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 program and the accompanying materials are dual-licensed under
 * either
 *
 * (a) the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation, or (at your option) any
 * later version.
 *
 * or (per the licensee's choosing)
 *
 * (b) the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation.
 */
/* -------------------
 * StarGraphGenerator.java
 * -------------------
 * (C) Copyright 2008-2008, by Andrew Newell and Contributors.
 *
 * Original Author:  Andrew Newell
 * Contributor(s):   -
 *
 * $Id$
 *
 * Changes
 * -------
 * 24-Dec-2008 : Initial revision (AN);
 *
 */
package org.jgrapht.generate;

import java.util.*;

import org.jgrapht.*;


/**
 * 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>
{
    

    public static final String CENTER_VERTEX = "Center Vertex";

    

    private int order;

    

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

    

    /**
     * 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