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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;
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         // parse whitespace
263         parseAndIgnoreWhitespace(source, pos);
264 
265         // parse numerator
266         Number 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 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 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 }