gomp-20050608-branch/libjava/classpath/java/text/CollationKey.java

   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 final class CollationKey implements Comparable
  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 compares the specified object to this one.  The specified
 116    * object must be an instance of <code>CollationKey</code> or an exception
 117    * will be thrown.  An integer is returned which indicates whether the
 118    * specified object is less than, greater than, or equal to this object.
 119    *
 120    * @param obj The <code>Object</code> to compare against this one.
 121    *
 122    * @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.
 123    */
 124   public int compareTo (Object obj)
 125   {
 126     return compareTo ((CollationKey) obj);
 127   }
 128
 129   /**
 130    * This method tests the specified <code>Object</code> for equality with
 131    * this object.  This will be true if and only if:
 132    * <p>
 133    * <ul>
 134    * <li>The specified object must not be <code>null</code></li>
 135    * <li>The specified object is an instance of <code>CollationKey</code>.</li>
 136    * <li>The specified object was created from the same <code>Collator</code>
 137    * as this object.</li>
 138    * <li>The specified object has the same source string and bit key as
 139    * this object.</li>
 140    * </ul>
 141    *
 142    * @param obj The <code>Object</code> to test for equality.
 143    *
 144    * @return <code>true</code> if the specified object is equal to this one, <code>false</code> otherwise.
 145    */
 146   public boolean equals (Object obj)
 147   {
 148     if (! (obj instanceof CollationKey))
 149       return false;
 150
 151     CollationKey ck = (CollationKey) obj;
 152
 153     if (ck.collator != collator)
 154       return false;
 155
 156     if (!ck.getSourceString ().equals (getSourceString ()))
 157       return false;
 158
 159     if (! Arrays.equals (ck.toByteArray (), toByteArray ()))
 160       return false;
 161
 162     return true;
 163   }
 164
 165   /**
 166    * This method returns the <code>String</code> that this object was created
 167    * from.
 168    *
 169    * @return The source <code>String</code> for this object.
 170    */
 171   public String getSourceString()
 172   {
 173     return originalText;
 174   }
 175
 176   /**
 177    * This method returns a hash value for this object.  The hash value
 178    * returned will be the hash code of the bit key so that identical bit
 179    * keys will return the same value.
 180    *
 181    * @return A hash value for this object.
 182    */
 183   public int hashCode()
 184   {
 185     // We just follow BitSet instead of thinking up something new.
 186     long h = originalText.hashCode();
 187     for (int i = key.length - 1; i >= 0; --i)
 188       h ^= key[i] * (i + 1);
 189     return (int) ((h >> 32) ^ h);
 190   }
 191
 192   /**
 193    * This method returns the collation bit sequence as a byte array.
 194    *
 195    * @return A byte array containing the collation bit sequence.
 196    */
 197   public byte[] toByteArray()
 198   {
 199     return key;
 200   }
 201 }