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 @DoNotMock("Use NetworkBuilder to create a real instance") 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 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

    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 graph 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).
    @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 graph are directed.
    ElementOrder<N>
    nodeOrder()
    Returns the order of iteration for the elements of nodes().
    Set<N>
    nodes()
    Returns all nodes in this graph, 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 graph 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 graph adjacent to node which can be reached by traversing node's outgoing edges in the direction (if any) of the edge.

  • Method Details

    • 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.

    • 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.

    • edgeOrder

      ElementOrder<E> edgeOrder()
      Returns the order of iteration for the elements of edges().

    • 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

    • 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

    • nodes

      Set<N> nodes()
      Returns all nodes in this graph, in the order specified by nodeOrder().

    • isDirected

      boolean isDirected()
      Returns true if the edges in this graph are directed. Directed edges connect a source node to a target node, while undirected edges connect a pair of nodes to each other.

    • allowsSelfLoops

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

    • nodeOrder

      ElementOrder<N> nodeOrder()
      Returns the order of iteration for the elements of nodes().

    • 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 PredecessorsFunction.predecessors(Object) and SuccessorsFunction.successors(Object).

      If node is removed from the graph 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 graph after having been removed, view's behavior is undefined
      Throws:
      IllegalArgumentException - if node is not an element of this graph

    • predecessors

      Set<N> predecessors(N node)
      Returns a live view of all nodes in this graph adjacent to node which can be reached by traversing node's incoming edges against the direction (if any) of the edge.

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

      If node is removed from the graph 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 graph after having been removed, view's behavior is undefined
      Specified by:
      predecessors in interface PredecessorsFunction<N>
      Throws:
      IllegalArgumentException - if node is not an element of this graph

    • successors

      Set<N> successors(N node)
      Returns a live view of all nodes in this graph adjacent to node which can be reached by traversing node's outgoing edges in the direction (if any) of the edge.

      In an undirected graph, 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 graph 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 graph 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 graph