Source for java.text.CollationKey

   1: /* CollationKey.java -- Precomputed collation value
   2:    Copyright (C) 1998, 1999, 2000, 2003, 2005  Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10:  
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: 
  39: package java.text;
  40: 
  41: import java.util.Arrays;
  42: 
  43: /* Written using "Java Class Libraries", 2nd edition, plus online
  44:  * API docs for JDK 1.2 from http://www.javasoft.com.
  45:  * Status: Believed complete and correct.
  46:  */
  47: 
  48: /**
  49:  * This class represents a pre-computed series of bits representing a
  50:  * <code>String</code> for under a particular <code>Collator</code>.  This
  51:  * value may be compared bitwise against another <code>CollationKey</code>
  52:  * representing a different <code>String</code> under the same
  53:  * <code>Collator</code> in a manner than is usually more efficient than
  54:  * using the raw <code>Collator</code> compare methods.  There is overhead
  55:  * associated with calculating this value, so it is generally not
  56:  * advisable to compute <code>CollationKey</code>'s unless multiple 
  57:  * comparisons against a <code>String</code> will be done.  (For example,
  58:  * in a sort routine).
  59:  * <p>
  60:  * This class cannot be instantiated directly.  Instead, a 
  61:  * <code>CollationKey</code> is created by calling the
  62:  * <code>getCollationKey</code> method on an instance of <code>Collator</code>.
  63:  *
  64:  * @author Aaron M. Renn (arenn@urbanophile.com)
  65:  * @author Tom Tromey (tromey@cygnus.com)
  66:  * @date March 25, 1999
  67:  */
  68: public class CollationKey implements Comparable<CollationKey>
  69: {
  70:   /**
  71:    * This is the <code>Collator</code> this object was created from.
  72:    */
  73:   private Collator collator;
  74: 
  75:   /**
  76:    * This is the <code>String</code> this object represents.
  77:    */
  78:   private String originalText;
  79: 
  80:   /**
  81:    * This is the bit value for this key.
  82:    */
  83:   private byte[] key;
  84: 
  85:   CollationKey (Collator collator, String originalText, byte[] key)
  86:   {
  87:     this.collator = collator;
  88:     this.originalText = originalText;
  89:     this.key = key;
  90:   }
  91: 
  92:   /**
  93:    * This method compares the specified object to this one.  An integer is 
  94:    * returned which indicates whether the specified object is less than, 
  95:    * greater than, or equal to this object.
  96:    *
  97:    * @param ck The <code>CollationKey</code> to compare against this one.
  98:    *
  99:    * @return A negative integer if this object is less than the specified object, 0 if it is equal or a positive integer if it is greater than the specified object.
 100:    */
 101:   public int compareTo (CollationKey ck)
 102:   {
 103:     int max = Math.min (key.length, ck.key.length);
 104: 
 105:     for (int i = 0; i < max; ++i)
 106:       {
 107:     if (key[i] != ck.key[i])
 108:       return key[i] - ck.key[i];
 109:       }
 110: 
 111:     return key.length - ck.key.length;
 112:   }
 113: 
 114:   /**
 115:    * This method tests the specified <code>Object</code> for equality with
 116:    * this object.  This will be true if and only if:
 117:    * <p>
 118:    * <ul>
 119:    * <li>The specified object must not be <code>null</code></li>
 120:    * <li>The specified object is an instance of <code>CollationKey</code>.</li>
 121:    * <li>The specified object was created from the same <code>Collator</code>
 122:    * as this object.</li>
 123:    * <li>The specified object has the same source string and bit key as
 124:    * this object.</li>
 125:    * </ul>
 126:    *
 127:    * @param obj The <code>Object</code> to test for equality.
 128:    *
 129:    * @return <code>true</code> if the specified object is equal to this one, <code>false</code> otherwise.
 130:    */
 131:   public boolean equals (Object obj)
 132:   {
 133:     if (! (obj instanceof CollationKey))
 134:       return false;
 135: 
 136:     CollationKey ck = (CollationKey) obj;
 137: 
 138:     if (ck.collator != collator)
 139:       return false;
 140: 
 141:     if (!ck.getSourceString ().equals (getSourceString ()))
 142:       return false;
 143: 
 144:     if (! Arrays.equals (ck.toByteArray (), toByteArray ()))
 145:       return false;
 146: 
 147:     return true;
 148:   }
 149: 
 150:   /**
 151:    * This method returns the <code>String</code> that this object was created
 152:    * from.
 153:    *
 154:    * @return The source <code>String</code> for this object.
 155:    */
 156:   public String getSourceString()
 157:   {
 158:     return originalText;
 159:   }
 160: 
 161:   /**
 162:    * This method returns a hash value for this object.  The hash value
 163:    * returned will be the hash code of the bit key so that identical bit
 164:    * keys will return the same value.
 165:    *
 166:    * @return A hash value for this object.
 167:    */
 168:   public int hashCode()
 169:   {
 170:     // We just follow BitSet instead of thinking up something new.
 171:     long h = originalText.hashCode();
 172:     for (int i = key.length - 1; i >= 0; --i)
 173:       h ^= key[i] * (i + 1);
 174:     return (int) ((h >> 32) ^ h);
 175:   }
 176:   
 177:   /**
 178:    * This method returns the collation bit sequence as a byte array.
 179:    *
 180:    * @return A byte array containing the collation bit sequence.
 181:    */
 182:   public byte[] toByteArray()
 183:   {
 184:     return key;
 185:   }
 186: }