Source for java.text.Collator

   1: /* Collator.java -- Perform locale dependent String comparisons.
   2:    Copyright (C) 1998, 1999, 2000, 2001, 2004, 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.Comparator;
  42: import java.util.Locale;
  43: import java.util.MissingResourceException;
  44: import java.util.ResourceBundle;
  45: 
  46: /**
  47:  * This class is the abstract superclass of classes which perform 
  48:  * locale dependent <code>String</code> comparisons.  A caller requests
  49:  * an instance of <code>Collator</code> for a particular locale using
  50:  * the <code>getInstance()</code> static method in this class.  That method
  51:  * will return a locale specific subclass of <code>Collator</code> which
  52:  * can be used to perform <code>String</code> comparisons for that locale.
  53:  * If a subclass of <code>Collator</code> cannot be located for a particular
  54:  * locale, a default instance for the current locale will be returned.  
  55:  *
  56:  * In addition to setting the correct locale, there are two additional
  57:  * settings that can be adjusted to affect <code>String</code> comparisons:
  58:  * strength and decomposition.  The strength value determines the level
  59:  * of signficance of character differences required for them to sort
  60:  * differently.  (For example, whether or not capital letters are considered
  61:  * different from lower case letters).  The decomposition value affects how
  62:  * variants of the same character are treated for sorting purposes.  (For
  63:  * example, whether or not an accent is signficant or not).  These settings
  64:  * are described in detail in the documentation for the methods and values
  65:  * that are related to them.
  66:  *
  67:  * @author Tom Tromey (tromey@cygnus.com)
  68:  * @author Aaron M. Renn (arenn@urbanophile.com)
  69:  * @date March 18, 1999
  70:  */
  71: /* Written using "Java Class Libraries", 2nd edition, plus online
  72:  * API docs for JDK 1.2 from http://www.javasoft.com.
  73:  * Status: Mostly complete, but parts stubbed out.  Look for FIXME.
  74:  */
  75: public abstract class Collator implements Comparator, Cloneable
  76: {
  77:   /**
  78:    * This constant is a strength value which indicates that only primary
  79:    * differences between characters will be considered signficant.  As an
  80:    * example, two completely different English letters such as 'a' and 'b'
  81:    * are considered to have a primary difference.
  82:    */
  83:   public static final int PRIMARY = 0;
  84:   
  85:   /**
  86:    * This constant is a strength value which indicates that only secondary
  87:    * or primary differences between characters will be considered
  88:    * significant.  An example of a secondary difference between characters
  89:    * are instances of the same letter with different accented forms.
  90:    */
  91:   public static final int SECONDARY = 1;
  92:   
  93:   /**
  94:    * This constant is a strength value which indicates that tertiary,
  95:    * secondary, and primary differences will be considered during sorting.
  96:    * An example of a tertiary difference is capitalization of a given letter.
  97:    * This is the default value for the strength setting.
  98:    */
  99:   public static final int TERTIARY = 2;
 100:   
 101:   /**
 102:    * This constant is a strength value which indicates that any difference
 103:    * at all between character values are considered significant.
 104:    */
 105:   public static final int IDENTICAL = 3;
 106:   
 107:   /**
 108:    * This constant indicates that accented characters won't be decomposed
 109:    * when performing comparisons.  This will yield the fastest results, but
 110:    * will only work correctly in call cases for languages which do not
 111:    * use accents such as English.
 112:    */
 113:   public static final int NO_DECOMPOSITION = 0;
 114:   
 115:   /**
 116:    * This constant indicates that only characters which are canonical variants
 117:    * in Unicode 2.0 will be decomposed prior to performing comparisons.  This
 118:    * will cause accented languages to be sorted correctly.  This is the
 119:    * default decomposition value.
 120:    */
 121:   public static final int CANONICAL_DECOMPOSITION = 1;
 122:   
 123:   /**
 124:    * This constant indicates that both canonical variants and compatibility
 125:    * variants in Unicode 2.0 will be decomposed prior to performing
 126:    * comparisons.  This is the slowest mode, but is required to get the
 127:    * correct sorting for certain languages with certain special formats.
 128:    */
 129:   public static final int FULL_DECOMPOSITION = 2;
 130: 
 131:   /**
 132:    * This method initializes a new instance of <code>Collator</code> to have
 133:    * the default strength (TERTIARY) and decomposition 
 134:    * (CANONICAL_DECOMPOSITION) settings.  This constructor is protected and
 135:    * is for use by subclasses only.  Non-subclass callers should use the
 136:    * static <code>getInstance()</code> methods of this class to instantiate
 137:    * <code>Collation</code> objects for the desired locale.
 138:    */
 139:   protected Collator ()
 140:   {
 141:     strength = TERTIARY;
 142:     decmp = CANONICAL_DECOMPOSITION;
 143:   }
 144: 
 145:   /**
 146:    * This method compares the two <code>String</code>'s and returns an
 147:    * integer indicating whether or not the first argument is less than,
 148:    * equal to, or greater than the second argument.  The comparison is
 149:    * performed according to the rules of the locale for this 
 150:    * <code>Collator</code> and the strength and decomposition rules in
 151:    * effect.
 152:    *
 153:    * @param source The first object to compare
 154:    * @param target The second object to compare
 155:    *
 156:    * @return A negative integer if str1 &lt; str2, 0 if str1 == str2, or
 157:    * a positive integer if str1 &gt; str2. 
 158:    */
 159:   public abstract int compare (String source, String target);
 160: 
 161:   /**
 162:    * This method compares the two <code>Object</code>'s and returns an
 163:    * integer indicating whether or not the first argument is less than,
 164:    * equal to, or greater than the second argument.  These two objects
 165:    * must be <code>String</code>'s or an exception will be thrown.
 166:    *
 167:    * @param o1 The first object to compare
 168:    * @param o2 The second object to compare
 169:    *
 170:    * @return A negative integer if obj1 &lt; obj2, 0 if obj1 == obj2, or
 171:    * a positive integer if obj1 &gt; obj2. 
 172:    *
 173:    * @exception ClassCastException If the arguments are not instances
 174:    * of <code>String</code>. 
 175:    */
 176:   public int compare (Object o1, Object o2)
 177:   {
 178:     return compare ((String) o1, (String) o2);
 179:   }
 180: 
 181:   /**
 182:    * This method tests the specified object for equality against this
 183:    * object.  This will be true if and only if the following conditions are
 184:    * met:
 185:    * <ul>
 186:    * <li>The specified object is not <code>null</code>.</li>
 187:    * <li>The specified object is an instance of <code>Collator</code>.</li>
 188:    * <li>The specified object has the same strength and decomposition
 189:    * settings as this object.</li>
 190:    * </ul>
 191:    *
 192:    * @param obj The <code>Object</code> to test for equality against
 193:    *            this object. 
 194:    *
 195:    * @return <code>true</code> if the specified object is equal to
 196:    * this one, <code>false</code> otherwise.
 197:    */
 198:   public boolean equals (Object obj)
 199:   {
 200:     if (! (obj instanceof Collator))
 201:       return false;
 202:     Collator c = (Collator) obj;
 203:     return decmp == c.decmp && strength == c.strength;
 204:   }
 205: 
 206:   /**
 207:    * This method tests whether the specified <code>String</code>'s are equal
 208:    * according to the collation rules for the locale of this object and
 209:    * the current strength and decomposition settings.
 210:    *
 211:    * @param source The first <code>String</code> to compare
 212:    * @param target The second <code>String</code> to compare
 213:    *
 214:    * @return <code>true</code> if the two strings are equal,
 215:    * <code>false</code> otherwise. 
 216:    */
 217:   public boolean equals (String source, String target)
 218:   {
 219:     return compare (source, target) == 0;
 220:   }
 221: 
 222:   /**
 223:    * This method returns a copy of this <code>Collator</code> object.
 224:    *
 225:    * @return A duplicate of this object.
 226:    */
 227:   public Object clone ()
 228:   {
 229:     try
 230:       {
 231:     return super.clone ();
 232:       }
 233:     catch (CloneNotSupportedException _)
 234:       {
 235:     return null;
 236:       }
 237:   }
 238: 
 239:   /**
 240:    * This method returns an array of <code>Locale</code> objects which is
 241:    * the list of locales for which <code>Collator</code> objects exist.
 242:    *
 243:    * @return The list of locales for which <code>Collator</code>'s exist.
 244:    */
 245:   public static synchronized Locale[] getAvailableLocales ()
 246:   {
 247:     // FIXME
 248:     Locale[] l = new Locale[1];
 249:     l[0] = Locale.US;
 250:     return l;
 251:   }
 252: 
 253:   /**
 254:    * This method transforms the specified <code>String</code> into a
 255:    * <code>CollationKey</code> for faster comparisons.  This is useful when
 256:    * comparisons against a string might be performed multiple times, such
 257:    * as during a sort operation.
 258:    *
 259:    * @param source The <code>String</code> to convert.
 260:    *
 261:    * @return A <code>CollationKey</code> for the specified <code>String</code>.
 262:    */
 263:   public abstract CollationKey getCollationKey (String source);
 264: 
 265:   /**
 266:    * This method returns the current decomposition setting for this
 267:    * object.  This * will be one of NO_DECOMPOSITION,
 268:    * CANONICAL_DECOMPOSITION, or * FULL_DECOMPOSITION.  See the
 269:    * documentation for those constants for an * explanation of this
 270:    * setting.
 271:    *
 272:    * @return The current decomposition setting.
 273:    */
 274:   public synchronized int getDecomposition ()
 275:   {
 276:     return decmp;
 277:   }
 278: 
 279:   /**
 280:    * This method returns an instance of <code>Collator</code> for the
 281:    * default locale.
 282:    *
 283:    * @return A <code>Collator</code> for the default locale.
 284:    */
 285:   public static Collator getInstance ()
 286:   {
 287:     return getInstance (Locale.getDefault());
 288:   }
 289: 
 290:   /**
 291:    * This method returns an instance of <code>Collator</code> for the
 292:    * specified locale.  If no <code>Collator</code> exists for the desired
 293:    * locale, a <code>Collator</code> for the default locale will be returned.
 294:    *
 295:    * @param loc The desired localed to load a <code>Collator</code> for.
 296:    *
 297:    * @return A <code>Collator</code> for the requested locale
 298:    */
 299:   public static Collator getInstance (Locale loc)
 300:   {
 301:     ResourceBundle res;
 302:     String pattern;
 303:     try
 304:       {
 305:     res = ResourceBundle.getBundle("gnu.java.locale.LocaleInformation",
 306:                        loc, ClassLoader.getSystemClassLoader());
 307:     pattern = res.getString("collation_rules");
 308:       }
 309:     catch (MissingResourceException x)
 310:       {
 311:     pattern = "<0<1<2<3<4<5<6<7<8<9<A,a<b,B<c,C<d,D<e,E<f,F<g,G<h,H<i,I<j,J<k,K" +
 312:         "<l,L<m,M<n,N<o,O<p,P<q,Q<r,R<s,S<t,T<u,U<v,V<w,W<x,X<y,Y<z,Z";
 313:       }
 314:     try
 315:       {
 316:     return new RuleBasedCollator (pattern);
 317:       }
 318:     catch (ParseException x)
 319:       {
 320:     throw (InternalError)new InternalError().initCause(x);
 321:       }
 322:   }
 323: 
 324:   /**
 325:    * This method returns the current strength setting for this object.  This
 326:    * will be one of PRIMARY, SECONDARY, TERTIARY, or IDENTICAL.  See the
 327:    * documentation for those constants for an explanation of this setting.
 328:    *
 329:    * @return The current strength setting.
 330:    */
 331:   public synchronized int getStrength ()
 332:   {
 333:     return strength;
 334:   }
 335: 
 336:   /**
 337:    * This method returns a hash code value for this object.
 338:    *
 339:    * @return A hash value for this object.
 340:    */
 341:   public abstract int hashCode ();
 342: 
 343:   /**
 344:    * This method sets the decomposition setting for this object to the
 345:    * specified value.  This must be one of NO_DECOMPOSITION,
 346:    * CANONICAL_DECOMPOSITION, or FULL_DECOMPOSITION.  Otherwise an
 347:    * exception will be thrown.  See the documentation for those
 348:    * contants for an explanation of this setting.
 349:    *
 350:    * @param mode The new decomposition setting.
 351:    *
 352:    * @exception IllegalArgumentException If the requested
 353:    * decomposition setting is not valid.
 354:    */
 355:   public synchronized void setDecomposition (int mode)
 356:   {
 357:     if (mode != NO_DECOMPOSITION
 358:     && mode != CANONICAL_DECOMPOSITION
 359:     && mode != FULL_DECOMPOSITION)
 360:       throw new IllegalArgumentException ();
 361:     decmp = mode;
 362:   }
 363: 
 364:   /**
 365:    * This method sets the strength setting for this object to the specified
 366:    * value.  This must be one of PRIMARY, SECONDARY, TERTIARY, or IDENTICAL.
 367:    * Otherwise an exception is thrown. See the documentation for these
 368:    * constants for an explanation of this setting.
 369:    * 
 370:    * @param strength The new strength setting.
 371:    *
 372:    * @exception IllegalArgumentException If the requested strength
 373:    * setting value is not valid.
 374:    */
 375:   public synchronized void setStrength (int strength)
 376:   {
 377:     if (strength != PRIMARY && strength != SECONDARY
 378:     && strength != TERTIARY && strength != IDENTICAL)
 379:       throw new IllegalArgumentException ();
 380:     this.strength = strength;
 381:   }
 382: 
 383:   // Decompose a single character and append results to the buffer.
 384:   // FIXME: for libgcj this is a native method which handles
 385:   // decomposition.  For Classpath, for now, it does nothing.
 386:   final void decomposeCharacter (char c, StringBuffer buf)
 387:   {
 388:     buf.append (c);
 389:   }
 390: 
 391:   /**
 392:    * This is the current collation decomposition setting.
 393:    */
 394:   int decmp;
 395: 
 396:   /**
 397:    * This is the current collation strength setting.
 398:    */
 399:   int strength;
 400: }