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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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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
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15 * accompanied this code).
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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
39package java.text;
40
41import 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 id="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 * @since 1.1
133 */
134public abstract class Format implements Serializable, Cloneable {
135
136    private static final long serialVersionUID = -299282585814624189L;
137
138    /**
139     * Sole constructor.  (For invocation by subclass constructors, typically
140     * implicit.)
141     */
142    protected Format() {
143    }
144
145    /**
146     * Formats an object to produce a string. This is equivalent to
147     * <blockquote>
148     * {@link #format(Object, StringBuffer, FieldPosition) format}<code>(obj,
149     *         new StringBuffer(), new FieldPosition(0)).toString();</code>
150     * </blockquote>
151     *
152     * @param obj    The object to format
153     * @return       Formatted string.
154     * @exception IllegalArgumentException if the Format cannot format the given
155     *            object
156     */
157    public final String format (Object obj) {
158        return format(obj, new StringBuffer(), new FieldPosition(0)).toString();
159    }
160
161    /**
162     * Formats an object and appends the resulting text to a given string
163     * buffer.
164     * If the <code>pos</code> argument identifies a field used by the format,
165     * then its indices are set to the beginning and end of the first such
166     * field encountered.
167     *
168     * @param obj    The object to format
169     * @param toAppendTo    where the text is to be appended
170     * @param pos    A <code>FieldPosition</code> identifying a field
171     *               in the formatted text
172     * @return       the string buffer passed in as <code>toAppendTo</code>,
173     *               with formatted text appended
174     * @exception NullPointerException if <code>toAppendTo</code> or
175     *            <code>pos</code> is null
176     * @exception IllegalArgumentException if the Format cannot format the given
177     *            object
178     */
179    public abstract StringBuffer format(Object obj,
180                    StringBuffer toAppendTo,
181                    FieldPosition pos);
182
183    /**
184     * Formats an Object producing an <code>AttributedCharacterIterator</code>.
185     * You can use the returned <code>AttributedCharacterIterator</code>
186     * to build the resulting String, as well as to determine information
187     * about the resulting String.
188     * <p>
189     * Each attribute key of the AttributedCharacterIterator will be of type
190     * <code>Field</code>. It is up to each <code>Format</code> implementation
191     * to define what the legal values are for each attribute in the
192     * <code>AttributedCharacterIterator</code>, but typically the attribute
193     * key is also used as the attribute value.
194     * <p>The default implementation creates an
195     * <code>AttributedCharacterIterator</code> with no attributes. Subclasses
196     * that support fields should override this and create an
197     * <code>AttributedCharacterIterator</code> with meaningful attributes.
198     *
199     * @exception NullPointerException if obj is null.
200     * @exception IllegalArgumentException when the Format cannot format the
201     *            given object.
202     * @param obj The object to format
203     * @return AttributedCharacterIterator describing the formatted value.
204     * @since 1.4
205     */
206    public AttributedCharacterIterator formatToCharacterIterator(Object obj) {
207        return createAttributedCharacterIterator(format(obj));
208    }
209
210    /**
211     * Parses text from a string to produce an object.
212     * <p>
213     * The method attempts to parse text starting at the index given by
214     * <code>pos</code>.
215     * If parsing succeeds, then the index of <code>pos</code> is updated
216     * to the index after the last character used (parsing does not necessarily
217     * use all characters up to the end of the string), and the parsed
218     * object is returned. The updated <code>pos</code> can be used to
219     * indicate the starting point for the next call to this method.
220     * If an error occurs, then the index of <code>pos</code> is not
221     * changed, the error index of <code>pos</code> is set to the index of
222     * the character where the error occurred, and null is returned.
223     *
224     * @param source A <code>String</code>, part of which should be parsed.
225     * @param pos A <code>ParsePosition</code> object with index and error
226     *            index information as described above.
227     * @return An <code>Object</code> parsed from the string. In case of
228     *         error, returns null.
229     * @throws NullPointerException if {@code source} or {@code pos} is null.
230     */
231    public abstract Object parseObject (String source, ParsePosition pos);
232
233    /**
234     * Parses text from the beginning of the given string to produce an object.
235     * The method may not use the entire text of the given string.
236     *
237     * @param source A <code>String</code> whose beginning should be parsed.
238     * @return An <code>Object</code> parsed from the string.
239     * @exception ParseException if the beginning of the specified string
240     *            cannot be parsed.
241     * @throws NullPointerException if {@code source} is null.
242     */
243    public Object parseObject(String source) throws ParseException {
244        ParsePosition pos = new ParsePosition(0);
245        Object result = parseObject(source, pos);
246        if (pos.index == 0) {
247            throw new ParseException("Format.parseObject(String) failed",
248                pos.errorIndex);
249        }
250        return result;
251    }
252
253    /**
254     * Creates and returns a copy of this object.
255     *
256     * @return a clone of this instance.
257     */
258    public Object clone() {
259        try {
260            return super.clone();
261        } catch (CloneNotSupportedException e) {
262            // will never happen
263            throw new InternalError(e);
264        }
265    }
266
267    //
268    // Convenience methods for creating AttributedCharacterIterators from
269    // different parameters.
270    //
271
272    /**
273     * Creates an <code>AttributedCharacterIterator</code> for the String
274     * <code>s</code>.
275     *
276     * @param s String to create AttributedCharacterIterator from
277     * @return AttributedCharacterIterator wrapping s
278     */
279    AttributedCharacterIterator createAttributedCharacterIterator(String s) {
280        AttributedString as = new AttributedString(s);
281
282        return as.getIterator();
283    }
284
285    /**
286     * Creates an <code>AttributedCharacterIterator</code> containing the
287     * concatenated contents of the passed in
288     * <code>AttributedCharacterIterator</code>s.
289     *
290     * @param iterators AttributedCharacterIterators used to create resulting
291     *                  AttributedCharacterIterators
292     * @return AttributedCharacterIterator wrapping passed in
293     *         AttributedCharacterIterators
294     */
295    AttributedCharacterIterator createAttributedCharacterIterator(
296                       AttributedCharacterIterator[] iterators) {
297        AttributedString as = new AttributedString(iterators);
298
299        return as.getIterator();
300    }
301
302    /**
303     * Returns an AttributedCharacterIterator with the String
304     * <code>string</code> and additional key/value pair <code>key</code>,
305     * <code>value</code>.
306     *
307     * @param string String to create AttributedCharacterIterator from
308     * @param key Key for AttributedCharacterIterator
309     * @param value Value associated with key in AttributedCharacterIterator
310     * @return AttributedCharacterIterator wrapping args
311     */
312    AttributedCharacterIterator createAttributedCharacterIterator(
313                      String string, AttributedCharacterIterator.Attribute key,
314                      Object value) {
315        AttributedString as = new AttributedString(string);
316
317        as.addAttribute(key, value);
318        return as.getIterator();
319    }
320
321    /**
322     * Creates an AttributedCharacterIterator with the contents of
323     * <code>iterator</code> and the additional attribute <code>key</code>
324     * <code>value</code>.
325     *
326     * @param iterator Initial AttributedCharacterIterator to add arg to
327     * @param key Key for AttributedCharacterIterator
328     * @param value Value associated with key in AttributedCharacterIterator
329     * @return AttributedCharacterIterator wrapping args
330     */
331    AttributedCharacterIterator createAttributedCharacterIterator(
332              AttributedCharacterIterator iterator,
333              AttributedCharacterIterator.Attribute key, Object value) {
334        AttributedString as = new AttributedString(iterator);
335
336        as.addAttribute(key, value);
337        return as.getIterator();
338    }
339
340
341    /**
342     * Defines constants that are used as attribute keys in the
343     * <code>AttributedCharacterIterator</code> returned
344     * from <code>Format.formatToCharacterIterator</code> and as
345     * field identifiers in <code>FieldPosition</code>.
346     *
347     * @since 1.4
348     */
349    public static class Field extends AttributedCharacterIterator.Attribute {
350
351        // Proclaim serial compatibility with 1.4 FCS
352        private static final long serialVersionUID = 276966692217360283L;
353
354        /**
355         * Creates a Field with the specified name.
356         *
357         * @param name Name of the attribute
358         */
359        protected Field(String name) {
360            super(name);
361        }
362    }
363
364
365    /**
366     * FieldDelegate is notified by the various <code>Format</code>
367     * implementations as they are formatting the Objects. This allows for
368     * storage of the individual sections of the formatted String for
369     * later use, such as in a <code>FieldPosition</code> or for an
370     * <code>AttributedCharacterIterator</code>.
371     * <p>
372     * Delegates should NOT assume that the <code>Format</code> will notify
373     * the delegate of fields in any particular order.
374     *
375     * @see FieldPosition#getFieldDelegate
376     * @see CharacterIteratorFieldDelegate
377     */
378    interface FieldDelegate {
379        /**
380         * Notified when a particular region of the String is formatted. This
381         * method will be invoked if there is no corresponding integer field id
382         * matching <code>attr</code>.
383         *
384         * @param attr Identifies the field matched
385         * @param value Value associated with the field
386         * @param start Beginning location of the field, will be >= 0
387         * @param end End of the field, will be >= start and <= buffer.length()
388         * @param buffer Contains current formatted value, receiver should
389         *        NOT modify it.
390         */
391        public void formatted(Format.Field attr, Object value, int start,
392                              int end, StringBuffer buffer);
393
394        /**
395         * Notified when a particular region of the String is formatted.
396         *
397         * @param fieldID Identifies the field by integer
398         * @param attr Identifies the field matched
399         * @param value Value associated with the field
400         * @param start Beginning location of the field, will be >= 0
401         * @param end End of the field, will be >= start and <= buffer.length()
402         * @param buffer Contains current formatted value, receiver should
403         *        NOT modify it.
404         */
405        public void formatted(int fieldID, Format.Field attr, Object value,
406                              int start, int end, StringBuffer buffer);
407    }
408}
409