betweeness java

Betweenness is a centrality measure used in graph theory to identify the importance of a node in a network. It measures the number of shortest paths that go through a node.

In Java, you can calculate the betweenness centrality of a node in a graph using the JUNG (Java Universal Network/Graph Framework) library. Here is an example code snippet:

import edu.uci.ics.jung.algorithms.shortestpath.BFSDistanceLabeler;
import edu.uci.ics.jung.algorithms.shortestpath.DijkstraShortestPath;
import edu.uci.ics.jung.graph.Graph;
import edu.uci.ics.jung.graph.UndirectedSparseGraph;
import edu.uci.ics.jung.graph.util.EdgeType;
import edu.uci.ics.jung.graph.util.Pair;
import java.util.HashMap;
import java.util.Map;

public class BetweennessCentralityExample {

    public static void main(String[] args) {
        // create an undirected graph
        Graph<Integer, String> graph = new UndirectedSparseGraph<>();

        // add vertices
        graph.addVertex(1);
        graph.addVertex(2);
        graph.addVertex(3);
        graph.addVertex(4);

        // add edges
        graph.addEdge("e1", new Pair<>(1, 2), EdgeType.UNDIRECTED);
        graph.addEdge("e2", new Pair<>(1, 3), EdgeType.UNDIRECTED);
        graph.addEdge("e3", new Pair<>(2, 3), EdgeType.UNDIRECTED);
        graph.addEdge("e4", new Pair<>(3, 4), EdgeType.UNDIRECTED);

        // calculate the betweenness centrality
        Map<Integer, Double> betweenness = new HashMap<>();
        for (Integer v : graph.getVertices()) {
            BFSDistanceLabeler<Integer, String> labeler = new BFSDistanceLabeler<>();
            labeler.labelDistances(graph, v);
            for (Integer u : graph.getVertices()) {
                if (!v.equals(u)) {
                    DijkstraShortestPath<Integer, String> shortestPath = new DijkstraShortestPath<>(graph);
                    shortestPath.reset();
                    shortestPath.setSource(u);
                    shortestPath.setGoal(v);
                    shortestPath.compute();
                    double numShortestPaths = shortestPath.getPaths(u).size();
                    if (numShortestPaths > 0) {
                        double numShortestPathsContainingV = 0;
                        for (String path : shortestPath.getPaths(u)) {
                            if (path.contains(Integer.toString(v))) {
                                numShortestPathsContainingV++;
                            }
                        }
                        double betweennessCentrality = numShortestPathsContainingV / numShortestPaths;
                        if (betweenness.containsKey(v)) {
                            betweenness.put(v, betweenness.get(v) + betweennessCentrality);
                        } else {
                            betweenness.put(v, betweennessCentrality);
                        }
                    }
                }
            }
        }

        // print the betweenness centrality of each node
        for (Integer v : betweenness.keySet()) {
            System.out.println("Node " + v + ": " + betweenness.get(v));
        }
    }
}

This code creates an undirected graph with four vertices and four edges. It then calculates the betweenness centrality of each node using a modified version of the Brandes algorithm. Finally, it prints the betweenness centrality of each node to the console.