com.google.common.graph

Class Graphs

java.lang.Object

com.google.common.graph.Graphs

@Beta
public final class Graphs
extends Object

Static utility methods for Graph and Network instances.

Since:

20.0

Author:

James Sexton, Joshua O'Madadhain

Method Summary

Modifier and Type	Method and Description
static <N> MutableGraph<N>	copyOf(Graph<N> graph) Creates a mutable copy of graph with the same nodes and edges.
static <N,E> MutableNetwork<N,E>	copyOf(Network<N,E> network) Creates a mutable copy of network with the same nodes and edges.
static <N,V> MutableValueGraph<N,V>	copyOf(ValueGraph<N,V> graph) Creates a mutable copy of graph with the same nodes, edges, and edge values.
static boolean	equivalent(Graph<?> graphA, Graph<?> graphB) Returns true iff graphA and graphB have the same elements and the same relationships between elements, as exposed via the Graph interface.
static boolean	equivalent(Network<?,?> networkA, Network<?,?> networkB) Returns true iff networkA and networkB have the same elements and the same relationships between elements, as exposed via the Network interface.
static boolean	equivalent(ValueGraph<?,?> graphA, ValueGraph<?,?> graphB) Returns true iff graphA and graphB have the same elements (including edge values) and the same relationships between elements, as exposed via the ValueGraph interface.
static boolean	hasCycle(Graph<?> graph) Returns true iff graph has at least one cycle.
static boolean	hasCycle(Network<?,?> network) Returns true iff network has at least one cycle.
static <N> MutableGraph<N>	inducedSubgraph(Graph<N> graph, Iterable<? extends N> nodes) Returns an induced subgraph of graph.
static <N,E> MutableNetwork<N,E>	inducedSubgraph(Network<N,E> network, Iterable<? extends N> nodes) Returns an induced subgraph of network.
static <N,V> MutableValueGraph<N,V>	inducedSubgraph(ValueGraph<N,V> graph, Iterable<? extends N> nodes) Returns an induced subgraph of graph.
static <N> Set<N>	reachableNodes(Graph<N> graph, Object node) Returns the set of nodes that are reachable from node.
static <N> Graph<N>	transitiveClosure(Graph<N> graph) Returns the transitive closure of graph.
static <N> Graph<N>	transpose(Graph<N> graph) Returns a view of graph with the direction (if any) of every edge reversed.
static <N,E> Network<N,E>	transpose(Network<N,E> network) Returns a view of network with the direction (if any) of every edge reversed.
static <N,V> ValueGraph<N,V>	transpose(ValueGraph<N,V> graph) Returns a view of graph with the direction (if any) of every edge reversed.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

hasCycle

public static boolean hasCycle(Graph<?> graph)

Returns true iff graph has at least one cycle. A cycle is defined as a non-empty subset of edges in a graph arranged to form a path (a sequence of adjacent outgoing edges) starting and ending with the same node.

This method will detect any non-empty cycle, including self-loops (a cycle of length 1).

hasCycle

public static boolean hasCycle(Network<?,?> network)

Returns true iff network has at least one cycle. A cycle is defined as a non-empty subset of edges in a graph arranged to form a path (a sequence of adjacent outgoing edges) starting and ending with the same node.

This method will detect any non-empty cycle, including self-loops (a cycle of length 1).

transitiveClosure

public static <N> Graph<N> transitiveClosure(Graph<N> graph)

Returns the transitive closure of graph. The transitive closure of a graph is another graph with an edge connecting node A to node B iff node B is reachable from node A.

This is a "snapshot" based on the current topology of graph, rather than a live view of the transitive closure of graph. In other words, the returned Graph will not be updated after modifications to graph.

reachableNodes

public static <N> Set<N> reachableNodes(Graph<N> graph,
                                        Object node)

Returns the set of nodes that are reachable from node. Node B is defined as reachable from node A if there exists a path (a sequence of adjacent outgoing edges) starting at node A and ending at node B. Note that a node is always reachable from itself via a zero-length path.

This is a "snapshot" based on the current topology of graph, rather than a live view of the set of nodes reachable from node. In other words, the returned Set will not be updated after modifications to graph.

Throws:

IllegalArgumentException - if node is not present in graph

equivalent

public static boolean equivalent(@Nullable
                                 Graph<?> graphA,
                                 @Nullable
                                 Graph<?> graphB)

Returns true iff graphA and graphB have the same elements and the same relationships between elements, as exposed via the Graph interface.

Thus, two graphs A and B are equivalent if both are null or 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 equivalence. For example, two graphs may be considered equivalent 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.

equivalent

public static boolean equivalent(@Nullable
                                 ValueGraph<?,?> graphA,
                                 @Nullable
                                 ValueGraph<?,?> graphB)

Returns true iff graphA and graphB have the same elements (including edge values) and the same relationships between elements, as exposed via the ValueGraph interface.

Thus, two value graphs A and B are equivalent if both are null or 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.
• Each edge in A has a value equal to the value of the corresponding edge in B.

Graph properties besides directedness do not affect equivalence. For example, two graphs may be considered equivalent 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.

equivalent

public static boolean equivalent(@Nullable
                                 Network<?,?> networkA,
                                 @Nullable
                                 Network<?,?> networkB)

Returns true iff networkA and networkB have the same elements and the same relationships between elements, as exposed via the Network interface.

Thus, two networks A and B are equivalent if both are null or 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.
• Each edge in A connects the same nodes in the same direction (if any) as the corresponding edge in B.

Network properties besides directedness do not affect equivalence. 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.

transpose

public static <N> Graph<N> transpose(Graph<N> graph)

Returns a view of graph with the direction (if any) of every edge reversed. All other properties remain intact, and further updates to graph will be reflected in the view.

transpose

public static <N,V> ValueGraph<N,V> transpose(ValueGraph<N,V> graph)

Returns a view of graph with the direction (if any) of every edge reversed. All other properties remain intact, and further updates to graph will be reflected in the view.

transpose

public static <N,E> Network<N,E> transpose(Network<N,E> network)

Returns a view of network with the direction (if any) of every edge reversed. All other properties remain intact, and further updates to network will be reflected in the view.

inducedSubgraph

public static <N> MutableGraph<N> inducedSubgraph(Graph<N> graph,
                                                  Iterable<? extends N> nodes)

Returns an induced subgraph of graph. This subgraph is a new graph that contains all of the nodes in nodes, and all of the edges from graph for which both nodes are contained by nodes.

Throws:

IllegalArgumentException - if any element in nodes is not a node in the graph

inducedSubgraph

public static <N,V> MutableValueGraph<N,V> inducedSubgraph(ValueGraph<N,V> graph,
                                                           Iterable<? extends N> nodes)

Returns an induced subgraph of graph. This subgraph is a new graph that contains all of the nodes in nodes, and all of the edges (and associated edge values) from graph for which both nodes are contained by nodes.

Throws:

IllegalArgumentException - if any element in nodes is not a node in the graph

inducedSubgraph

public static <N,E> MutableNetwork<N,E> inducedSubgraph(Network<N,E> network,
                                                        Iterable<? extends N> nodes)

Returns an induced subgraph of network. This subgraph is a new graph that contains all of the nodes in nodes, and all of the edges from network for which the incident nodes are both contained by nodes.

Throws:

IllegalArgumentException - if any element in nodes is not a node in the graph

copyOf

public static <N> MutableGraph<N> copyOf(Graph<N> graph)

Creates a mutable copy of graph with the same nodes and edges.

copyOf

public static <N,V> MutableValueGraph<N,V> copyOf(ValueGraph<N,V> graph)

Creates a mutable copy of graph with the same nodes, edges, and edge values.

copyOf

public static <N,E> MutableNetwork<N,E> copyOf(Network<N,E> network)

Creates a mutable copy of network with the same nodes and edges.