com.google.common.graph

Interface Network<N,E>

Type Parameters:

N - Node parameter type

E - Edge parameter type

All Superinterfaces:

PredecessorsFunction<N>, SuccessorsFunction<N>

All Known Subinterfaces:

MutableNetwork<N,E>

All Known Implementing Classes:

AbstractNetwork, ImmutableNetwork

@Beta
public interface Network<N,E>
extends SuccessorsFunction<N>, PredecessorsFunction<N>

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 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.

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(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 self-loops (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 self-loops twice (equivalently, the number of times an edge touches node).
Optional<E>	edgeConnecting(N nodeU, N nodeV) Returns the single edge directly connecting nodeU to nodeV, if one is present, or Optional.empty() if no such edge exists.
E	edgeConnectingOrNull(N nodeU, N nodeV) Returns the single edge directly connecting 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(N nodeU, N nodeV) Returns the set of edges directly connecting nodeU to nodeV.
boolean	equals(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(N nodeU, N nodeV) Returns true if there is an edge directly connecting 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.

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 IllegalArgumentException.

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 IllegalArgumentException.

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(N 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(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.

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

Specified by:

predecessors in interface PredecessorsFunction<N>

Throws:

IllegalArgumentException - if node is not an element of this network

successors

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.

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).

Specified by:

successors in interface SuccessorsFunction<N>

Throws:

IllegalArgumentException - if node is not an element of this network

incidentEdges

Set<E> incidentEdges(N 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(N 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(N 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(N 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(N 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(N 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(E 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(E 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(N nodeU,
                       N 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 (equivalent to edgeConnecting(nodeU, nodeV).asSet()).

Throws:

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

edgeConnecting

Optional<E> edgeConnecting(N nodeU,
                           N nodeV)

Returns the single edge directly connecting 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).

Throws:

IllegalArgumentException - if there are multiple parallel edges connecting nodeU to nodeV

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

Since:

23.0

edgeConnectingOrNull

@Nullable
E edgeConnectingOrNull(N nodeU,
                                 N nodeV)

Returns the single edge directly connecting 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).

Throws:

IllegalArgumentException - if there are multiple parallel edges connecting nodeU to nodeV

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

Since:

23.0

hasEdgeConnecting

boolean hasEdgeConnecting(N nodeU,
                          N nodeV)

Returns true if there is an edge directly connecting 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).

Since:

23.0

equals

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.

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 class Object

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

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 its edges to their incident nodes.

A reference implementation of this is provided by AbstractNetwork.hashCode().

Overrides:

hashCode in class Object

Returns:

a hash code value for this object.

See Also:

Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)