Source for org.jfree.chart.HashUtilities

   1: /* ===========================================================
   2:  * JFreeChart : a free chart library for the Java(tm) platform
   3:  * ===========================================================
   4:  *
   5:  * (C) Copyright 2000-2007, by Object Refinery Limited and Contributors.
   6:  *
   7:  * Project Info:  http://www.jfree.org/jfreechart/index.html
   8:  *
   9:  * This library is free software; you can redistribute it and/or modify it 
  10:  * under the terms of the GNU Lesser General Public License as published by 
  11:  * the Free Software Foundation; either version 2.1 of the License, or 
  12:  * (at your option) any later version.
  13:  *
  14:  * This library is distributed in the hope that it will be useful, but 
  15:  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
  16:  * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
  17:  * License for more details.
  18:  *
  19:  * You should have received a copy of the GNU Lesser General Public
  20:  * License along with this library; if not, write to the Free Software
  21:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
  22:  * USA.  
  23:  *
  24:  * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
  25:  * in the United States and other countries.]
  26:  *
  27:  * ------------------
  28:  * HashUtilities.java
  29:  * ------------------
  30:  * (C) Copyright 2006, 2007, by Object Refinery Limited;
  31:  *
  32:  * Original Author:  David Gilbert (for Object Refinery Limited);
  33:  * Contributor(s):   -;
  34:  *
  35:  * Changes
  36:  * -------
  37:  * 03-Oct-2006 : Version 1 (DG);
  38:  * 06-Mar-2007 : Fix for hashCodeForDoubleArray() method (DG);
  39:  * 13-Nov-2007 : Added new utility methods (DG);
  40:  *
  41:  */
  42: 
  43: package org.jfree.chart;
  44: 
  45: import java.awt.GradientPaint;
  46: import java.awt.Paint;
  47: import java.awt.Stroke;
  48: 
  49: /**
  50:  * Some utility methods for calculating hash codes.  
  51:  * 
  52:  * @since 1.0.3
  53:  */
  54: public class HashUtilities {
  55:     
  56:     /**
  57:      * Returns a hash code for a <code>Paint</code> instance.  If 
  58:      * <code>p</code> is <code>null</code>, this method returns zero.
  59:      * 
  60:      * @param p  the paint (<code>null</code> permitted).
  61:      * 
  62:      * @return The hash code.
  63:      */
  64:     public static int hashCodeForPaint(Paint p) {
  65:         if (p == null) {
  66:             return 0;
  67:         }
  68:         int result = 0;
  69:         // handle GradientPaint as a special case
  70:         if (p instanceof GradientPaint) {
  71:             GradientPaint gp = (GradientPaint) p;
  72:             result = 193;
  73:             result = 37 * result + gp.getColor1().hashCode();
  74:             result = 37 * result + gp.getPoint1().hashCode();
  75:             result = 37 * result + gp.getColor2().hashCode();
  76:             result = 37 * result + gp.getPoint2().hashCode();
  77:         }
  78:         else {
  79:             // we assume that all other Paint instances implement equals() and
  80:             // hashCode()...of course that might not be true, but what can we
  81:             // do about it?
  82:             result = p.hashCode();
  83:         }
  84:         return result;
  85:     }
  86:     
  87:     /**
  88:      * Returns a hash code for a <code>double[]</code> instance.  If the array
  89:      * is <code>null</code>, this method returns zero.
  90:      * 
  91:      * @param a  the array (<code>null</code> permitted).
  92:      * 
  93:      * @return The hash code.
  94:      */
  95:     public static int hashCodeForDoubleArray(double[] a) {
  96:         if (a == null) { 
  97:             return 0;
  98:         }
  99:         int result = 193;
 100:         long temp;
 101:         for (int i = 0; i < a.length; i++) {
 102:             temp = Double.doubleToLongBits(a[i]);
 103:             result = 29 * result + (int) (temp ^ (temp >>> 32));
 104:         }
 105:         return result;
 106:     }
 107:     
 108:     /**
 109:      * Returns a hash value based on a seed value and the value of a boolean
 110:      * primitive.
 111:      * 
 112:      * @param pre  the seed value.
 113:      * @param b  the boolean value.
 114:      * 
 115:      * @return A hash value.
 116:      * 
 117:      * @since 1.0.7
 118:      */
 119:     public static int hashCode(int pre, boolean b) {
 120:         return 37 * pre + (b ? 0 : 1);
 121:     }
 122:     
 123:     /**
 124:      * Returns a hash value based on a seed value and the value of a double
 125:      * primitive.
 126:      * 
 127:      * @param pre  the seed value.
 128:      * @param d  the double value.
 129:      * 
 130:      * @return A hash value.
 131:      * 
 132:      * @since 1.0.7
 133:      */
 134:     public static int hashCode(int pre, double d) {
 135:         long l = Double.doubleToLongBits(d);
 136:         return 37 * pre + (int) (l ^ (l >>> 32));
 137:     }
 138:     
 139:     /**
 140:      * Returns a hash value based on a seed value and a paint instance.
 141:      * 
 142:      * @param pre  the seed value.
 143:      * @param p  the paint (<code>null</code> permitted).
 144:      * 
 145:      * @return A hash value.
 146:      * 
 147:      * @since 1.0.7
 148:      */
 149:     public static int hashCode(int pre, Paint p) {
 150:         return 37 * pre + hashCodeForPaint(p);
 151:     }
 152: 
 153:     /**
 154:      * Returns a hash value based on a seed value and a stroke instance.
 155:      * 
 156:      * @param pre  the seed value.
 157:      * @param s  the stroke (<code>null</code> permitted).
 158:      * 
 159:      * @return A hash value.
 160:      * 
 161:      * @since 1.0.7
 162:      */
 163:     public static int hashCode(int pre, Stroke s) {
 164:         int h = (s != null ? s.hashCode() : 0);
 165:         return 37 * pre + h;
 166:     }
 167: 
 168:     /**
 169:      * Returns a hash value based on a seed value and a string instance.
 170:      * 
 171:      * @param pre  the seed value.
 172:      * @param s  the string (<code>null</code> permitted).
 173:      * 
 174:      * @return A hash value.
 175:      * 
 176:      * @since 1.0.7
 177:      */
 178:     public static int hashCode(int pre, String s) {
 179:         int h = (s != null ? s.hashCode() : 0);
 180:         return 37 * pre + h;
 181:     }
 182: 
 183:     /**
 184:      * Returns a hash value based on a seed value and a <code>Comparable</code>
 185:      * instance.
 186:      * 
 187:      * @param pre  the seed value.
 188:      * @param c  the comparable (<code>null</code> permitted).
 189:      * 
 190:      * @return A hash value.
 191:      * 
 192:      * @since 1.0.7
 193:      */
 194:     public static int hashCode(int pre, Comparable c) {
 195:         int h = (c != null ? c.hashCode() : 0);
 196:         return 37 * pre + h;
 197:     }
 198: }