Question

The methods getSource() and getTarget() of DefaultEdge on org.jgrapht.graph.DefaultEdge are protected.

How should I access source and target vertices of each of the edges returned by the edgeSet() of org.jgrapht.graph.SimpleGraph ?

The code below shows what is happening.

import java.util.Set;

import org.jgrapht.UndirectedGraph;
import org.jgrapht.graph.DefaultEdge;
import org.jgrapht.graph.SimpleGraph;

public class TestEdges
{
    public static void main(String [] args)
    {
        UndirectedGraph<String, DefaultEdge> g =
            new SimpleGraph<String, DefaultEdge>(DefaultEdge.class);

        String A = "A";
        String B = "B";
        String C = "C";

        // add the vertices
        g.addVertex(A);
        g.addVertex(B);
        g.addVertex(C);

        g.addEdge(A, B);
        g.addEdge(B, C);
        g.addEdge(A, C);

        Set<DefaultEdge> edges = g.edgeSet();

        for(DefaultEdge edge : edges) {
            String v1   = edge.getSource(); // Error getSource() is protected method
            String v2   = edge.getTarget(); // Error getTarget() is protected method
        }
    }
}

Answer 1

The “correct” method to access edges source and target, according to JGraphT mailing list is to use the method getEdgeSource(E) and getEdgeTarget(E) from the interface Interface Graph<V,E> of org.jgrapht

the modification of the code is then

for(DefaultEdge edge : edges) {
   String v1   = g.getEdgeSource(edge);
   String v2   = g.getEdgeTarget(edge);
}