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17 package org.apache.commons.math.fraction;
18
19 import java.io.Serializable;
20 import java.text.FieldPosition;
21 import java.text.Format;
22 import java.text.NumberFormat;
23 import java.text.ParseException;
24 import java.text.ParsePosition;
25 import java.util.Locale;
26
27 import org.apache.commons.math.ConvergenceException;
28
29 /**
30 * Formats a Fraction number in proper format or improper format. The number
31 * format for each of the whole number, numerator and, denominator can be
32 * configured.
33 *
34 * @since 1.1
35 * @version $Revision: 348519 $ $Date: 2005-11-23 12:12:18 -0700 (Wed, 23 Nov 2005) $
36 */
37 public class FractionFormat extends Format implements Serializable {
38
39 /** Serializable version identifier */
40 private static final long serialVersionUID = -6337346779577272306L;
41
42 /** The format used for the denominator. */
43 private NumberFormat denominatorFormat;
44
45 /** The format used for the numerator. */
46 private NumberFormat numeratorFormat;
47
48 /**
49 * Create an improper formatting instance with the default number format
50 * for the numerator and denominator.
51 */
52 public FractionFormat() {
53 this(getDefaultNumberFormat());
54 }
55
56 /**
57 * Create an improper formatting instance with a custom number format for
58 * both the numerator and denominator.
59 * @param format the custom format for both the numerator and denominator.
60 */
61 public FractionFormat(NumberFormat format) {
62 this(format, (NumberFormat)format.clone());
63 }
64
65 /**
66 * Create an improper formatting instance with a custom number format for
67 * the numerator and a custom number format for the denominator.
68 * @param numeratorFormat the custom format for the numerator.
69 * @param denominatorFormat the custom format for the denominator.
70 */
71 public FractionFormat(NumberFormat numeratorFormat,
72 NumberFormat denominatorFormat)
73 {
74 super();
75 this.numeratorFormat = numeratorFormat;
76 this.denominatorFormat = denominatorFormat;
77 }
78
79 /**
80 * This static method calls formatFraction() on a default instance of
81 * FractionFormat.
82 *
83 * @param f Fraction object to format
84 * @return A formatted fraction in proper form.
85 */
86 public static String formatFraction(Fraction f) {
87 return getImproperInstance().format(f);
88 }
89
90 /**
91 * Get the set of locales for which complex formats are available. This
92 * is the same set as the {@link NumberFormat} set.
93 * @return available complex format locales.
94 */
95 public static Locale[] getAvailableLocales() {
96 return NumberFormat.getAvailableLocales();
97 }
98
99 /**
100 * Returns the default complex format for the current locale.
101 * @return the default complex format.
102 */
103 public static FractionFormat getImproperInstance() {
104 return getImproperInstance(Locale.getDefault());
105 }
106
107 /**
108 * Returns the default complex format for the given locale.
109 * @param locale the specific locale used by the format.
110 * @return the complex format specific to the given locale.
111 */
112 public static FractionFormat getImproperInstance(Locale locale) {
113 NumberFormat f = getDefaultNumberFormat(locale);
114 return new FractionFormat(f);
115 }
116
117 /**
118 * Returns the default complex format for the current locale.
119 * @return the default complex format.
120 */
121 public static FractionFormat getProperInstance() {
122 return getProperInstance(Locale.getDefault());
123 }
124
125 /**
126 * Returns the default complex format for the given locale.
127 * @param locale the specific locale used by the format.
128 * @return the complex format specific to the given locale.
129 */
130 public static FractionFormat getProperInstance(Locale locale) {
131 NumberFormat f = getDefaultNumberFormat(locale);
132 return new ProperFractionFormat(f);
133 }
134
135 /**
136 * Create a default number format. The default number format is based on
137 * {@link NumberFormat#getNumberInstance(java.util.Locale)} with the only
138 * customizing is the maximum number of fraction digits, which is set to 0.
139 * @return the default number format.
140 */
141 protected static NumberFormat getDefaultNumberFormat() {
142 return getDefaultNumberFormat(Locale.getDefault());
143 }
144
145 /**
146 * Create a default number format. The default number format is based on
147 * {@link NumberFormat#getNumberInstance(java.util.Locale)} with the only
148 * customizing is the maximum number of fraction digits, which is set to 0.
149 * @param locale the specific locale used by the format.
150 * @return the default number format specific to the given locale.
151 */
152 private static NumberFormat getDefaultNumberFormat(Locale locale) {
153 NumberFormat nf = NumberFormat.getNumberInstance(locale);
154 nf.setMaximumFractionDigits(0);
155 nf.setParseIntegerOnly(true);
156 return nf;
157 }
158
159 /**
160 * Formats a {@link Fraction} object to produce a string. The fraction is
161 * output in improper format.
162 *
163 * @param fraction the object to format.
164 * @param toAppendTo where the text is to be appended
165 * @param pos On input: an alignment field, if desired. On output: the
166 * offsets of the alignment field
167 * @return the value passed in as toAppendTo.
168 */
169 public StringBuffer format(Fraction fraction, StringBuffer toAppendTo,
170 FieldPosition pos) {
171
172 pos.setBeginIndex(0);
173 pos.setEndIndex(0);
174
175 getNumeratorFormat().format(fraction.getNumerator(), toAppendTo, pos);
176 toAppendTo.append(" / ");
177 getDenominatorFormat().format(fraction.getDenominator(), toAppendTo,
178 pos);
179
180 return toAppendTo;
181 }
182
183 /**
184 * Formats a object to produce a string. <code>obj</code> must be either a
185 * {@link Fraction} object or a {@link Number} object. Any other type of
186 * object will result in an {@link IllegalArgumentException} being thrown.
187 *
188 * @param obj the object to format.
189 * @param toAppendTo where the text is to be appended
190 * @param pos On input: an alignment field, if desired. On output: the
191 * offsets of the alignment field
192 * @return the value passed in as toAppendTo.
193 * @see java.text.Format#format(java.lang.Object, java.lang.StringBuffer, java.text.FieldPosition)
194 * @throws IllegalArgumentException is <code>obj</code> is not a valid type.
195 */
196 public StringBuffer format(Object obj, StringBuffer toAppendTo,
197 FieldPosition pos)
198 {
199 StringBuffer ret = null;
200
201 if (obj instanceof Fraction) {
202 ret = format( (Fraction)obj, toAppendTo, pos);
203 } else if (obj instanceof Number) {
204 try {
205 ret = format( new Fraction(((Number)obj).doubleValue()),
206 toAppendTo, pos);
207 } catch (ConvergenceException ex) {
208 throw new IllegalArgumentException(
209 "Cannot convert given object to a fraction.");
210 }
211 } else {
212 throw new IllegalArgumentException(
213 "Cannot format given object as a fraction");
214 }
215
216 return ret;
217 }
218
219 /**
220 * Access the denominator format.
221 * @return the denominator format.
222 */
223 public NumberFormat getDenominatorFormat() {
224 return denominatorFormat;
225 }
226
227 /**
228 * Access the numerator format.
229 * @return the numerator format.
230 */
231 public NumberFormat getNumeratorFormat() {
232 return numeratorFormat;
233 }
234
235 /**
236 * Parses a string to produce a {@link Fraction} object.
237 * @param source the string to parse
238 * @return the parsed {@link Fraction} object.
239 * @exception ParseException if the beginning of the specified string
240 * cannot be parsed.
241 */
242 public Fraction parse(String source) throws ParseException {
243 ParsePosition parsePosition = new ParsePosition(0);
244 Fraction result = parse(source, parsePosition);
245 if (parsePosition.getIndex() == 0) {
246 throw new ParseException("Unparseable fraction number: \"" +
247 source + "\"", parsePosition.getErrorIndex());
248 }
249 return result;
250 }
251
252 /**
253 * Parses a string to produce a {@link Fraction} object. This method
254 * expects the string to be formatted as an improper fraction.
255 * @param source the string to parse
256 * @param pos input/ouput parsing parameter.
257 * @return the parsed {@link Fraction} object.
258 */
259 public Fraction parse(String source, ParsePosition pos) {
260 int initialIndex = pos.getIndex();
261
262
263 parseAndIgnoreWhitespace(source, pos);
264
265
266 Number num = getNumeratorFormat().parse(source, pos);
267 if (num == null) {
268
269
270
271 pos.setIndex(initialIndex);
272 return null;
273 }
274
275
276 int startIndex = pos.getIndex();
277 char c = parseNextCharacter(source, pos);
278 switch (c) {
279 case 0 :
280
281
282 return new Fraction(num.intValue(), 1);
283 case '/' :
284
285 break;
286 default :
287
288
289
290 pos.setIndex(initialIndex);
291 pos.setErrorIndex(startIndex);
292 return null;
293 }
294
295
296 parseAndIgnoreWhitespace(source, pos);
297
298
299 Number den = getDenominatorFormat().parse(source, pos);
300 if (den == null) {
301
302
303
304 pos.setIndex(initialIndex);
305 return null;
306 }
307
308 return new Fraction(num.intValue(), den.intValue());
309 }
310
311 /**
312 * Parses a string to produce a object.
313 * @param source the string to parse
314 * @param pos input/ouput parsing parameter.
315 * @return the parsed object.
316 * @see java.text.Format#parseObject(java.lang.String, java.text.ParsePosition)
317 */
318 public Object parseObject(String source, ParsePosition pos) {
319 return parse(source, pos);
320 }
321
322 /**
323 * Modify the denominator format.
324 * @param format the new denominator format value.
325 * @throws IllegalArgumentException if <code>format</code> is
326 * <code>null</code>.
327 */
328 public void setDenominatorFormat(NumberFormat format) {
329 if (format == null) {
330 throw new IllegalArgumentException(
331 "denominator format can not be null.");
332 }
333 this.denominatorFormat = format;
334 }
335
336 /**
337 * Modify the numerator format.
338 * @param format the new numerator format value.
339 * @throws IllegalArgumentException if <code>format</code> is
340 * <code>null</code>.
341 */
342 public void setNumeratorFormat(NumberFormat format) {
343 if (format == null) {
344 throw new IllegalArgumentException(
345 "numerator format can not be null.");
346 }
347 this.numeratorFormat = format;
348 }
349
350 /**
351 * Parses <code>source</code> until a non-whitespace character is found.
352 * @param source the string to parse
353 * @param pos input/ouput parsing parameter. On output, <code>pos</code>
354 * holds the index of the next non-whitespace character.
355 */
356 protected static void parseAndIgnoreWhitespace(
357 String source, ParsePosition pos)
358 {
359 parseNextCharacter(source, pos);
360 pos.setIndex(pos.getIndex() - 1);
361 }
362
363 /**
364 * Parses <code>source</code> until a non-whitespace character is found.
365 * @param source the string to parse
366 * @param pos input/ouput parsing parameter.
367 * @return the first non-whitespace character.
368 */
369 protected static char parseNextCharacter(String source, ParsePosition pos) {
370 int index = pos.getIndex();
371 int n = source.length();
372 char ret = 0;
373
374 if (index < n) {
375 char c;
376 do {
377 c = source.charAt(index++);
378 } while (Character.isWhitespace(c) && index < n);
379 pos.setIndex(index);
380
381 if (index < n) {
382 ret = c;
383 }
384 }
385
386 return ret;
387 }
388 }