001    /* Collator.java -- Perform locale dependent String comparisons.
002       Copyright (C) 1998, 1999, 2000, 2001, 2004, 2005, 2007,
003       2008  Free Software Foundation, Inc.
004    
005    This file is part of GNU Classpath.
006    
007    GNU Classpath is free software; you can redistribute it and/or modify
008    it under the terms of the GNU General Public License as published by
009    the Free Software Foundation; either version 2, or (at your option)
010    any later version.
011     
012    GNU Classpath is distributed in the hope that it will be useful, but
013    WITHOUT ANY WARRANTY; without even the implied warranty of
014    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
015    General Public License for more details.
016    
017    You should have received a copy of the GNU General Public License
018    along with GNU Classpath; see the file COPYING.  If not, write to the
019    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
020    02110-1301 USA.
021    
022    Linking this library statically or dynamically with other modules is
023    making a combined work based on this library.  Thus, the terms and
024    conditions of the GNU General Public License cover the whole
025    combination.
026    
027    As a special exception, the copyright holders of this library give you
028    permission to link this library with independent modules to produce an
029    executable, regardless of the license terms of these independent
030    modules, and to copy and distribute the resulting executable under
031    terms of your choice, provided that you also meet, for each linked
032    independent module, the terms and conditions of the license of that
033    module.  An independent module is a module which is not derived from
034    or based on this library.  If you modify this library, you may extend
035    this exception to your version of the library, but you are not
036    obligated to do so.  If you do not wish to do so, delete this
037    exception statement from your version. */
038    
039    
040    package java.text;
041    
042    import gnu.java.locale.LocaleHelper;
043    
044    import java.text.spi.CollatorProvider;
045    
046    import java.util.Comparator;
047    import java.util.Locale;
048    import java.util.MissingResourceException;
049    import java.util.ResourceBundle;
050    import java.util.ServiceLoader;
051    
052    /**
053     * This class is the abstract superclass of classes which perform 
054     * locale dependent <code>String</code> comparisons.  A caller requests
055     * an instance of <code>Collator</code> for a particular locale using
056     * the <code>getInstance()</code> static method in this class.  That method
057     * will return a locale specific subclass of <code>Collator</code> which
058     * can be used to perform <code>String</code> comparisons for that locale.
059     * If a subclass of <code>Collator</code> cannot be located for a particular
060     * locale, a default instance for the current locale will be returned.  
061     *
062     * In addition to setting the correct locale, there are two additional
063     * settings that can be adjusted to affect <code>String</code> comparisons:
064     * strength and decomposition.  The strength value determines the level
065     * of signficance of character differences required for them to sort
066     * differently.  (For example, whether or not capital letters are considered
067     * different from lower case letters).  The decomposition value affects how
068     * variants of the same character are treated for sorting purposes.  (For
069     * example, whether or not an accent is signficant or not).  These settings
070     * are described in detail in the documentation for the methods and values
071     * that are related to them.
072     *
073     * @author Tom Tromey (tromey@cygnus.com)
074     * @author Aaron M. Renn (arenn@urbanophile.com)
075     * @date March 18, 1999
076     */
077    public abstract class Collator implements Comparator<Object>, Cloneable
078    {
079      /**
080       * This constant is a strength value which indicates that only primary
081       * differences between characters will be considered signficant.  As an
082       * example, two completely different English letters such as 'a' and 'b'
083       * are considered to have a primary difference.
084       */
085      public static final int PRIMARY = 0;
086      
087      /**
088       * This constant is a strength value which indicates that only secondary
089       * or primary differences between characters will be considered
090       * significant.  An example of a secondary difference between characters
091       * are instances of the same letter with different accented forms.
092       */
093      public static final int SECONDARY = 1;
094      
095      /**
096       * This constant is a strength value which indicates that tertiary,
097       * secondary, and primary differences will be considered during sorting.
098       * An example of a tertiary difference is capitalization of a given letter.
099       * This is the default value for the strength setting.
100       */
101      public static final int TERTIARY = 2;
102      
103      /**
104       * This constant is a strength value which indicates that any difference
105       * at all between character values are considered significant.
106       */
107      public static final int IDENTICAL = 3;
108      
109      /**
110       * This constant indicates that accented characters won't be decomposed
111       * when performing comparisons.  This will yield the fastest results, but
112       * will only work correctly in call cases for languages which do not
113       * use accents such as English.
114       */
115      public static final int NO_DECOMPOSITION = 0;
116      
117      /**
118       * This constant indicates that only characters which are canonical variants
119       * in Unicode 2.0 will be decomposed prior to performing comparisons.  This
120       * will cause accented languages to be sorted correctly.  This is the
121       * default decomposition value.
122       */
123      public static final int CANONICAL_DECOMPOSITION = 1;
124      
125      /**
126       * This constant indicates that both canonical variants and compatibility
127       * variants in Unicode 2.0 will be decomposed prior to performing
128       * comparisons.  This is the slowest mode, but is required to get the
129       * correct sorting for certain languages with certain special formats.
130       */
131      public static final int FULL_DECOMPOSITION = 2;
132    
133      /**
134       * This method initializes a new instance of <code>Collator</code> to have
135       * the default strength (TERTIARY) and decomposition 
136       * (CANONICAL_DECOMPOSITION) settings.  This constructor is protected and
137       * is for use by subclasses only.  Non-subclass callers should use the
138       * static <code>getInstance()</code> methods of this class to instantiate
139       * <code>Collation</code> objects for the desired locale.
140       */
141      protected Collator ()
142      {
143        strength = TERTIARY;
144        decmp = CANONICAL_DECOMPOSITION;
145      }
146    
147      /**
148       * This method compares the two <code>String</code>'s and returns an
149       * integer indicating whether or not the first argument is less than,
150       * equal to, or greater than the second argument.  The comparison is
151       * performed according to the rules of the locale for this 
152       * <code>Collator</code> and the strength and decomposition rules in
153       * effect.
154       *
155       * @param source The first object to compare
156       * @param target The second object to compare
157       *
158       * @return A negative integer if str1 &lt; str2, 0 if str1 == str2, or
159       * a positive integer if str1 &gt; str2. 
160       */
161      public abstract int compare (String source, String target);
162    
163      /**
164       * This method compares the two <code>Object</code>'s and returns an
165       * integer indicating whether or not the first argument is less than,
166       * equal to, or greater than the second argument.  These two objects
167       * must be <code>String</code>'s or an exception will be thrown.
168       *
169       * @param o1 The first object to compare
170       * @param o2 The second object to compare
171       *
172       * @return A negative integer if obj1 &lt; obj2, 0 if obj1 == obj2, or
173       * a positive integer if obj1 &gt; obj2. 
174       *
175       * @exception ClassCastException If the arguments are not instances
176       * of <code>String</code>. 
177       */
178      public int compare (Object o1, Object o2)
179      {
180        return compare ((String) o1, (String) o2);
181      }
182    
183      /**
184       * This method tests the specified object for equality against this
185       * object.  This will be true if and only if the following conditions are
186       * met:
187       * <ul>
188       * <li>The specified object is not <code>null</code>.</li>
189       * <li>The specified object is an instance of <code>Collator</code>.</li>
190       * <li>The specified object has the same strength and decomposition
191       * settings as this object.</li>
192       * </ul>
193       *
194       * @param obj The <code>Object</code> to test for equality against
195       *            this object. 
196       *
197       * @return <code>true</code> if the specified object is equal to
198       * this one, <code>false</code> otherwise.
199       */
200      public boolean equals (Object obj)
201      {
202        if (! (obj instanceof Collator))
203          return false;
204        Collator c = (Collator) obj;
205        return decmp == c.decmp && strength == c.strength;
206      }
207    
208      /**
209       * This method tests whether the specified <code>String</code>'s are equal
210       * according to the collation rules for the locale of this object and
211       * the current strength and decomposition settings.
212       *
213       * @param source The first <code>String</code> to compare
214       * @param target The second <code>String</code> to compare
215       *
216       * @return <code>true</code> if the two strings are equal,
217       * <code>false</code> otherwise. 
218       */
219      public boolean equals (String source, String target)
220      {
221        return compare (source, target) == 0;
222      }
223    
224      /**
225       * This method returns a copy of this <code>Collator</code> object.
226       *
227       * @return A duplicate of this object.
228       */
229      public Object clone ()
230      {
231        try
232          {
233            return super.clone ();
234          }
235        catch (CloneNotSupportedException _)
236          {
237            return null;
238          }
239      }
240    
241      /**
242       * This method returns an array of <code>Locale</code> objects which is
243       * the list of locales for which <code>Collator</code> objects exist.
244       *
245       * @return The list of locales for which <code>Collator</code>'s exist.
246       */
247      public static synchronized Locale[] getAvailableLocales ()
248      {
249        return LocaleHelper.getCollatorLocales();
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        return getInstance(LocaleHelper.getFallbackLocale(loc));
346      }
347    
348      /**
349       * This method returns the current strength setting for this object.  This
350       * will be one of PRIMARY, SECONDARY, TERTIARY, or IDENTICAL.  See the
351       * documentation for those constants for an explanation of this setting.
352       *
353       * @return The current strength setting.
354       */
355      public synchronized int getStrength ()
356      {
357        return strength;
358      }
359    
360      /**
361       * This method returns a hash code value for this object.
362       *
363       * @return A hash value for this object.
364       */
365      public abstract int hashCode ();
366    
367      /**
368       * This method sets the decomposition setting for this object to the
369       * specified value.  This must be one of NO_DECOMPOSITION,
370       * CANONICAL_DECOMPOSITION, or FULL_DECOMPOSITION.  Otherwise an
371       * exception will be thrown.  See the documentation for those
372       * contants for an explanation of this setting.
373       *
374       * @param mode The new decomposition setting.
375       *
376       * @exception IllegalArgumentException If the requested
377       * decomposition setting is not valid.
378       */
379      public synchronized void setDecomposition (int mode)
380      {
381        if (mode != NO_DECOMPOSITION
382            && mode != CANONICAL_DECOMPOSITION
383            && mode != FULL_DECOMPOSITION)
384          throw new IllegalArgumentException ();
385        decmp = mode;
386      }
387    
388      /**
389       * This method sets the strength setting for this object to the specified
390       * value.  This must be one of PRIMARY, SECONDARY, TERTIARY, or IDENTICAL.
391       * Otherwise an exception is thrown. See the documentation for these
392       * constants for an explanation of this setting.
393       * 
394       * @param strength The new strength setting.
395       *
396       * @exception IllegalArgumentException If the requested strength
397       * setting value is not valid.
398       */
399      public synchronized void setStrength (int strength)
400      {
401        if (strength != PRIMARY && strength != SECONDARY
402            && strength != TERTIARY && strength != IDENTICAL)
403          throw new IllegalArgumentException ();
404        this.strength = strength;
405      }
406    
407      // Decompose a single character and append results to the buffer.
408      native final void decomposeCharacter (char c, StringBuffer buf);
409    
410      /**
411       * This is the current collation decomposition setting.
412       */
413      int decmp;
414    
415      /**
416       * This is the current collation strength setting.
417       */
418      int strength;
419    }