com.google.common.graph

Interface SuccessorsFunction<N>

Type Parameters:

N - Node parameter type

All Known Subinterfaces:

com.google.common.graph.BaseGraph<N>, Graph<N>, MutableGraph<N>, MutableNetwork<N,E>, MutableValueGraph<N,V>, Network<N,E>, ValueGraph<N,V>

All Known Implementing Classes:

AbstractGraph, AbstractNetwork, AbstractValueGraph, ImmutableGraph, ImmutableNetwork, ImmutableValueGraph

@Beta
public interface SuccessorsFunction<N>

A functional interface for graph-structured data.

This interface is meant to be used as the type of a parameter to graph algorithms (such as breadth first traversal) that only need a way of accessing the successors of a node in a graph.

Usage

Given an algorithm, for example:

 public <N> someGraphAlgorithm(N startNode, SuccessorsFunction<N> successorsFunction);
 

you will invoke it depending on the graph representation you're using.

If you have an instance of one of the primary common.graph types (Graph, ValueGraph, and Network):

 someGraphAlgorithm(startNode, graph);
 

This works because those types each implement SuccessorsFunction. It will also work with any other implementation of this interface.

If you have your own graph implementation based around a custom node type MyNode, which has a method getChildren() that retrieves its successors in a graph:

 someGraphAlgorithm(startNode, MyNode::getChildren);
 

If you have some other mechanism for returning the successors of a node, or one that doesn't return an Iterable<? extends N>, then you can use a lambda to perform a more general transformation:

 someGraphAlgorithm(startNode, node -> ImmutableList.of(node.leftChild(), node.rightChild()));
 

Graph algorithms that need additional capabilities (accessing both predecessors and successors, iterating over the edges, etc.) should declare their input to be of a type that provides those capabilities, such as Graph, ValueGraph, or Network.

Additional documentation

See the Guava User Guide for the common.graph package ("Graphs Explained") for additional documentation, including notes for implementors

Since:

23.0

Author:

Joshua O'Madadhain, Jens Nyman

Method Summary

Modifier and Type	Method and Description
Iterable<? extends N>	successors(N node) Returns 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

successors

Iterable<? extends N> successors(N node)

Returns 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.

This is not the same as "all nodes reachable from node by following outgoing edges". For that functionality, see Graphs.reachableNodes(Graph, Object).

Some algorithms that operate on a SuccessorsFunction may produce undesired results if the returned Iterable contains duplicate elements. Implementations of such algorithms should document their behavior in the presence of duplicates.

The elements of the returned Iterable must each be:

• Non-null
• Usable as Map keys (see the Guava User Guide's section on graph elements for details)

Throws:

IllegalArgumentException - if node is not an element of this graph