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jfreechart example source code file (HashUtilities.java)

This example jfreechart source code file (HashUtilities.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - jfreechart tags/keywords

awt, booleanlist, comparable, comparable, gradientpaint, gradientpaint, hashutilities, object, object, paint, paintlist, string, stroke, stroke, strokelist

The jfreechart HashUtilities.java source code

/* ===========================================================
 * JFreeChart : a free chart library for the Java(tm) platform
 * ===========================================================
 *
 * (C) Copyright 2000-2007, by Object Refinery Limited and Contributors.
 *
 * Project Info:  http://www.jfree.org/jfreechart/index.html
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
 * USA.  
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
 * in the United States and other countries.]
 *
 * ------------------
 * HashUtilities.java
 * ------------------
 * (C) Copyright 2006, 2007, by Object Refinery Limited;
 *
 * Original Author:  David Gilbert (for Object Refinery Limited);
 * Contributor(s):   -;
 *
 * Changes
 * -------
 * 03-Oct-2006 : Version 1 (DG);
 * 06-Mar-2007 : Fix for hashCodeForDoubleArray() method (DG);
 * 13-Nov-2007 : Added new utility methods (DG);
 * 22-Nov-2007 : Added hashCode() method for 'int' (DG);
 * 05-Dec-2007 : Added special methods to handle BooleanList, PaintList,
 *               and StrokeList (DG);
 *
 */

package org.jfree.chart;

import java.awt.GradientPaint;
import java.awt.Paint;
import java.awt.Stroke;

import org.jfree.util.BooleanList;
import org.jfree.util.PaintList;
import org.jfree.util.StrokeList;

/**
 * Some utility methods for calculating hash codes.  
 * 
 * @since 1.0.3
 */
public class HashUtilities {
    
    /**
     * Returns a hash code for a <code>Paint instance.  If 
     * <code>p is null, this method returns zero.
     * 
     * @param p  the paint (<code>null permitted).
     * 
     * @return The hash code.
     */
    public static int hashCodeForPaint(Paint p) {
        if (p == null) {
            return 0;
        }
        int result = 0;
        // handle GradientPaint as a special case
        if (p instanceof GradientPaint) {
            GradientPaint gp = (GradientPaint) p;
            result = 193;
            result = 37 * result + gp.getColor1().hashCode();
            result = 37 * result + gp.getPoint1().hashCode();
            result = 37 * result + gp.getColor2().hashCode();
            result = 37 * result + gp.getPoint2().hashCode();
        }
        else {
            // we assume that all other Paint instances implement equals() and
            // hashCode()...of course that might not be true, but what can we
            // do about it?
            result = p.hashCode();
        }
        return result;
    }
    
    /**
     * Returns a hash code for a <code>double[] instance.  If the array
     * is <code>null, this method returns zero.
     * 
     * @param a  the array (<code>null permitted).
     * 
     * @return The hash code.
     */
    public static int hashCodeForDoubleArray(double[] a) {
        if (a == null) { 
            return 0;
        }
        int result = 193;
        long temp;
        for (int i = 0; i < a.length; i++) {
            temp = Double.doubleToLongBits(a[i]);
            result = 29 * result + (int) (temp ^ (temp >>> 32));
        }
        return result;
    }
    
    /**
     * Returns a hash value based on a seed value and the value of a boolean
     * primitive.
     * 
     * @param pre  the seed value.
     * @param b  the boolean value.
     * 
     * @return A hash value.
     * 
     * @since 1.0.7
     */
    public static int hashCode(int pre, boolean b) {
        return 37 * pre + (b ? 0 : 1);
    }
    
    /**
     * Returns a hash value based on a seed value and the value of an int
     * primitive.
     * 
     * @param pre  the seed value.
     * @param i  the int value.
     * 
     * @return A hash value.
     * 
     * @since 1.0.8
     */
    public static int hashCode(int pre, int i) {
        return 37 * pre + i;
    }

    /**
     * Returns a hash value based on a seed value and the value of a double
     * primitive.
     * 
     * @param pre  the seed value.
     * @param d  the double value.
     * 
     * @return A hash value.
     * 
     * @since 1.0.7
     */
    public static int hashCode(int pre, double d) {
        long l = Double.doubleToLongBits(d);
        return 37 * pre + (int) (l ^ (l >>> 32));
    }
    
    /**
     * Returns a hash value based on a seed value and a paint instance.
     * 
     * @param pre  the seed value.
     * @param p  the paint (<code>null permitted).
     * 
     * @return A hash value.
     * 
     * @since 1.0.7
     */
    public static int hashCode(int pre, Paint p) {
        return 37 * pre + hashCodeForPaint(p);
    }

    /**
     * Returns a hash value based on a seed value and a stroke instance.
     * 
     * @param pre  the seed value.
     * @param s  the stroke (<code>null permitted).
     * 
     * @return A hash value.
     * 
     * @since 1.0.7
     */
    public static int hashCode(int pre, Stroke s) {
        int h = (s != null ? s.hashCode() : 0);
        return 37 * pre + h;
    }

    /**
     * Returns a hash value based on a seed value and a string instance.
     * 
     * @param pre  the seed value.
     * @param s  the string (<code>null permitted).
     * 
     * @return A hash value.
     * 
     * @since 1.0.7
     */
    public static int hashCode(int pre, String s) {
        int h = (s != null ? s.hashCode() : 0);
        return 37 * pre + h;
    }

    /**
     * Returns a hash value based on a seed value and a <code>Comparable
     * instance.
     * 
     * @param pre  the seed value.
     * @param c  the comparable (<code>null permitted).
     * 
     * @return A hash value.
     * 
     * @since 1.0.7
     */
    public static int hashCode(int pre, Comparable c) {
        int h = (c != null ? c.hashCode() : 0);
        return 37 * pre + h;
    }

    /**
     * Returns a hash value based on a seed value and an <code>Object
     * instance.
     * 
     * @param pre  the seed value.
     * @param obj  the object (<code>null permitted).
     * 
     * @return A hash value.
     * 
     * @since 1.0.8
     */
    public static int hashCode(int pre, Object obj) {
        int h = (obj != null ? obj.hashCode() : 0);
        return 37 * pre + h;
    }
    
    /**
     * Computes a hash code for a {@link BooleanList}.  In the latest version
     * of JCommon, the {@link BooleanList} class should implement the hashCode()
     * method correctly, but we compute it here anyway so that we can work with 
     * older versions of JCommon (back to 1.0.0).
     * 
     * @param pre  the seed value.
     * @param list  the list (<code>null permitted).
     * 
     * @return The hash code.
     * 
     * @since 1.0.9
     */
    public static int hashCode(int pre, BooleanList list) {
        if (list == null) {
            return pre;
        }
        int result = 127;
        int size = list.size();
        result = HashUtilities.hashCode(result, size);
        
        // for efficiency, we just use the first, last and middle items to
        // compute a hashCode...
        if (size > 0) {
            result = HashUtilities.hashCode(result, list.getBoolean(0));
            if (size > 1) {
                result = HashUtilities.hashCode(result, 
                        list.getBoolean(size - 1));
                if (size > 2) {
                    result = HashUtilities.hashCode(result, 
                            list.getBoolean(size / 2));
                }
            }
        }
        return 37 * pre + result;
    }

    /**
     * Computes a hash code for a {@link PaintList}.  In the latest version
     * of JCommon, the {@link PaintList} class should implement the hashCode()
     * method correctly, but we compute it here anyway so that we can work with 
     * older versions of JCommon (back to 1.0.0).
     * 
     * @param pre  the seed value.
     * @param list  the list (<code>null permitted).
     * 
     * @return The hash code.
     * 
     * @since 1.0.9
     */
    public static int hashCode(int pre, PaintList list) {
        if (list == null) {
            return pre;
        }
        int result = 127;
        int size = list.size();
        result = HashUtilities.hashCode(result, size);
        
        // for efficiency, we just use the first, last and middle items to
        // compute a hashCode...
        if (size > 0) {
            result = HashUtilities.hashCode(result, list.getPaint(0));
            if (size > 1) {
                result = HashUtilities.hashCode(result, 
                        list.getPaint(size - 1));
                if (size > 2) {
                    result = HashUtilities.hashCode(result, 
                            list.getPaint(size / 2));
                }
            }
        }
        return 37 * pre + result;
    }

    /**
     * Computes a hash code for a {@link StrokeList}.  In the latest version
     * of JCommon, the {@link StrokeList} class should implement the hashCode()
     * method correctly, but we compute it here anyway so that we can work with 
     * older versions of JCommon (back to 1.0.0).
     * 
     * @param pre  the seed value.
     * @param list  the list (<code>null permitted).
     * 
     * @return The hash code.
     * 
     * @since 1.0.9
     */
    public static int hashCode(int pre, StrokeList list) {
        if (list == null) {
            return pre;
        }
        int result = 127;
        int size = list.size();
        result = HashUtilities.hashCode(result, size);
        
        // for efficiency, we just use the first, last and middle items to
        // compute a hashCode...
        if (size > 0) {
            result = HashUtilities.hashCode(result, list.getStroke(0));
            if (size > 1) {
                result = HashUtilities.hashCode(result, 
                        list.getStroke(size - 1));
                if (size > 2) {
                    result = HashUtilities.hashCode(result, 
                            list.getStroke(size / 2));
                }
            }
        }
        return 37 * pre + result;
    }
}

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