the edges in this network are directed. Directed edges connect a source node to a target 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 an UnsupportedOperationException.

allowsSelfLoops

boolean allowsSelfLoops()

Returns true if this network allows self-loops (edges that connect a node to itself). Attempting to add a self-loop to a network that does not allow them will throw an UnsupportedOperationException.

nodeOrder

ElementOrder<N> nodeOrder()

Returns the order of iteration for the elements of nodes().

edgeOrder

ElementOrder<E> edgeOrder()

Returns the order of iteration for the elements of edges().

adjacentNodes

Set<N> adjacentNodes(Object node)

Returns the nodes which have an incident edge in common with node in this network.

Throws:

IllegalArgumentException - if node is not an element of this network

predecessors

Set<N> predecessors(Object 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.

In an undirected network, this is equivalent to adjacentNodes(Object).

Throws:

IllegalArgumentException - if node is not an element of this network

successors

Set<N> successors(Object 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.

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).

Throws:

IllegalArgumentException - if node is not an element of this network

incidentEdges

Set<E> incidentEdges(Object node)

Returns the edges whose incident nodes in this network include node.

Throws:

IllegalArgumentException - if node is not an element of this network

inEdges

Set<E> inEdges(Object node)

Returns all edges in this network which can be traversed in the direction (if any) of the edge to end at node.

In a directed network, an incoming edge's EndpointPair.target() equals node.

In an undirected network, this is equivalent to incidentEdges(Object).

Throws:

IllegalArgumentException - if node is not an element of this network

outEdges

Set<E> outEdges(Object node)

Returns all edges in this network which can be traversed in the direction (if any) of the edge starting from node.

In a directed network, an outgoing edge's EndpointPair.source() equals node.

In an undirected network, this is equivalent to incidentEdges(Object).

Throws:

IllegalArgumentException - if node is not an element of this network

degree

int degree(Object node)

Returns the count of node's incident edges, counting self-loops 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 self-loops incident to node).

If the count is greater than Integer.MAX_VALUE, returns Integer.MAX_VALUE.

Throws:

IllegalArgumentException - if node is not an element of this network

inDegree

int inDegree(Object node)

Returns the count of 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.

Throws:

IllegalArgumentException - if node is not an element of this network

outDegree

int outDegree(Object node)

Returns the count of 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.

Throws:

IllegalArgumentException - if node is not an element of this network

incidentNodes

EndpointPair<N> incidentNodes(Object edge)

Returns the nodes which are the endpoints of edge in this network.

Throws:

IllegalArgumentException - if edge is not an element of this network

adjacentEdges

Set<E> adjacentEdges(Object edge)

Returns the edges which have an incident node in common with edge. An edge is not considered adjacent to itself.

Throws:

IllegalArgumentException - if edge is not an element of this network

edgesConnecting

Set<E> edgesConnecting(Object nodeU,
                       Object nodeV)

Returns the set of edges directly connecting 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.

Throws:

IllegalArgumentException - if nodeU or nodeV is not an element of this network

equals

boolean equals(@Nullable
               Object object)

For the default Network implementations, returns true if this == object (reference equality). External implementations are free to define this method as they see fit, as long as they satisfy the Object.equals(Object) contract.

To compare two Networks based on their contents rather than their references, see Graphs.equivalent(Network, Network).

Overrides:

equals in class Object

hashCode

int hashCode()

For the default Network implementations, returns System.identityHashCode(this). External implementations are free to define this method as they see fit, as long as they satisfy the Object.hashCode() contract.

Overrides:

hashCode in class Object