Source for java.text.Collator

   1: /* Collator.java -- Perform locale dependent String comparisons.
   2:    Copyright (C) 1998, 1999, 2000, 2001, 2004, 2005, 2007  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.text.spi.CollatorProvider;
  42: 
  43: import java.util.Comparator;
  44: import java.util.Locale;
  45: import java.util.MissingResourceException;
  46: import java.util.ResourceBundle;
  47: import java.util.ServiceLoader;
  48: 
  49: /**
  50:  * This class is the abstract superclass of classes which perform 
  51:  * locale dependent <code>String</code> comparisons.  A caller requests
  52:  * an instance of <code>Collator</code> for a particular locale using
  53:  * the <code>getInstance()</code> static method in this class.  That method
  54:  * will return a locale specific subclass of <code>Collator</code> which
  55:  * can be used to perform <code>String</code> comparisons for that locale.
  56:  * If a subclass of <code>Collator</code> cannot be located for a particular
  57:  * locale, a default instance for the current locale will be returned.  
  58:  *
  59:  * In addition to setting the correct locale, there are two additional
  60:  * settings that can be adjusted to affect <code>String</code> comparisons:
  61:  * strength and decomposition.  The strength value determines the level
  62:  * of signficance of character differences required for them to sort
  63:  * differently.  (For example, whether or not capital letters are considered
  64:  * different from lower case letters).  The decomposition value affects how
  65:  * variants of the same character are treated for sorting purposes.  (For
  66:  * example, whether or not an accent is signficant or not).  These settings
  67:  * are described in detail in the documentation for the methods and values
  68:  * that are related to them.
  69:  *
  70:  * @author Tom Tromey (tromey@cygnus.com)
  71:  * @author Aaron M. Renn (arenn@urbanophile.com)
  72:  * @date March 18, 1999
  73:  */
  74: public abstract class Collator implements Comparator<Object>, Cloneable
  75: {
  76:   /**
  77:    * This constant is a strength value which indicates that only primary
  78:    * differences between characters will be considered signficant.  As an
  79:    * example, two completely different English letters such as 'a' and 'b'
  80:    * are considered to have a primary difference.
  81:    */
  82:   public static final int PRIMARY = 0;
  83:   
  84:   /**
  85:    * This constant is a strength value which indicates that only secondary
  86:    * or primary differences between characters will be considered
  87:    * significant.  An example of a secondary difference between characters
  88:    * are instances of the same letter with different accented forms.
  89:    */
  90:   public static final int SECONDARY = 1;
  91:   
  92:   /**
  93:    * This constant is a strength value which indicates that tertiary,
  94:    * secondary, and primary differences will be considered during sorting.
  95:    * An example of a tertiary difference is capitalization of a given letter.
  96:    * This is the default value for the strength setting.
  97:    */
  98:   public static final int TERTIARY = 2;
  99:   
 100:   /**
 101:    * This constant is a strength value which indicates that any difference
 102:    * at all between character values are considered significant.
 103:    */
 104:   public static final int IDENTICAL = 3;
 105:   
 106:   /**
 107:    * This constant indicates that accented characters won't be decomposed
 108:    * when performing comparisons.  This will yield the fastest results, but
 109:    * will only work correctly in call cases for languages which do not
 110:    * use accents such as English.
 111:    */
 112:   public static final int NO_DECOMPOSITION = 0;
 113:   
 114:   /**
 115:    * This constant indicates that only characters which are canonical variants
 116:    * in Unicode 2.0 will be decomposed prior to performing comparisons.  This
 117:    * will cause accented languages to be sorted correctly.  This is the
 118:    * default decomposition value.
 119:    */
 120:   public static final int CANONICAL_DECOMPOSITION = 1;
 121:   
 122:   /**
 123:    * This constant indicates that both canonical variants and compatibility
 124:    * variants in Unicode 2.0 will be decomposed prior to performing
 125:    * comparisons.  This is the slowest mode, but is required to get the
 126:    * correct sorting for certain languages with certain special formats.
 127:    */
 128:   public static final int FULL_DECOMPOSITION = 2;
 129: 
 130:   /**
 131:    * This method initializes a new instance of <code>Collator</code> to have
 132:    * the default strength (TERTIARY) and decomposition 
 133:    * (CANONICAL_DECOMPOSITION) settings.  This constructor is protected and
 134:    * is for use by subclasses only.  Non-subclass callers should use the
 135:    * static <code>getInstance()</code> methods of this class to instantiate
 136:    * <code>Collation</code> objects for the desired locale.
 137:    */
 138:   protected Collator ()
 139:   {
 140:     strength = TERTIARY;
 141:     decmp = CANONICAL_DECOMPOSITION;
 142:   }
 143: 
 144:   /**
 145:    * This method compares the two <code>String</code>'s and returns an
 146:    * integer indicating whether or not the first argument is less than,
 147:    * equal to, or greater than the second argument.  The comparison is
 148:    * performed according to the rules of the locale for this 
 149:    * <code>Collator</code> and the strength and decomposition rules in
 150:    * effect.
 151:    *
 152:    * @param source The first object to compare
 153:    * @param target The second object to compare
 154:    *
 155:    * @return A negative integer if str1 &lt; str2, 0 if str1 == str2, or
 156:    * a positive integer if str1 &gt; str2. 
 157:    */
 158:   public abstract int compare (String source, String target);
 159: 
 160:   /**
 161:    * This method compares the two <code>Object</code>'s and returns an
 162:    * integer indicating whether or not the first argument is less than,
 163:    * equal to, or greater than the second argument.  These two objects
 164:    * must be <code>String</code>'s or an exception will be thrown.
 165:    *
 166:    * @param o1 The first object to compare
 167:    * @param o2 The second object to compare
 168:    *
 169:    * @return A negative integer if obj1 &lt; obj2, 0 if obj1 == obj2, or
 170:    * a positive integer if obj1 &gt; obj2. 
 171:    *
 172:    * @exception ClassCastException If the arguments are not instances
 173:    * of <code>String</code>. 
 174:    */
 175:   public int compare (Object o1, Object o2)
 176:   {
 177:     return compare ((String) o1, (String) o2);
 178:   }
 179: 
 180:   /**
 181:    * This method tests the specified object for equality against this
 182:    * object.  This will be true if and only if the following conditions are
 183:    * met:
 184:    * <ul>
 185:    * <li>The specified object is not <code>null</code>.</li>
 186:    * <li>The specified object is an instance of <code>Collator</code>.</li>
 187:    * <li>The specified object has the same strength and decomposition
 188:    * settings as this object.</li>
 189:    * </ul>
 190:    *
 191:    * @param obj The <code>Object</code> to test for equality against
 192:    *            this object. 
 193:    *
 194:    * @return <code>true</code> if the specified object is equal to
 195:    * this one, <code>false</code> otherwise.
 196:    */
 197:   public boolean equals (Object obj)
 198:   {
 199:     if (! (obj instanceof Collator))
 200:       return false;
 201:     Collator c = (Collator) obj;
 202:     return decmp == c.decmp && strength == c.strength;
 203:   }
 204: 
 205:   /**
 206:    * This method tests whether the specified <code>String</code>'s are equal
 207:    * according to the collation rules for the locale of this object and
 208:    * the current strength and decomposition settings.
 209:    *
 210:    * @param source The first <code>String</code> to compare
 211:    * @param target The second <code>String</code> to compare
 212:    *
 213:    * @return <code>true</code> if the two strings are equal,
 214:    * <code>false</code> otherwise. 
 215:    */
 216:   public boolean equals (String source, String target)
 217:   {
 218:     return compare (source, target) == 0;
 219:   }
 220: 
 221:   /**
 222:    * This method returns a copy of this <code>Collator</code> object.
 223:    *
 224:    * @return A duplicate of this object.
 225:    */
 226:   public Object clone ()
 227:   {
 228:     try
 229:       {
 230:     return super.clone ();
 231:       }
 232:     catch (CloneNotSupportedException _)
 233:       {
 234:     return null;
 235:       }
 236:   }
 237: 
 238:   /**
 239:    * This method returns an array of <code>Locale</code> objects which is
 240:    * the list of locales for which <code>Collator</code> objects exist.
 241:    *
 242:    * @return The list of locales for which <code>Collator</code>'s exist.
 243:    */
 244:   public static synchronized Locale[] getAvailableLocales ()
 245:   {
 246:     // FIXME
 247:     Locale[] l = new Locale[1];
 248:     l[0] = Locale.US;
 249:     return l;
 250:   }
 251: 
 252:   /**
 253:    * This method transforms the specified <code>String</code> into a
 254:    * <code>CollationKey</code> for faster comparisons.  This is useful when
 255:    * comparisons against a string might be performed multiple times, such
 256:    * as during a sort operation.
 257:    *
 258:    * @param source The <code>String</code> to convert.
 259:    *
 260:    * @return A <code>CollationKey</code> for the specified <code>String</code>.
 261:    */
 262:   public abstract CollationKey getCollationKey (String source);
 263: 
 264:   /**
 265:    * This method returns the current decomposition setting for this
 266:    * object.  This * will be one of NO_DECOMPOSITION,
 267:    * CANONICAL_DECOMPOSITION, or * FULL_DECOMPOSITION.  See the
 268:    * documentation for those constants for an * explanation of this
 269:    * setting.
 270:    *
 271:    * @return The current decomposition setting.
 272:    */
 273:   public synchronized int getDecomposition ()
 274:   {
 275:     return decmp;
 276:   }
 277: 
 278:   /**
 279:    * This method returns an instance of <code>Collator</code> for the
 280:    * default locale.
 281:    *
 282:    * @return A <code>Collator</code> for the default locale.
 283:    */
 284:   public static Collator getInstance ()
 285:   {
 286:     return getInstance (Locale.getDefault());
 287:   }
 288: 
 289:   /**
 290:    * This method returns an instance of <code>Collator</code> for the
 291:    * specified locale.  If no <code>Collator</code> exists for the desired
 292:    * locale, the fallback procedure described in
 293:    * {@link java.util.spi.LocaleServiceProvider} is invoked.
 294:    *
 295:    * @param loc The desired locale 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:     String pattern;
 302:     try
 303:       {
 304:     ResourceBundle res =
 305:       ResourceBundle.getBundle("gnu.java.locale.LocaleInformation",
 306:                    loc, ClassLoader.getSystemClassLoader());
 307:     return new RuleBasedCollator(res.getString("collation_rules"));
 308:       }
 309:     catch (MissingResourceException x)
 310:       {
 311:     /* This means runtime support for the locale
 312:      * is not available, so we check providers. */
 313:       }
 314:     catch (ParseException x)
 315:       {
 316:     throw (InternalError)new InternalError().initCause(x);
 317:       }
 318:     for (CollatorProvider p : ServiceLoader.load(CollatorProvider.class))
 319:       {
 320:     for (Locale l : p.getAvailableLocales())
 321:       {
 322:         if (l.equals(loc))
 323:           {
 324:         Collator c = p.getInstance(loc);
 325:         if (c != null)
 326:           return c;
 327:         break;
 328:           }
 329:       }
 330:       }
 331:     if (loc.equals(Locale.ROOT))
 332:       {
 333:     try
 334:       {
 335:         return new RuleBasedCollator("<0<1<2<3<4<5<6<7<8<9<A,a<b,B<c," +
 336:                      "C<d,D<e,E<f,F<g,G<h,H<i,I<j,J<k,K" +
 337:                      "<l,L<m,M<n,N<o,O<p,P<q,Q<r,R<s,S<t,"+
 338:                      "T<u,U<v,V<w,W<x,X<y,Y<z,Z");
 339:       }
 340:     catch (ParseException x)
 341:       {
 342:         throw (InternalError)new InternalError().initCause(x);
 343:       }
 344:       }
 345:     // FIXME
 346:     return getInstance(Locale.US);
 347:   }
 348: 
 349:   /**
 350:    * This method returns the current strength setting for this object.  This
 351:    * will be one of PRIMARY, SECONDARY, TERTIARY, or IDENTICAL.  See the
 352:    * documentation for those constants for an explanation of this setting.
 353:    *
 354:    * @return The current strength setting.
 355:    */
 356:   public synchronized int getStrength ()
 357:   {
 358:     return strength;
 359:   }
 360: 
 361:   /**
 362:    * This method returns a hash code value for this object.
 363:    *
 364:    * @return A hash value for this object.
 365:    */
 366:   public abstract int hashCode ();
 367: 
 368:   /**
 369:    * This method sets the decomposition setting for this object to the
 370:    * specified value.  This must be one of NO_DECOMPOSITION,
 371:    * CANONICAL_DECOMPOSITION, or FULL_DECOMPOSITION.  Otherwise an
 372:    * exception will be thrown.  See the documentation for those
 373:    * contants for an explanation of this setting.
 374:    *
 375:    * @param mode The new decomposition setting.
 376:    *
 377:    * @exception IllegalArgumentException If the requested
 378:    * decomposition setting is not valid.
 379:    */
 380:   public synchronized void setDecomposition (int mode)
 381:   {
 382:     if (mode != NO_DECOMPOSITION
 383:     && mode != CANONICAL_DECOMPOSITION
 384:     && mode != FULL_DECOMPOSITION)
 385:       throw new IllegalArgumentException ();
 386:     decmp = mode;
 387:   }
 388: 
 389:   /**
 390:    * This method sets the strength setting for this object to the specified
 391:    * value.  This must be one of PRIMARY, SECONDARY, TERTIARY, or IDENTICAL.
 392:    * Otherwise an exception is thrown. See the documentation for these
 393:    * constants for an explanation of this setting.
 394:    * 
 395:    * @param strength The new strength setting.
 396:    *
 397:    * @exception IllegalArgumentException If the requested strength
 398:    * setting value is not valid.
 399:    */
 400:   public synchronized void setStrength (int strength)
 401:   {
 402:     if (strength != PRIMARY && strength != SECONDARY
 403:     && strength != TERTIARY && strength != IDENTICAL)
 404:       throw new IllegalArgumentException ();
 405:     this.strength = strength;
 406:   }
 407: 
 408:   // Decompose a single character and append results to the buffer.
 409:   native final void decomposeCharacter (char c, StringBuffer buf);
 410: 
 411:   /**
 412:    * This is the current collation decomposition setting.
 413:    */
 414:   int decmp;
 415: 
 416:   /**
 417:    * This is the current collation strength setting.
 418:    */
 419:   int strength;
 420: }