libjava/java/text/BreakIterator.java

   1 /* BreakIterator.java -- Breaks text into elements
   2    Copyright (C) 1998, 1999, 2001 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., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 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.Locale;
  42 import java.util.MissingResourceException;
  43 import java.util.ResourceBundle;
  44
  45 /**
  46  * This class iterates over text elements such as words, lines, sentences,
  47  * and characters.  It can only iterate over one of these text elements at
  48  * a time.  An instance of this class configured for the desired iteration
  49  * type is created by calling one of the static factory methods, not
  50  * by directly calling a constructor.
  51  *
  52  * @author Tom Tromey <tromey@cygnus.com>
  53  * @author Aaron M. Renn (arenn@urbanophile.com)
  54  * @date March 19, 1999
  55  */
  56 /* Written using "Java Class Libraries", 2nd edition, plus online
  57  * API docs for JDK 1.2 beta from http://www.javasoft.com.
  58  * Status:  Believed complete and correct to 1.1.
  59  */
  60 public abstract class BreakIterator implements Cloneable
  61 {
  62   /**
  63    * This value is returned by the <code>next()</code> and
  64    * <code>previous</code> in order to indicate that the end of the
  65    * text has been reached.
  66    */
  67   // The value was discovered by writing a test program.
  68   public static final int DONE = -1;
  69
  70   /**
  71    * This method initializes a new instance of <code>BreakIterator</code>.
  72    * This protected constructor is available to subclasses as a default
  73    * no-arg superclass constructor.
  74    */
  75   protected BreakIterator ()
  76   {
  77   }
  78
  79   /**
  80    * This method returns the index of the current text element boundary.
  81    *
  82    * @return The current text boundary.
  83    */
  84   public abstract int current ();
  85
  86   /**
  87    * This method returns the first text element boundary in the text being
  88    * iterated over.
  89    *
  90    * @return The first text boundary.
  91    */
  92   public abstract int first ();
  93
  94   /**
  95    * This methdod returns the offset of the text element boundary following
  96    * the specified offset.
  97    *
  98    * @param offset The text index from which to find the next text boundary.
  99    *
 100    * @param The next text boundary following the specified index.
 101    */
 102   public abstract int following (int pos);
 103
 104   /**
 105    * This method returns a list of locales for which instances of
 106    * <code>BreakIterator</code> are available.
 107    *
 108    * @return A list of available locales
 109    */
 110   public static synchronized Locale[] getAvailableLocales ()
 111   {
 112     Locale[] l = new Locale[1];
 113     l[0] = Locale.US;
 114     return l;
 115   }
 116
 117   private static BreakIterator getInstance (String type, Locale loc)
 118   {
 119     String className;
 120     try
 121       {
 122         ResourceBundle res
 123           = ResourceBundle.getBundle("gnu.java.locale.LocaleInformation",
 124                                      loc);
 125         className = res.getString(type);
 126       }
 127     catch (MissingResourceException x)
 128       {
 129         return null;
 130       }
 131     try
 132       {
 133         Class k = Class.forName(className);
 134         return (BreakIterator) k.newInstance();
 135       }
 136     catch (ClassNotFoundException x1)
 137       {
 138         return null;
 139       }
 140     catch (InstantiationException x2)
 141       {
 142         return null;
 143       }
 144     catch (IllegalAccessException x3)
 145       {
 146         return null;
 147       }
 148   }
 149
 150   /**
 151    * This method returns an instance of <code>BreakIterator</code> that will
 152    * iterate over characters as defined in the default locale.
 153    *
 154    * @return A <code>BreakIterator</code> instance for the default locale.
 155    */
 156   public static BreakIterator getCharacterInstance ()
 157   {
 158     return getCharacterInstance (Locale.getDefault());
 159   }
 160
 161   /**
 162    * This method returns an instance of <code>BreakIterator</code> that will
 163    * iterate over characters as defined in the specified locale.  If the
 164    * desired locale is not available, the default locale is used.
 165    *
 166    * @param locale The desired locale.
 167    *
 168    * @return A <code>BreakIterator</code> instance for the default locale.
 169    */
 170   public static BreakIterator getCharacterInstance (Locale loc)
 171   {
 172     BreakIterator r = getInstance ("CharacterIterator", loc);
 173     if (r == null)
 174       r = new gnu.java.text.CharacterBreakIterator ();
 175     return r;
 176   }
 177
 178   /**
 179    * This method returns an instance of <code>BreakIterator</code> that will
 180    * iterate over line breaks as defined in the default locale.
 181    *
 182    * @return A <code>BreakIterator</code> instance for the default locale.
 183    */
 184   public static BreakIterator getLineInstance ()
 185   {
 186     return getLineInstance (Locale.getDefault());
 187   }
 188
 189   /**
 190    * This method returns an instance of <code>BreakIterator</code> that will
 191    * iterate over line breaks as defined in the specified locale.  If the
 192    * desired locale is not available, the default locale is used.
 193    *
 194    * @param locale The desired locale.
 195    *
 196    * @return A <code>BreakIterator</code> instance for the default locale.
 197    */
 198   public static BreakIterator getLineInstance (Locale loc)
 199   {
 200     BreakIterator r = getInstance ("LineIterator", loc);
 201     if (r == null)
 202       r = new gnu.java.text.LineBreakIterator ();
 203     return r;
 204   }
 205
 206   /**
 207    * This method returns an instance of <code>BreakIterator</code> that will
 208    * iterate over sentences as defined in the default locale.
 209    *
 210    * @return A <code>BreakIterator</code> instance for the default locale.
 211    */
 212   public static BreakIterator getSentenceInstance ()
 213   {
 214     return getSentenceInstance (Locale.getDefault());
 215   }
 216
 217   /**
 218    * This method returns an instance of <code>BreakIterator</code> that will
 219    * iterate over sentences as defined in the specified locale.  If the
 220    * desired locale is not available, the default locale is used.
 221    *
 222    * @param locale The desired locale.
 223    *
 224    * @return A <code>BreakIterator</code> instance for the default locale.
 225    */
 226   public static BreakIterator getSentenceInstance (Locale loc)
 227   {
 228     BreakIterator r = getInstance ("SentenceIterator", loc);
 229     if (r == null)
 230       r = new gnu.java.text.SentenceBreakIterator ();
 231     return r;
 232   }
 233
 234   /**
 235    * This method returns the text this object is iterating over as a
 236    * <code>CharacterIterator</code>.
 237    *
 238    * @param The text being iterated over.
 239    */
 240   public abstract CharacterIterator getText ();
 241
 242   /**
 243    * This method returns an instance of <code>BreakIterator</code> that will
 244    * iterate over words as defined in the default locale.
 245    *
 246    * @return A <code>BreakIterator</code> instance for the default locale.
 247    */
 248   public static BreakIterator getWordInstance ()
 249   {
 250     return getWordInstance (Locale.getDefault());
 251   }
 252
 253   /**
 254    * This method returns an instance of <code>BreakIterator</code> that will
 255    * iterate over words as defined in the specified locale.  If the
 256    * desired locale is not available, the default locale is used.
 257    *
 258    * @param locale The desired locale.
 259    *
 260    * @return A <code>BreakIterator</code> instance for the default locale.
 261    */
 262   public static BreakIterator getWordInstance (Locale loc)
 263   {
 264     BreakIterator r = getInstance ("WordIterator", loc);
 265     if (r == null)
 266       r = new gnu.java.text.WordBreakIterator ();
 267     return r;
 268   }
 269
 270   /**
 271    * This method tests whether or not the specified position is a text
 272    * element boundary.
 273    *
 274    * @param offset The text position to test.
 275    *
 276    * @return <code>true</code> if the position is a boundary,
 277    * <code>false</code> otherwise.
 278    */
 279   public boolean isBoundary (int pos)
 280   {
 281     if (pos == 0)
 282       return true;
 283     return following (pos - 1) == pos;
 284   }
 285
 286   /**
 287    * This method returns the last text element boundary in the text being
 288    * iterated over.
 289    *
 290    * @return The last text boundary.
 291    */
 292   public abstract int last ();
 293
 294   /**
 295    * This method returns the text element boundary following the current
 296    * text position.
 297    *
 298    * @return The next text boundary.
 299    */
 300   public abstract int next ();
 301
 302   /**
 303    * This method returns the n'th text element boundary following the current
 304    * text position.
 305    *
 306    * @param n The number of text element boundaries to skip.
 307    *
 308    * @return The next text boundary.
 309    */
 310   public abstract int next (int n);
 311
 312   /**
 313    * This methdod returns the offset of the text element boundary preceding
 314    * the specified offset.
 315    *
 316    * @param offset The text index from which to find the preceding
 317    *               text boundary.
 318    *
 319    * @returns The next text boundary preceding the specified index.
 320    */
 321   public int preceding (int pos)
 322   {
 323     if (following (pos) == DONE)
 324       last ();
 325     while (previous () >= pos)
 326       ;
 327     return current ();
 328   }
 329
 330   /**
 331    * This method returns the text element boundary preceding the current
 332    * text position.
 333    *
 334    * @return The previous text boundary.
 335    */
 336   public abstract int previous ();
 337
 338   /**
 339    * This method sets the text string to iterate over.
 340    *
 341    * @param str The <code>String</code> to iterate over.
 342    */
 343   public void setText (String newText)
 344   {
 345     setText (new StringCharacterIterator (newText));
 346   }
 347
 348   /**
 349    * This method sets the text to iterate over from the specified
 350    * <code>CharacterIterator</code>.
 351    *
 352    * @param ci The desired <code>CharacterIterator</code>.
 353    */
 354   public abstract void setText (CharacterIterator newText);
 355 }