Interface PredecessorsFunction<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 @DoNotMock("Implement with a lambda, or use GraphBuilder to build a Graph with the desired edges") public interface PredecessorsFunction<N>
A functional interface for graphstructured data.This interface is meant to be used as the type of a parameter to graph algorithms (such as topological sort) that only need a way of accessing the predecessors of a node in a graph.
Usage
Given an algorithm, for example:
you will invoke it depending on the graph representation you're using.public <N> someGraphAlgorithm(N startNode, PredecessorsFunction<N> predecessorsFunction);
If you have an instance of one of the primary
common.graph
types (Graph
,ValueGraph
, andNetwork
):
This works because those types each implementsomeGraphAlgorithm(startNode, graph);
PredecessorsFunction
. 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 methodgetParents()
that retrieves its predecessors in a graph:someGraphAlgorithm(startNode, MyNode::getParents);
If you have some other mechanism for returning the predecessors of a node, or one that doesn't return a
Iterable<? extends N>
, then you can use a lambda to perform a more general transformation:someGraphAlgorithm(startNode, node > ImmutableList.of(node.mother(), node.father()));
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
, orNetwork
.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
All Methods Instance Methods Abstract Methods Modifier and Type Method Description java.lang.Iterable<? extends N>
predecessors(N 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.



Method Detail

predecessors
java.lang.Iterable<? extends N> predecessors(N 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.Some algorithms that operate on a
PredecessorsFunction
may produce undesired results if the returnedIterable
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: Nonnull
 Usable as
Map
keys (see the Guava User Guide's section on graph elements for details)
 Throws:
java.lang.IllegalArgumentException
 ifnode
is not an element of this graph

