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
@DoNotMock("Use NetworkBuilder to create a real instance")
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> network = 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 network (e.g. if you write a method than runs a read-only algorithm on the network), 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(network);
 
```
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:
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 a live view of the edges which have an `incident node` in common with `edge`.
`Set<N>`	`adjacentNodes(N node)`	Returns a live view of the nodes which have an incident edge in common with `node` in this graph.
`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(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.
`@Nullable 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.
`@Nullable 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 a live view of 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 a live view of 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 a live view of 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 a live view of 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 a live view of 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 a live view of 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 a live view of 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 a live view of the nodes which have an incident edge in common with node in this graph.
    This is equal to the union of predecessors(Object) and successors(Object).
    If node is removed from the network after this method is called, the Set view returned by this method will be invalidated, and will throw IllegalStateException if it is accessed in any way, with the following exceptions:
    
    view.equals(view) evaluates to true (but any other equals() expression involving view will throw)
    hashCode() does not throw
    if node is re-added to the network after having been removed, view's behavior is undefined
    Throws:
    
    IllegalArgumentException - if node is not an element of this network
  - predecessors
```
Set<N> predecessors(N node)
```
    Returns a live view of 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).
    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 interface PredecessorsFunction<N>
    
    Throws:
    
    IllegalArgumentException - if node is not an element of this network
  - successors
```
Set<N> successors(N node)
```
    Returns a live view of 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).
    If node is removed from the network after this method is called, the Set view returned by this method will be invalidated, and will throw IllegalStateException if it is accessed in any way, with the following exceptions:
    
    view.equals(view) evaluates to true (but any other equals() expression involving view will throw)
    hashCode() does not throw
    if node is re-added to the network after having been removed, view's behavior is undefined
    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 a live view of the edges whose incident nodes in this network include node.
    This is equal to the union of inEdges(Object) and outEdges(Object).
    If node is removed from the network after this method is called, the Set view returned by this method will be invalidated, and will throw IllegalStateException if it is accessed in any way, with the following exceptions:
    
    view.equals(view) evaluates to true (but any other equals() expression involving view will throw)
    hashCode() does not throw
    if node is re-added to the network after having been removed, view's behavior is undefined
    Throws:
    
    IllegalArgumentException - if node is not an element of this network
    
    Since:
    
    24.0
  - inEdges
```
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 at node.
    In a directed network, an incoming edge's EndpointPair.target() equals node.
    In an undirected network, this is equivalent to incidentEdges(Object).
    If node is removed from the network after this method is called, the Set view returned by this method will be invalidated, and will throw IllegalStateException if it is accessed in any way, with the following exceptions:
    
    view.equals(view) evaluates to true (but any other equals() expression involving view will throw)
    hashCode() does not throw
    if node is re-added to the network after having been removed, view's behavior is undefined
    Throws:
    
    IllegalArgumentException - if node is not an element of this network
  - outEdges
```
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 from node.
    In a directed network, an outgoing edge's EndpointPair.source() equals node.
    In an undirected network, this is equivalent to incidentEdges(Object).
    If node is removed from the network after this method is called, the Set view returned by this method will be invalidated, and will throw IllegalStateException if it is accessed in any way, with the following exceptions:
    
    view.equals(view) evaluates to true (but any other equals() expression involving view will throw)
    hashCode() does not throw
    if node is re-added to the network after having been removed, view's behavior is undefined
    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 a live view of the edges which have an incident node in common with edge. An edge is not considered adjacent to itself.
    If edge is removed from the network after this method is called, the Set view returned by this method will be invalidated, and will throw IllegalStateException if it is accessed in any way, with the following exceptions:
    
    view.equals(view) evaluates to true (but any other equals() expression involving view will throw)
    hashCode() does not throw
    if edge is re-added to the network after having been removed, view's behavior is undefined
    Throws:
    
    IllegalArgumentException - if edge is not an element of this network
  - edgesConnecting
```
Set<E> edgesConnecting(N nodeU,
                       N nodeV)
```
    Returns a live view of the set of edges that each directly connect 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()).
    If either nodeU or nodeV are removed from the network after this method is called, the Set view returned by this method will be invalidated, and will throw IllegalStateException if it is accessed in any way, with the following exceptions:
    
    view.equals(view) evaluates to true (but any other equals() expression involving view will throw)
    hashCode() does not throw
    if nodeU or nodeV are re-added to the network after having been removed, view's behavior is undefined
    Throws:
    
    IllegalArgumentException - if nodeU or nodeV is not an element of this network
  - edgesConnecting
```
Set<E> edgesConnecting(EndpointPair<N> endpoints)
```
    Returns a live view of the set of edges that each directly connect 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.
    If either element of endpoints is removed from the network after this method is called, the Set view returned by this method will be invalidated, and will throw IllegalStateException if it is accessed in any way, with the following exceptions:
    
    view.equals(view) evaluates to true (but any other equals() expression involving view will throw)
    hashCode() does not throw
    if either endpoint is re-added to the network after having been removed, view's behavior is undefined
    Throws:
    
    IllegalArgumentException - if either endpoint is not an element of this network
    
    IllegalArgumentException - if the endpoints are unordered and the network is directed
    
    Since:
    
    27.1
  - edgeConnecting
```
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.
    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
  - edgeConnecting
```
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.
    If this network is directed, the endpoints must be ordered.
    
    Throws:
    
    IllegalArgumentException - if there are multiple parallel edges connecting nodeU to nodeV
    
    IllegalArgumentException - if either endpoint is not an element of this network
    
    IllegalArgumentException - if the endpoints are unordered and the network is directed
    
    Since:
    
    27.1
  - edgeConnectingOrNull
```
@Nullable 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.
    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
  - edgeConnectingOrNull
```
@Nullable 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.
    If this network is directed, the endpoints must be ordered.
    
    Throws:
    
    IllegalArgumentException - if there are multiple parallel edges connecting nodeU to nodeV
    
    IllegalArgumentException - if either endpoint is not an element of this network
    
    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 connects nodeU to nodeV. This is equivalent to nodes().contains(nodeU) && successors(nodeU).contains(nodeV), and to edgeConnectingOrNull(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 connects 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 network is directed; it simply returns false. This is for consistency with Graph.hasEdgeConnecting(EndpointPair) and ValueGraph.hasEdgeConnecting(EndpointPair).
    
    Since:
    
    27.1
  - 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
  - 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

Interface Network<N,E>

Capabilities

Building a `Network`

Additional documentation

Method Summary

Method Detail

nodes

edges

asGraph

isDirected

allowsParallelEdges

allowsSelfLoops

nodeOrder

edgeOrder

adjacentNodes

predecessors

successors

incidentEdges

inEdges

outEdges

degree

inDegree

outDegree

incidentNodes

adjacentEdges

edgesConnecting

edgesConnecting

edgeConnecting

edgeConnecting

edgeConnectingOrNull

edgeConnectingOrNull

hasEdgeConnecting

hasEdgeConnecting

equals

hashCode

Interface Network<N,​E>

Capabilities

Building a Network

Additional documentation

Method Summary

Method Detail

nodes

edges

asGraph

isDirected

allowsParallelEdges

allowsSelfLoops

nodeOrder

edgeOrder

adjacentNodes

predecessors

successors

incidentEdges

inEdges

outEdges

degree

inDegree

outDegree

incidentNodes

adjacentEdges

edgesConnecting

edgesConnecting

edgeConnecting

edgeConnecting

edgeConnectingOrNull

edgeConnectingOrNull

hasEdgeConnecting

hasEdgeConnecting

equals

hashCode

Interface Network<N,E>

Building a `Network`