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Java > Open Source Codes > org > apache > commons > math > fraction > FractionFormat


1 /*
2  * Copyright 2005 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16
17 package org.apache.commons.math.fraction;
18
19 import java.io.Serializable JavaDoc;
20 import java.text.FieldPosition JavaDoc;
21 import java.text.Format JavaDoc;
22 import java.text.NumberFormat JavaDoc;
23 import java.text.ParseException JavaDoc;
24 import java.text.ParsePosition JavaDoc;
25 import java.util.Locale JavaDoc;
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 $Revision$ $Date: 2005-06-26 20:46:57 -0700 (Sun, 26 Jun 2005) $
36  */
37 public class FractionFormat extends Format JavaDoc implements Serializable JavaDoc {
38     
39     /** Serializable version identifier */
40     static final long serialVersionUID = -6337346779577272306L;
41
42     /** The format used for the denominator. */
43     private NumberFormat JavaDoc denominatorFormat;
44
45     /** The format used for the numerator. */
46     private NumberFormat JavaDoc 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 JavaDoc format) {
62         this(format, (NumberFormat JavaDoc)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 JavaDoc numeratorFormat,
72             NumberFormat JavaDoc 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 JavaDoc 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 JavaDoc[] 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 JavaDoc locale) {
113         NumberFormat JavaDoc 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 JavaDoc locale) {
131         NumberFormat JavaDoc 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 JavaDoc 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 JavaDoc getDefaultNumberFormat(Locale JavaDoc locale) {
153         NumberFormat JavaDoc 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 JavaDoc format(Fraction fraction, StringBuffer JavaDoc toAppendTo,
170             FieldPosition JavaDoc 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 JavaDoc format(Object JavaDoc obj, StringBuffer JavaDoc toAppendTo,
197             FieldPosition JavaDoc pos)
198     {
199         StringBuffer JavaDoc ret = null;
200         
201         if (obj instanceof Fraction) {
202             ret = format( (Fraction)obj, toAppendTo, pos);
203         } else if (obj instanceof Number JavaDoc) {
204             try {
205                 ret = format( new Fraction(((Number JavaDoc)obj).doubleValue()),
206                     toAppendTo, pos);
207             } catch (ConvergenceException ex) {
208                 throw new IllegalArgumentException JavaDoc(
209                     "Cannot convert given object to a fraction.");
210             }
211         } else {
212             throw new IllegalArgumentException JavaDoc(
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 JavaDoc getDenominatorFormat() {
224         return denominatorFormat;
225     }
226     
227     /**
228      * Access the numerator format.
229      * @return the numerator format.
230      */
231     public NumberFormat JavaDoc 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 JavaDoc source) throws ParseException JavaDoc {
243         ParsePosition JavaDoc parsePosition = new ParsePosition JavaDoc(0);
244         Fraction result = parse(source, parsePosition);
245         if (parsePosition.getIndex() == 0) {
246             throw new ParseException JavaDoc("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 JavaDoc source, ParsePosition JavaDoc pos) {
260         int initialIndex = pos.getIndex();
261
262         // parse whitespace
263 parseAndIgnoreWhitespace(source, pos);
264
265         // parse numerator
266 Number JavaDoc num = getNumeratorFormat().parse(source, pos);
267         if (num == null) {
268             // invalid integer number
269 // set index back to initial, error index should already be set
270 // character examined.
271 pos.setIndex(initialIndex);
272             return null;
273         }
274
275         // parse '/'
276 int startIndex = pos.getIndex();
277         char c = parseNextCharacter(source, pos);
278         switch (c) {
279         case 0 :
280             // no '/'
281 // return num as a fraction
282 return new Fraction(num.intValue(), 1);
283         case '/' :
284             // found '/', continue parsing denominator
285 break;
286         default :
287             // invalid '/'
288 // set index back to initial, error index should be the last
289 // character examined.
290 pos.setIndex(initialIndex);
291             pos.setErrorIndex(startIndex);
292             return null;
293         }
294
295         // parse whitespace
296 parseAndIgnoreWhitespace(source, pos);
297
298         // parse denominator
299 Number JavaDoc den = getDenominatorFormat().parse(source, pos);
300         if (den == null) {
301             // invalid integer number
302 // set index back to initial, error index should already be set
303 // character examined.
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 JavaDoc parseObject(String JavaDoc source, ParsePosition JavaDoc 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 JavaDoc format) {
329         if (format == null) {
330             throw new IllegalArgumentException JavaDoc(
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 JavaDoc format) {
343         if (format == null) {
344             throw new IllegalArgumentException JavaDoc(
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 JavaDoc source, ParsePosition JavaDoc 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 JavaDoc source, ParsePosition JavaDoc 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 }
389
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