Guava: Google Core Libraries for Java 33.1.0-jre · com.google.common.graph.Graph

An interface for graph-structured data, whose edges are anonymous entities with no identity or information of their own.

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

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:

Method Summary

Modifier and Type	Method and Description
public Set<N>	adjacentNodes(N node) Redeclares com.google.common.graph.BaseGraph.adjacentNodes. Returns a live view of the nodes which have an incident edge in common with `node` in this graph.
public boolean	allowsSelfLoops() Redeclares com.google.common.graph.BaseGraph.allowsSelfLoops. Returns true if this graph allows self-loops (edges that connect a node to itself).
public int	degree(N node) Redeclares com.google.common.graph.BaseGraph.degree. Returns the count of `node`'s incident edges, counting self-loops twice (equivalently, the number of times an edge touches `node`).
public Set<EndpointPair<N>>	edges() Redeclares com.google.common.graph.BaseGraph.edges. Returns all edges in this graph.
public boolean	equals(Object object) Returns `true` iff `object` is a `Graph` that has the same elements and the same structural relationships as those in this graph.
public boolean	hasEdgeConnecting(N nodeU, N nodeV) Redeclares com.google.common.graph.BaseGraph.hasEdgeConnecting. Returns true if there is an edge that directly connects `nodeU` to `nodeV`.
public boolean	hasEdgeConnecting(EndpointPair<N> endpoints) Redeclares com.google.common.graph.BaseGraph.hasEdgeConnecting. Returns true if there is an edge that directly connects `endpoints` (in the order, if any, specified by `endpoints`).
public int	hashCode() Returns the hash code for this graph.
public ElementOrder<N>	incidentEdgeOrder() Redeclares com.google.common.graph.BaseGraph.incidentEdgeOrder. Returns an `ElementOrder` that specifies the order of iteration for the elements of `edges()`, `adjacentNodes(Object)`, `predecessors(Object)`, `successors(Object)` and `incidentEdges(Object)`.
public Set<EndpointPair<N>>	incidentEdges(N node) Redeclares com.google.common.graph.BaseGraph.incidentEdges. Returns a live view of the edges in this graph whose endpoints include `node`.
public int	inDegree(N node) Redeclares com.google.common.graph.BaseGraph.inDegree. Returns the count of `node`'s incoming edges (equal to `predecessors(node).size()`) in a directed graph.
public boolean	isDirected() Redeclares com.google.common.graph.BaseGraph.isDirected. Returns true if the edges in this graph are directed.
public ElementOrder<N>	nodeOrder() Redeclares com.google.common.graph.BaseGraph.nodeOrder. Returns the order of iteration for the elements of `nodes()`.
public Set<N>	nodes() Redeclares com.google.common.graph.BaseGraph.nodes. Returns all nodes in this graph, in the order specified by `nodeOrder()`.
public int	outDegree(N node) Redeclares com.google.common.graph.BaseGraph.outDegree. Returns the count of `node`'s outgoing edges (equal to `successors(node).size()`) in a directed graph.
public Set<N>	predecessors(N node) Redeclares com.google.common.graph.BaseGraph.predecessors. 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.
public Set<N>	successors(N node) Redeclares com.google.common.graph.BaseGraph.successors. 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 Detail

adjacentNodes back to summary

adjacentNodes	back to summary
public Set<N> adjacentNodes(N node) Redeclares com.google.common.graph.BaseGraph.adjacentNodes. 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 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 Annotations @Override Exceptions IllegalArgumentException: if `node` is not an element of this graph

public Set<N> adjacentNodes(N node)

Redeclares com.google.common.graph.BaseGraph.adjacentNodes.

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 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

Annotations

@Override

Exceptions

IllegalArgumentException:: if node is not an element of this graph

allowsSelfLoops back to summary

allowsSelfLoops	back to summary
public boolean allowsSelfLoops() Redeclares com.google.common.graph.BaseGraph.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`. Annotations @Override

public boolean allowsSelfLoops()

Redeclares com.google.common.graph.BaseGraph.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.

Annotations

@Override

degree back to summary

degree	back to summary
public int degree(N node) Redeclares com.google.common.graph.BaseGraph.degree. Returns the count of `node`'s incident edges, counting self-loops twice (equivalently, the number of times an edge touches `node`). For directed graphs, this is equal to `inDegree(node) + outDegree(node)`. For undirected graphs, 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`. Annotations @Override Exceptions IllegalArgumentException: if `node` is not an element of this graph

public int degree(N node)

Redeclares com.google.common.graph.BaseGraph.degree.

Returns the count of node's incident edges, counting self-loops twice (equivalently, the number of times an edge touches node).

For directed graphs, this is equal to inDegree(node) + outDegree(node).

For undirected graphs, 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.

Annotations

@Override

Exceptions

IllegalArgumentException:: if node is not an element of this graph

edges	back to summary
public Set<EndpointPair<N>> edges() Redeclares com.google.common.graph.BaseGraph.edges. Returns all edges in this graph. Annotations @Override

edges

back to summary

public Set<EndpointPair<N>> edges()

Redeclares com.google.common.graph.BaseGraph.edges.

Returns all edges in this graph.

Annotations

@Override

equals back to summary

equals	back to summary
public boolean equals(Object object) Returns `true` iff `object` is a `Graph` that has the same elements and the same structural relationships as those in this graph. Thus, two graphs 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`. Graph properties besides `directedness` do not affect equality. For example, two graphs may be considered equal even if one allows self-loops and the other doesn't. Additionally, the order in which nodes or edges are added to the graph, and the order in which they are iterated over, are irrelevant. A reference implementation of this is provided by `AbstractGraph#equals(Object)`. Annotations @Override

public boolean equals(Object object)

Returns true iff object is a Graph that has the same elements and the same structural relationships as those in this graph.

Thus, two graphs 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.

Graph properties besides directedness do not affect equality. For example, two graphs may be considered equal even if one allows self-loops and the other doesn't. Additionally, the order in which nodes or edges are added to the graph, and the order in which they are iterated over, are irrelevant.

A reference implementation of this is provided by AbstractGraph#equals(Object).

Annotations

@Override

hasEdgeConnecting back to summary

hasEdgeConnecting	back to summary
public boolean hasEdgeConnecting(N nodeU, N nodeV) Redeclares com.google.common.graph.BaseGraph.hasEdgeConnecting. Returns true if there is an edge that directly connects `nodeU` to `nodeV`. This is equivalent to `nodes().contains(nodeU) && successors(nodeU).contains(nodeV)`. In an undirected graph, this is equal to `hasEdgeConnecting(nodeV, nodeU)`. Annotations @Override Since 23.0

public boolean hasEdgeConnecting(N nodeU, N nodeV)

Redeclares com.google.common.graph.BaseGraph.hasEdgeConnecting.

Returns true if there is an edge that directly connects nodeU to nodeV. This is equivalent to nodes().contains(nodeU) && successors(nodeU).contains(nodeV).

In an undirected graph, this is equal to hasEdgeConnecting(nodeV, nodeU).

Annotations

@Override

Since

23.0

hasEdgeConnecting back to summary

hasEdgeConnecting	back to summary
public boolean hasEdgeConnecting(EndpointPair<N> endpoints) Redeclares com.google.common.graph.BaseGraph.hasEdgeConnecting. Returns true if there is an edge that directly connects `endpoints` (in the order, if any, specified by `endpoints`). This is equivalent to `edges().contains(endpoints)`. Unlike the other `EndpointPair`-accepting methods, this method does not throw if the endpoints are unordered and the graph is directed; it simply returns `false`. This is for consistency with the behavior of `Collection#contains(Object)` (which does not generally throw if the object cannot be present in the collection), and the desire to have this method's behavior be compatible with `edges().contains(endpoints)`. Annotations @Override Since 27.1

public boolean hasEdgeConnecting(EndpointPair<N> endpoints)

Redeclares com.google.common.graph.BaseGraph.hasEdgeConnecting.

Returns true if there is an edge that directly connects endpoints (in the order, if any, specified by endpoints). This is equivalent to edges().contains(endpoints).

Unlike the other EndpointPair-accepting methods, this method does not throw if the endpoints are unordered and the graph is directed; it simply returns false. This is for consistency with the behavior of Collection#contains(Object) (which does not generally throw if the object cannot be present in the collection), and the desire to have this method's behavior be compatible with edges().contains(endpoints).

Annotations

@Override

Since

27.1

hashCode back to summary

hashCode	back to summary
public int hashCode() Returns the hash code for this graph. The hash code of a graph is defined as the hash code of the set returned by `edges()`. A reference implementation of this is provided by `AbstractGraph#hashCode()`. Annotations @Override

public int hashCode()

Returns the hash code for this graph. The hash code of a graph is defined as the hash code of the set returned by edges().

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

Annotations

@Override

incidentEdgeOrder back to summary

incidentEdgeOrder	back to summary
public ElementOrder<N> incidentEdgeOrder() Redeclares com.google.common.graph.BaseGraph.incidentEdgeOrder. Returns an `ElementOrder` that specifies the order of iteration for the elements of `edges()`, `adjacentNodes(Object)`, `predecessors(Object)`, `successors(Object)` and `incidentEdges(Object)`. Annotations @Override Since 29.0

public ElementOrder<N> incidentEdgeOrder()

Redeclares com.google.common.graph.BaseGraph.incidentEdgeOrder.

Returns an ElementOrder that specifies the order of iteration for the elements of edges(), adjacentNodes(Object), predecessors(Object), successors(Object) and incidentEdges(Object).

Annotations

@Override

Since

29.0

incidentEdges back to summary

incidentEdges	back to summary
public Set<EndpointPair<N>> incidentEdges(N node) Redeclares com.google.common.graph.BaseGraph.incidentEdges. Returns a live view of the edges in this graph whose endpoints include `node`. This is equal to the union of incoming and outgoing edges. 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 Annotations @Override Exceptions IllegalArgumentException: if `node` is not an element of this graph Since 24.0

public Set<EndpointPair<N>> incidentEdges(N node)

Redeclares com.google.common.graph.BaseGraph.incidentEdges.

Returns a live view of the edges in this graph whose endpoints include node.

This is equal to the union of incoming and outgoing edges.

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

Annotations

@Override

Exceptions

IllegalArgumentException:: if node is not an element of this graph

Since

24.0

inDegree back to summary

inDegree	back to summary
public int inDegree(N node) Redeclares com.google.common.graph.BaseGraph.inDegree. Returns the count of `node`'s incoming edges (equal to `predecessors(node).size()`) in a directed graph. In an undirected graph, returns the `degree(Object)`. If the count is greater than `Integer.MAX_VALUE`, returns `Integer.MAX_VALUE`. Annotations @Override Exceptions IllegalArgumentException: if `node` is not an element of this graph

public int inDegree(N node)

Redeclares com.google.common.graph.BaseGraph.inDegree.

Returns the count of node's incoming edges (equal to predecessors(node).size()) in a directed graph. In an undirected graph, returns the degree(Object).

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

Annotations

@Override

Exceptions

IllegalArgumentException:: if node is not an element of this graph

isDirected back to summary

isDirected	back to summary
public boolean isDirected() Redeclares com.google.common.graph.BaseGraph.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. Annotations @Override

public boolean isDirected()

Redeclares com.google.common.graph.BaseGraph.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.

Annotations

@Override

nodeOrder back to summary

nodeOrder	back to summary
public ElementOrder<N> nodeOrder() Redeclares com.google.common.graph.BaseGraph.nodeOrder. Returns the order of iteration for the elements of `nodes()`. Annotations @Override

public ElementOrder<N> nodeOrder()

Redeclares com.google.common.graph.BaseGraph.nodeOrder.

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

Annotations

@Override

nodes back to summary

nodes	back to summary
public Set<N> nodes() Redeclares com.google.common.graph.BaseGraph.nodes. Returns all nodes in this graph, in the order specified by `nodeOrder()`. Annotations @Override

public Set<N> nodes()

Redeclares com.google.common.graph.BaseGraph.nodes.

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

Annotations

@Override

outDegree back to summary

outDegree	back to summary
public int outDegree(N node) Redeclares com.google.common.graph.BaseGraph.outDegree. Returns the count of `node`'s outgoing edges (equal to `successors(node).size()`) in a directed graph. In an undirected graph, returns the `degree(Object)`. If the count is greater than `Integer.MAX_VALUE`, returns `Integer.MAX_VALUE`. Annotations @Override Exceptions IllegalArgumentException: if `node` is not an element of this graph

public int outDegree(N node)

Redeclares com.google.common.graph.BaseGraph.outDegree.

Returns the count of node's outgoing edges (equal to successors(node).size()) in a directed graph. In an undirected graph, returns the degree(Object).

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

Annotations

@Override

Exceptions

IllegalArgumentException:: if node is not an element of this graph

predecessors back to summary

predecessors	back to summary
public Set<N> predecessors(N node) Redeclares com.google.common.graph.BaseGraph.predecessors. 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 Annotations @Override Exceptions IllegalArgumentException: if `node` is not an element of this graph

public Set<N> predecessors(N node)

Redeclares com.google.common.graph.BaseGraph.predecessors.

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).

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

Annotations

@Override

Exceptions

IllegalArgumentException:: if node is not an element of this graph

successors back to summary

successors	back to summary
public Set<N> successors(N node) Redeclares com.google.common.graph.BaseGraph.successors. 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 Annotations @Override Exceptions IllegalArgumentException: if `node` is not an element of this graph

public Set<N> successors(N node)

Redeclares com.google.common.graph.BaseGraph.successors.

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).

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

Annotations

@Override

Exceptions

IllegalArgumentException:: if node is not an element of this graph

public Interface Graph<N>

Capabilities

Building a Graph

Additional documentation

Method Summary

Method Detail

Building a `Graph`