StarGraphGenerator.java

/* ==========================================
 * JGraphT : a free Java graph-theory library
 * ==========================================
 *
 * Project Info:  http://jgrapht.sourceforge.net/
 * Project Creator:  Barak Naveh (http://sourceforge.net/users/barak_naveh)
 *
 * (C) Copyright 2003-2008, by Barak Naveh and Contributors.
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation,
 * Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
 */
/* -------------------
 * StarGraphGenerator.java
 * -------------------
 * (C) Copyright 2008-2008, by Andrew Newell and Contributors.
 *
 * Original Author:  Andrew Newell
 * Contributor(s):   -
 *
 * $Id: StarGraphGenerator.java 651 2008-12-24 21:13:41Z perfecthash $
 *
 * Changes
 * -------
 * 24-Dec-2008 : Initial revision (AN);
 *
 */
package edu.nd.nina.generate;

import java.util.*;

import edu.nd.nina.*;


/**
 * Generates a <a href="http://mathworld.wolfram.com/StarGraph.html">star
 * graph</a> of any size. This is a graph where every vertex has exactly one
 * edge with a center vertex.
 *
 * @author Andrew Newell
 * @since Dec 21, 2008
 */
public class StarGraphGenerator<V, E>
    implements GraphGenerator<V, E, V>
{
    //~ Static fields/initializers ---------------------------------------------

    public static final String CENTER_VERTEX = "Center Vertex";

    //~ Instance fields --------------------------------------------------------

    private int order;

    //~ Constructors -----------------------------------------------------------

    /**
     * Creates a new StarGraphGenerator object.
     *
     * @param order number of total vertices including the center vertex
     */
    public StarGraphGenerator(int order)
    {
        this.order = order;
    }

    //~ Methods ----------------------------------------------------------------

    /**
     * Generates a star graph with the designated order from the constructor
     */
    public void generateGraph(
        Graph<V, E> target,
        final VertexFactory<V> vertexFactory,
        Map<String, V> resultMap)
    {
        if (order < 1) {
            return;
        }

        //Create center vertex
        V centerVertex = vertexFactory.createVertex();
        target.addVertex(centerVertex);
        if (resultMap != null) {
            resultMap.put(CENTER_VERTEX, centerVertex);
        }

        //Create other vertices
        for (int i = 0; i < (order - 1); i++) {
            V newVertex = vertexFactory.createVertex();
            target.addVertex(newVertex);
        }

        //Add one edge between the center vertex and every other vertex
        Iterator<V> iter = target.vertexSet().iterator();
        while (iter.hasNext()) {
            V v = iter.next();
            if (v != centerVertex) {
                target.addEdge(v, centerVertex);
            }
        }
    }
}

// End StarGraphGenerator.java