001    /* ===========================================================
002     * JFreeChart : a free chart library for the Java(tm) platform
003     * ===========================================================
004     *
005     * (C) Copyright 2000-2007, by Object Refinery Limited and Contributors.
006     *
007     * Project Info:  http://www.jfree.org/jfreechart/index.html
008     *
009     * This library is free software; you can redistribute it and/or modify it 
010     * under the terms of the GNU Lesser General Public License as published by 
011     * the Free Software Foundation; either version 2.1 of the License, or 
012     * (at your option) any later version.
013     *
014     * This library is distributed in the hope that it will be useful, but 
015     * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
016     * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
017     * License for more details.
018     *
019     * You should have received a copy of the GNU Lesser General Public
020     * License along with this library; if not, write to the Free Software
021     * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
022     * USA.  
023     *
024     * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
025     * in the United States and other countries.]
026     *
027     * ------------------
028     * HashUtilities.java
029     * ------------------
030     * (C) Copyright 2006, 2007, by Object Refinery Limited;
031     *
032     * Original Author:  David Gilbert (for Object Refinery Limited);
033     * Contributor(s):   -;
034     *
035     * $Id: HashUtilities.java,v 1.1.2.2 2007/03/06 16:00:44 mungady Exp $
036     *
037     * Changes
038     * -------
039     * 03-Oct-2006 : Version 1 (DG);
040     * 06-Mar-2007 : Fix for hashCodeForDoubleArray() method (DG);
041     *
042     */
043    
044    package org.jfree.chart;
045    
046    import java.awt.GradientPaint;
047    import java.awt.Paint;
048    
049    /**
050     * Some utility methods for calculating hash codes.  
051     * 
052     * @since 1.0.3
053     */
054    public class HashUtilities {
055        
056        /**
057         * Returns a hash code for a <code>Paint</code> instance.  If 
058         * <code>p</code> is <code>null</code>, this method returns zero.
059         * 
060         * @param p  the paint (<code>null</code> permitted).
061         * 
062         * @return The hash code.
063         */
064        public static int hashCodeForPaint(Paint p) {
065            if (p == null) 
066                return 0;
067            int result = 0;
068            // handle GradientPaint as a special case
069            if (p instanceof GradientPaint) {
070                GradientPaint gp = (GradientPaint) p;
071                result = 193;
072                result = 37 * result + gp.getColor1().hashCode();
073                result = 37 * result + gp.getPoint1().hashCode();
074                result = 37 * result + gp.getColor2().hashCode();
075                result = 37 * result + gp.getPoint2().hashCode();
076            }
077            else {
078                // we assume that all other Paint instances implement equals() and
079                // hashCode()...of course that might not be true, but what can we
080                // do about it?
081                result = p.hashCode();
082            }
083            return result;
084        }
085        
086        /**
087         * Returns a hash code for a <code>double[]</code> instance.  If the array
088         * is <code>null</code>, this method returns zero.
089         * 
090         * @param a  the array (<code>null</code> permitted).
091         * 
092         * @return The hash code.
093         */
094        public static int hashCodeForDoubleArray(double[] a) {
095            if (a == null) { 
096                return 0;
097            }
098            int result = 193;
099            long temp;
100            for (int i = 0; i < a.length; i++) {
101                temp = Double.doubleToLongBits(a[i]);
102                result = 29 * result + (int) (temp ^ (temp >>> 32));
103            }
104            return result;
105        }
106    
107    }