1 /*
   2  * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
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  25 
  26 /*
  27  * (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved
  28  * (C) Copyright IBM Corp. 1996 - 1998 - All Rights Reserved
  29  *
  30  *   The original version of this source code and documentation is copyrighted
  31  * and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These
  32  * materials are provided under terms of a License Agreement between Taligent
  33  * and Sun. This technology is protected by multiple US and International
  34  * patents. This notice and attribution to Taligent may not be removed.
  35  *   Taligent is a registered trademark of Taligent, Inc.
  36  *
  37  */
  38 
  39 package java.text;
  40 
  41 import java.io.Serializable;
  42 
  43 /**
  44  * <code>Format</code> is an abstract base class for formatting locale-sensitive
  45  * information such as dates, messages, and numbers.
  46  *
  47  * <p>
  48  * <code>Format</code> defines the programming interface for formatting
  49  * locale-sensitive objects into <code>String</code>s (the
  50  * <code>format</code> method) and for parsing <code>String</code>s back
  51  * into objects (the <code>parseObject</code> method).
  52  *
  53  * <p>
  54  * Generally, a format's <code>parseObject</code> method must be able to parse
  55  * any string formatted by its <code>format</code> method. However, there may
  56  * be exceptional cases where this is not possible. For example, a
  57  * <code>format</code> method might create two adjacent integer numbers with
  58  * no separator in between, and in this case the <code>parseObject</code> could
  59  * not tell which digits belong to which number.
  60  *
  61  * <h3>Subclassing</h3>
  62  *
  63  * <p>
  64  * The Java Platform provides three specialized subclasses of <code>Format</code>--
  65  * <code>DateFormat</code>, <code>MessageFormat</code>, and
  66  * <code>NumberFormat</code>--for formatting dates, messages, and numbers,
  67  * respectively.
  68  * <p>
  69  * Concrete subclasses must implement three methods:
  70  * <ol>
  71  * <li> <code>format(Object obj, StringBuffer toAppendTo, FieldPosition pos)</code>
  72  * <li> <code>formatToCharacterIterator(Object obj)</code>
  73  * <li> <code>parseObject(String source, ParsePosition pos)</code>
  74  * </ol>
  75  * These general methods allow polymorphic parsing and formatting of objects
  76  * and are used, for example, by <code>MessageFormat</code>.
  77  * Subclasses often also provide additional <code>format</code> methods for
  78  * specific input types as well as <code>parse</code> methods for specific
  79  * result types. Any <code>parse</code> method that does not take a
  80  * <code>ParsePosition</code> argument should throw <code>ParseException</code>
  81  * when no text in the required format is at the beginning of the input text.
  82  *
  83  * <p>
  84  * Most subclasses will also implement the following factory methods:
  85  * <ol>
  86  * <li>
  87  * <code>getInstance</code> for getting a useful format object appropriate
  88  * for the current locale
  89  * <li>
  90  * <code>getInstance(Locale)</code> for getting a useful format
  91  * object appropriate for the specified locale
  92  * </ol>
  93  * In addition, some subclasses may also implement other
  94  * <code>getXxxxInstance</code> methods for more specialized control. For
  95  * example, the <code>NumberFormat</code> class provides
  96  * <code>getPercentInstance</code> and <code>getCurrencyInstance</code>
  97  * methods for getting specialized number formatters.
  98  *
  99  * <p>
 100  * Subclasses of <code>Format</code> that allow programmers to create objects
 101  * for locales (with <code>getInstance(Locale)</code> for example)
 102  * must also implement the following class method:
 103  * <blockquote>
 104  * <pre>
 105  * public static Locale[] getAvailableLocales()
 106  * </pre>
 107  * </blockquote>
 108  *
 109  * <p>
 110  * And finally subclasses may define a set of constants to identify the various
 111  * fields in the formatted output. These constants are used to create a FieldPosition
 112  * object which identifies what information is contained in the field and its
 113  * position in the formatted result. These constants should be named
 114  * <code><em>item</em>_FIELD</code> where <code><em>item</em></code> identifies
 115  * the field. For examples of these constants, see <code>ERA_FIELD</code> and its
 116  * friends in {@link DateFormat}.
 117  *
 118  * <h4><a name="synchronization">Synchronization</a></h4>
 119  *
 120  * <p>
 121  * Formats are generally not synchronized.
 122  * It is recommended to create separate format instances for each thread.
 123  * If multiple threads access a format concurrently, it must be synchronized
 124  * externally.
 125  *
 126  * @see          java.text.ParsePosition
 127  * @see          java.text.FieldPosition
 128  * @see          java.text.NumberFormat
 129  * @see          java.text.DateFormat
 130  * @see          java.text.MessageFormat
 131  * @author       Mark Davis
 132  */
 133 public abstract class Format implements Serializable, Cloneable {
 134 
 135     private static final long serialVersionUID = -299282585814624189L;
 136 
 137     /**
 138      * Sole constructor.  (For invocation by subclass constructors, typically
 139      * implicit.)
 140      */
 141     protected Format() {
 142     }
 143 
 144     /**
 145      * Formats an object to produce a string. This is equivalent to
 146      * <blockquote>
 147      * {@link #format(Object, StringBuffer, FieldPosition) format}<code>(obj,
 148      *         new StringBuffer(), new FieldPosition(0)).toString();</code>
 149      * </blockquote>
 150      *
 151      * @param obj    The object to format
 152      * @return       Formatted string.
 153      * @exception IllegalArgumentException if the Format cannot format the given
 154      *            object
 155      */
 156     public final String format (Object obj) {
 157         return format(obj, new StringBuffer(), new FieldPosition(0)).toString();
 158     }
 159 
 160     /**
 161      * Formats an object and appends the resulting text to a given string
 162      * buffer.
 163      * If the <code>pos</code> argument identifies a field used by the format,
 164      * then its indices are set to the beginning and end of the first such
 165      * field encountered.
 166      *
 167      * @param obj    The object to format
 168      * @param toAppendTo    where the text is to be appended
 169      * @param pos    A <code>FieldPosition</code> identifying a field
 170      *               in the formatted text
 171      * @return       the string buffer passed in as <code>toAppendTo</code>,
 172      *               with formatted text appended
 173      * @exception NullPointerException if <code>toAppendTo</code> or
 174      *            <code>pos</code> is null
 175      * @exception IllegalArgumentException if the Format cannot format the given
 176      *            object
 177      */
 178     public abstract StringBuffer format(Object obj,
 179                     StringBuffer toAppendTo,
 180                     FieldPosition pos);
 181 
 182     /**
 183      * Formats an Object producing an <code>AttributedCharacterIterator</code>.
 184      * You can use the returned <code>AttributedCharacterIterator</code>
 185      * to build the resulting String, as well as to determine information
 186      * about the resulting String.
 187      * <p>
 188      * Each attribute key of the AttributedCharacterIterator will be of type
 189      * <code>Field</code>. It is up to each <code>Format</code> implementation
 190      * to define what the legal values are for each attribute in the
 191      * <code>AttributedCharacterIterator</code>, but typically the attribute
 192      * key is also used as the attribute value.
 193      * <p>The default implementation creates an
 194      * <code>AttributedCharacterIterator</code> with no attributes. Subclasses
 195      * that support fields should override this and create an
 196      * <code>AttributedCharacterIterator</code> with meaningful attributes.
 197      *
 198      * @exception NullPointerException if obj is null.
 199      * @exception IllegalArgumentException when the Format cannot format the
 200      *            given object.
 201      * @param obj The object to format
 202      * @return AttributedCharacterIterator describing the formatted value.
 203      * @since 1.4
 204      */
 205     public AttributedCharacterIterator formatToCharacterIterator(Object obj) {
 206         return createAttributedCharacterIterator(format(obj));
 207     }
 208 
 209     /**
 210      * Parses text from a string to produce an object.
 211      * <p>
 212      * The method attempts to parse text starting at the index given by
 213      * <code>pos</code>.
 214      * If parsing succeeds, then the index of <code>pos</code> is updated
 215      * to the index after the last character used (parsing does not necessarily
 216      * use all characters up to the end of the string), and the parsed
 217      * object is returned. The updated <code>pos</code> can be used to
 218      * indicate the starting point for the next call to this method.
 219      * If an error occurs, then the index of <code>pos</code> is not
 220      * changed, the error index of <code>pos</code> is set to the index of
 221      * the character where the error occurred, and null is returned.
 222      *
 223      * @param source A <code>String</code>, part of which should be parsed.
 224      * @param pos A <code>ParsePosition</code> object with index and error
 225      *            index information as described above.
 226      * @return An <code>Object</code> parsed from the string. In case of
 227      *         error, returns null.
 228      * @exception NullPointerException if <code>pos</code> is null.
 229      */
 230     public abstract Object parseObject (String source, ParsePosition pos);
 231 
 232     /**
 233      * Parses text from the beginning of the given string to produce an object.
 234      * The method may not use the entire text of the given string.
 235      *
 236      * @param source A <code>String</code> whose beginning should be parsed.
 237      * @return An <code>Object</code> parsed from the string.
 238      * @exception ParseException if the beginning of the specified string
 239      *            cannot be parsed.
 240      */
 241     public Object parseObject(String source) throws ParseException {
 242         ParsePosition pos = new ParsePosition(0);
 243         Object result = parseObject(source, pos);
 244         if (pos.index == 0) {
 245             throw new ParseException("Format.parseObject(String) failed",
 246                 pos.errorIndex);
 247         }
 248         return result;
 249     }
 250 
 251     /**
 252      * Creates and returns a copy of this object.
 253      *
 254      * @return a clone of this instance.
 255      */
 256     public Object clone() {
 257         try {
 258             return super.clone();
 259         } catch (CloneNotSupportedException e) {
 260             // will never happen
 261             throw new InternalError(e);
 262         }
 263     }
 264 
 265     //
 266     // Convenience methods for creating AttributedCharacterIterators from
 267     // different parameters.
 268     //
 269 
 270     /**
 271      * Creates an <code>AttributedCharacterIterator</code> for the String
 272      * <code>s</code>.
 273      *
 274      * @param s String to create AttributedCharacterIterator from
 275      * @return AttributedCharacterIterator wrapping s
 276      */
 277     AttributedCharacterIterator createAttributedCharacterIterator(String s) {
 278         AttributedString as = new AttributedString(s);
 279 
 280         return as.getIterator();
 281     }
 282 
 283     /**
 284      * Creates an <code>AttributedCharacterIterator</code> containing the
 285      * concatenated contents of the passed in
 286      * <code>AttributedCharacterIterator</code>s.
 287      *
 288      * @param iterators AttributedCharacterIterators used to create resulting
 289      *                  AttributedCharacterIterators
 290      * @return AttributedCharacterIterator wrapping passed in
 291      *         AttributedCharacterIterators
 292      */
 293     AttributedCharacterIterator createAttributedCharacterIterator(
 294                        AttributedCharacterIterator[] iterators) {
 295         AttributedString as = new AttributedString(iterators);
 296 
 297         return as.getIterator();
 298     }
 299 
 300     /**
 301      * Returns an AttributedCharacterIterator with the String
 302      * <code>string</code> and additional key/value pair <code>key</code>,
 303      * <code>value</code>.
 304      *
 305      * @param string String to create AttributedCharacterIterator from
 306      * @param key Key for AttributedCharacterIterator
 307      * @param value Value associated with key in AttributedCharacterIterator
 308      * @return AttributedCharacterIterator wrapping args
 309      */
 310     AttributedCharacterIterator createAttributedCharacterIterator(
 311                       String string, AttributedCharacterIterator.Attribute key,
 312                       Object value) {
 313         AttributedString as = new AttributedString(string);
 314 
 315         as.addAttribute(key, value);
 316         return as.getIterator();
 317     }
 318 
 319     /**
 320      * Creates an AttributedCharacterIterator with the contents of
 321      * <code>iterator</code> and the additional attribute <code>key</code>
 322      * <code>value</code>.
 323      *
 324      * @param iterator Initial AttributedCharacterIterator to add arg to
 325      * @param key Key for AttributedCharacterIterator
 326      * @param value Value associated with key in AttributedCharacterIterator
 327      * @return AttributedCharacterIterator wrapping args
 328      */
 329     AttributedCharacterIterator createAttributedCharacterIterator(
 330               AttributedCharacterIterator iterator,
 331               AttributedCharacterIterator.Attribute key, Object value) {
 332         AttributedString as = new AttributedString(iterator);
 333 
 334         as.addAttribute(key, value);
 335         return as.getIterator();
 336     }
 337 
 338 
 339     /**
 340      * Defines constants that are used as attribute keys in the
 341      * <code>AttributedCharacterIterator</code> returned
 342      * from <code>Format.formatToCharacterIterator</code> and as
 343      * field identifiers in <code>FieldPosition</code>.
 344      *
 345      * @since 1.4
 346      */
 347     public static class Field extends AttributedCharacterIterator.Attribute {
 348 
 349         // Proclaim serial compatibility with 1.4 FCS
 350         private static final long serialVersionUID = 276966692217360283L;
 351 
 352         /**
 353          * Creates a Field with the specified name.
 354          *
 355          * @param name Name of the attribute
 356          */
 357         protected Field(String name) {
 358             super(name);
 359         }
 360     }
 361 
 362 
 363     /**
 364      * FieldDelegate is notified by the various <code>Format</code>
 365      * implementations as they are formatting the Objects. This allows for
 366      * storage of the individual sections of the formatted String for
 367      * later use, such as in a <code>FieldPosition</code> or for an
 368      * <code>AttributedCharacterIterator</code>.
 369      * <p>
 370      * Delegates should NOT assume that the <code>Format</code> will notify
 371      * the delegate of fields in any particular order.
 372      *
 373      * @see FieldPosition#getFieldDelegate
 374      * @see CharacterIteratorFieldDelegate
 375      */
 376     interface FieldDelegate {
 377         /**
 378          * Notified when a particular region of the String is formatted. This
 379          * method will be invoked if there is no corresponding integer field id
 380          * matching <code>attr</code>.
 381          *
 382          * @param attr Identifies the field matched
 383          * @param value Value associated with the field
 384          * @param start Beginning location of the field, will be >= 0
 385          * @param end End of the field, will be >= start and <= buffer.length()
 386          * @param buffer Contains current formatted value, receiver should
 387          *        NOT modify it.
 388          */
 389         public void formatted(Format.Field attr, Object value, int start,
 390                               int end, StringBuffer buffer);
 391 
 392         /**
 393          * Notified when a particular region of the String is formatted.
 394          *
 395          * @param fieldID Identifies the field by integer
 396          * @param attr Identifies the field matched
 397          * @param value Value associated with the field
 398          * @param start Beginning location of the field, will be >= 0
 399          * @param end End of the field, will be >= start and <= buffer.length()
 400          * @param buffer Contains current formatted value, receiver should
 401          *        NOT modify it.
 402          */
 403         public void formatted(int fieldID, Format.Field attr, Object value,
 404                               int start, int end, StringBuffer buffer);
 405     }
 406 }