Interface Graph<N>
- Type Parameters:
N
- Node parameter type
- All Known Subinterfaces:
MutableGraph<N>
,MutableValueGraph<N,
,V> ValueGraph<N,
V>
- All Known Implementing Classes:
AbstractGraph
,AbstractValueGraph
,ImmutableGraph
,ImmutableValueGraph
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
Graph
supports the following use cases (definitions of
terms):
- directed graphs
- undirected graphs
- graphs that do/don't allow self-loops
- graphs whose nodes/edges are insertion-ordered, sorted, or unordered
Graph
explicitly does not support parallel edges, and forbids implementations or
extensions with parallel edges. If you need parallel edges, use Network
.
Building a Graph
The implementation classes that `common.graph` provides are not public, by design. To create
an instance of one of the built-in implementations of Graph
, use the GraphBuilder
class:
MutableGraph<Integer> graph = GraphBuilder.undirected().build();
GraphBuilder.build()
returns an instance of MutableGraph
, which is a subtype
of Graph
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 Graph
interface, or an ImmutableGraph
.
You can create an immutable copy of an existing Graph
using ImmutableGraph.copyOf(Graph)
:
ImmutableGraph<Integer> immutableGraph = ImmutableGraph.copyOf(graph);
Instances of ImmutableGraph
do not implement MutableGraph
(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
-
Method Summary
Modifier and TypeMethodDescriptionadjacentNodes
(Object node) Returns the nodes which have an incident edge in common withnode
in this graph.boolean
Returns true if this graph allows self-loops (edges that connect a node to itself).int
Returns the count ofnode
's incident edges, counting self-loops twice (equivalently, the number of times an edge touchesnode
).Set
<EndpointPair<N>> edges()
Returns all edges in this graph.boolean
For the defaultGraph
implementations, returns true ifthis == object
(reference equality).int
hashCode()
For the defaultGraph
implementations, returnsSystem.identityHashCode(this)
.int
Returns the count ofnode
's incoming edges (equal topredecessors(node).size()
) in a directed graph.boolean
Returns true if the edges in this graph are directed.Returns the order of iteration for the elements ofnodes()
.nodes()
Returns all nodes in this graph, in the order specified bynodeOrder()
.int
Returns the count ofnode
's outgoing edges (equal tosuccessors(node).size()
) in a directed graph.predecessors
(Object node) Returns all nodes in this graph adjacent tonode
which can be reached by traversingnode
's incoming edges against the direction (if any) of the edge.successors
(Object node) Returns all nodes in this graph adjacent tonode
which can be reached by traversingnode
's outgoing edges in the direction (if any) of the edge.
-
Method Details
-
nodes
Returns all nodes in this graph, in the order specified bynodeOrder()
. -
edges
Set<EndpointPair<N>> edges()Returns all edges in this graph. -
isDirected
boolean isDirected()Returns true if the edges in this graph are directed. Directed edges connect asource node
to atarget 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 anUnsupportedOperationException
. -
nodeOrder
ElementOrder<N> nodeOrder()Returns the order of iteration for the elements ofnodes()
. -
adjacentNodes
Returns the nodes which have an incident edge in common withnode
in this graph.- Throws:
IllegalArgumentException
- ifnode
is not an element of this graph
-
predecessors
Returns all nodes in this graph adjacent tonode
which can be reached by traversingnode
's incoming edges against the direction (if any) of the edge.In an undirected graph, this is equivalent to
adjacentNodes(Object)
.- Throws:
IllegalArgumentException
- ifnode
is not an element of this graph
-
successors
Returns all nodes in this graph adjacent tonode
which can be reached by traversingnode
'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, seeGraphs.reachableNodes(Graph, Object)
.- Throws:
IllegalArgumentException
- ifnode
is not an element of this graph
-
degree
Returns the count ofnode
's incident edges, counting self-loops twice (equivalently, the number of times an edge touchesnode
).For directed graphs, this is equal to
inDegree(node) + outDegree(node)
.For undirected graphs, this is equal to
adjacentNodes(node).size()
+ (1 ifnode
has an incident self-loop, 0 otherwise).If the count is greater than
Integer.MAX_VALUE
, returnsInteger.MAX_VALUE
.- Throws:
IllegalArgumentException
- ifnode
is not an element of this graph
-
inDegree
Returns the count ofnode
's incoming edges (equal topredecessors(node).size()
) in a directed graph. In an undirected graph, returns thedegree(Object)
.If the count is greater than
Integer.MAX_VALUE
, returnsInteger.MAX_VALUE
.- Throws:
IllegalArgumentException
- ifnode
is not an element of this graph
-
outDegree
Returns the count ofnode
's outgoing edges (equal tosuccessors(node).size()
) in a directed graph. In an undirected graph, returns thedegree(Object)
.If the count is greater than
Integer.MAX_VALUE
, returnsInteger.MAX_VALUE
.- Throws:
IllegalArgumentException
- ifnode
is not an element of this graph
-
equals
For the defaultGraph
implementations, returns true ifthis == object
(reference equality). External implementations are free to define this method as they see fit, as long as they satisfy theObject.equals(Object)
contract.To compare two
Graph
s based on their contents rather than their references, seeGraphs.equivalent(Graph, Graph)
. -
hashCode
int hashCode()For the defaultGraph
implementations, returnsSystem.identityHashCode(this)
. External implementations are free to define this method as they see fit, as long as they satisfy theObject.hashCode()
contract.
-