edu.uci.ics.jung.graph.UndirectedOrderedSparseMultigraph.java Source code

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

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/*
 * Created on Oct 18, 2005
 *
 * Copyright (c) 2005, the JUNG Project and the Regents of the University 
 * of California
 * All rights reserved.
 *
 * This software is open-source under the BSD license; see either
 * "license.txt" or
 * http://jung.sourceforge.net/license.txt for a description.
 */
package edu.uci.ics.jung.graph;

import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.Set;

import org.apache.commons.collections15.Factory;

import edu.uci.ics.jung.graph.util.Pair;

/**
 * An implementation of <code>UndirectedGraph</code> that is suitable for sparse graphs,
 * orders its vertex and edge collections according to insertion time, and permits
 * parallel edges.
 */
@SuppressWarnings("serial")
public class UndirectedOrderedSparseMultigraph<V, E> extends UndirectedSparseMultigraph<V, E>
        implements UndirectedGraph<V, E> {

    /**
     * Returns a {@code Factory} that creates an instance of this graph type.
     * @param <V> the vertex type for the graph factory
     * @param <E> the edge type for the graph factory
     */
    public static <V, E> Factory<UndirectedGraph<V, E>> getFactory() {
        return new Factory<UndirectedGraph<V, E>>() {
            public UndirectedGraph<V, E> create() {
                return new UndirectedOrderedSparseMultigraph<V, E>();
            }
        };
    }

    /**
     * Creates a new instance.
     */
    public UndirectedOrderedSparseMultigraph() {
        vertices = new LinkedHashMap<V, Set<E>>();
        edges = new LinkedHashMap<E, Pair<V>>();
    }

    @Override
    public boolean addVertex(V vertex) {
        if (vertex == null) {
            throw new IllegalArgumentException("vertex may not be null");
        }
        if (!containsVertex(vertex)) {
            vertices.put(vertex, new LinkedHashSet<E>());
            return true;
        } else {
            return false;
        }
    }

    @Override
    public Collection<V> getNeighbors(V vertex) {
        if (!containsVertex(vertex))
            return null;

        Set<V> neighbors = new LinkedHashSet<V>();
        for (E edge : getIncident_internal(vertex)) {
            Pair<V> endpoints = this.getEndpoints(edge);
            V e_a = endpoints.getFirst();
            V e_b = endpoints.getSecond();
            if (vertex.equals(e_a))
                neighbors.add(e_b);
            else
                neighbors.add(e_a);
        }

        return Collections.unmodifiableCollection(neighbors);
    }
}