edu.uci.ics.jung.graph.util.ParallelEdgeIndexFunction.java Source code

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Here is the source code for edu.uci.ics.jung.graph.util.ParallelEdgeIndexFunction.java

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/*
 * Created on Sep 24, 2005
 *
 * Copyright (c) 2005, The JUNG Authors
 *
 * All rights reserved.
 *
 * This software is open-source under the BSD license; see either
 * "license.txt" or
 * https://github.com/jrtom/jung/blob/master/LICENSE for a description.
 */
package edu.uci.ics.jung.graph.util;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.graph.EndpointPair;
import com.google.common.graph.Network;
import java.util.HashMap;
import java.util.Map;

/**
 * A class which creates and maintains indices for parallel edges. Parallel edges are defined here
 * to be the collection of edges that are returned by <code>graph.edgesConnecting(v, w)</code> for
 * some <code>v</code> and <code>w</code>.
 *
 * <p>At this time, users are responsible for resetting the indices (by calling <code>reset()</code>
 * ) if changes to the graph make it appropriate.
 *
 * @author Joshua O'Madadhain
 * @author Tom Nelson
 */
public class ParallelEdgeIndexFunction<N, E> implements EdgeIndexFunction<E> {
    protected Map<E, Integer> edgeIndex = new HashMap<E, Integer>();
    protected Network<N, E> graph;

    /** @param graph the graph for which this index function is defined */
    public ParallelEdgeIndexFunction(Network<N, E> graph) {
        this.graph = checkNotNull(graph, "graph");
    }

    public int getIndex(E edge) {
        checkNotNull(edge, "edge");
        Integer index = edgeIndex.get(edge);
        if (index == null) {
            EndpointPair<N> endpoints = graph.incidentNodes(edge);
            N u = endpoints.nodeU();
            N v = endpoints.nodeV();
            int count = 0;
            for (E connectingEdge : graph.edgesConnecting(u, v)) {
                edgeIndex.put(connectingEdge, count++);
            }
            return edgeIndex.get(edge);
        }
        return index;
    }

    public void reset(E edge) {
        edgeIndex.remove(checkNotNull(edge, "edge"));
    }

    public void reset() {
        edgeIndex.clear();
    }
}