001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    
018    package org.apache.commons.math.fraction;
019    
020    import java.text.FieldPosition;
021    import java.text.NumberFormat;
022    import java.text.ParseException;
023    import java.text.ParsePosition;
024    import java.util.Locale;
025    
026    import org.apache.commons.math.ConvergenceException;
027    import org.apache.commons.math.MathRuntimeException;
028    
029    /**
030     * Formats a Fraction number in proper format or improper format.  The number
031     * format for each of the whole number, numerator and, denominator can be
032     * configured.
033     *
034     * @since 1.1
035     * @version $Revision: 811685 $ $Date: 2009-09-05 13:36:48 -0400 (Sat, 05 Sep 2009) $
036     */
037    public class FractionFormat extends AbstractFormat {
038    
039        /** Serializable version identifier */
040        private static final long serialVersionUID = 3008655719530972611L;
041    
042        /**
043         * Create an improper formatting instance with the default number format
044         * for the numerator and denominator.
045         */
046        public FractionFormat() {
047        }
048    
049        /**
050         * Create an improper formatting instance with a custom number format for
051         * both the numerator and denominator.
052         * @param format the custom format for both the numerator and denominator.
053         */
054        public FractionFormat(final NumberFormat format) {
055            super(format);
056        }
057    
058        /**
059         * Create an improper formatting instance with a custom number format for
060         * the numerator and a custom number format for the denominator.
061         * @param numeratorFormat the custom format for the numerator.
062         * @param denominatorFormat the custom format for the denominator.
063         */
064        public FractionFormat(final NumberFormat numeratorFormat,
065                              final NumberFormat denominatorFormat) {
066            super(numeratorFormat, denominatorFormat);
067        }
068    
069        /**
070         * Get the set of locales for which complex formats are available.  This
071         * is the same set as the {@link NumberFormat} set.
072         * @return available complex format locales.
073         */
074        public static Locale[] getAvailableLocales() {
075            return NumberFormat.getAvailableLocales();
076        }
077    
078        /**
079         * This static method calls formatFraction() on a default instance of
080         * FractionFormat.
081         *
082         * @param f Fraction object to format
083         * @return A formatted fraction in proper form.
084         */
085        public static String formatFraction(Fraction f) {
086            return getImproperInstance().format(f);
087        }
088    
089        /**
090         * Returns the default complex format for the current locale.
091         * @return the default complex format.
092         */
093        public static FractionFormat getImproperInstance() {
094            return getImproperInstance(Locale.getDefault());
095        }
096    
097        /**
098         * Returns the default complex format for the given locale.
099         * @param locale the specific locale used by the format.
100         * @return the complex format specific to the given locale.
101         */
102        public static FractionFormat getImproperInstance(final Locale locale) {
103            return new FractionFormat(getDefaultNumberFormat(locale));
104        }
105    
106        /**
107         * Returns the default complex format for the current locale.
108         * @return the default complex format.
109         */
110        public static FractionFormat getProperInstance() {
111            return getProperInstance(Locale.getDefault());
112        }
113    
114        /**
115         * Returns the default complex format for the given locale.
116         * @param locale the specific locale used by the format.
117         * @return the complex format specific to the given locale.
118         */
119        public static FractionFormat getProperInstance(final Locale locale) {
120            return new ProperFractionFormat(getDefaultNumberFormat(locale));
121        }
122    
123        /**
124         * Create a default number format.  The default number format is based on
125         * {@link NumberFormat#getNumberInstance(java.util.Locale)} with the only
126         * customizing is the maximum number of fraction digits, which is set to 0.
127         * @return the default number format.
128         */
129        protected static NumberFormat getDefaultNumberFormat() {
130            return getDefaultNumberFormat(Locale.getDefault());
131        }
132    
133        /**
134         * Formats a {@link Fraction} object to produce a string.  The fraction is
135         * output in improper format.
136         *
137         * @param fraction the object to format.
138         * @param toAppendTo where the text is to be appended
139         * @param pos On input: an alignment field, if desired. On output: the
140         *            offsets of the alignment field
141         * @return the value passed in as toAppendTo.
142         */
143        public StringBuffer format(final Fraction fraction,
144                                   final StringBuffer toAppendTo, final FieldPosition pos) {
145    
146            pos.setBeginIndex(0);
147            pos.setEndIndex(0);
148    
149            getNumeratorFormat().format(fraction.getNumerator(), toAppendTo, pos);
150            toAppendTo.append(" / ");
151            getDenominatorFormat().format(fraction.getDenominator(), toAppendTo,
152                pos);
153    
154            return toAppendTo;
155        }
156    
157        /**
158         * Formats an object and appends the result to a StringBuffer. <code>obj</code> must be either a
159         * {@link Fraction} object or a {@link Number} object.  Any other type of
160         * object will result in an {@link IllegalArgumentException} being thrown.
161         *
162         * @param obj the object to format.
163         * @param toAppendTo where the text is to be appended
164         * @param pos On input: an alignment field, if desired. On output: the
165         *            offsets of the alignment field
166         * @return the value passed in as toAppendTo.
167         * @see java.text.Format#format(java.lang.Object, java.lang.StringBuffer, java.text.FieldPosition)
168         * @throws IllegalArgumentException is <code>obj</code> is not a valid type.
169         */
170        @Override
171        public StringBuffer format(final Object obj,
172                                   final StringBuffer toAppendTo, final FieldPosition pos) {
173            StringBuffer ret = null;
174    
175            if (obj instanceof Fraction) {
176                ret = format((Fraction) obj, toAppendTo, pos);
177            } else if (obj instanceof Number) {
178                try {
179                    ret = format(new Fraction(((Number) obj).doubleValue()),
180                                 toAppendTo, pos);
181                } catch (ConvergenceException ex) {
182                    throw MathRuntimeException.createIllegalArgumentException(
183                        "cannot convert given object to a fraction number: {0}",
184                        ex.getLocalizedMessage());
185                }
186            } else {
187                throw MathRuntimeException.createIllegalArgumentException(
188                    "cannot format given object as a fraction number");
189            }
190    
191            return ret;
192        }
193    
194        /**
195         * Parses a string to produce a {@link Fraction} object.
196         * @param source the string to parse
197         * @return the parsed {@link Fraction} object.
198         * @exception ParseException if the beginning of the specified string
199         *            cannot be parsed.
200         */
201        @Override
202        public Fraction parse(final String source) throws ParseException {
203            final ParsePosition parsePosition = new ParsePosition(0);
204            final Fraction result = parse(source, parsePosition);
205            if (parsePosition.getIndex() == 0) {
206                throw MathRuntimeException.createParseException(
207                        parsePosition.getErrorIndex(),
208                        "unparseable fraction number: \"{0}\"", source);
209            }
210            return result;
211        }
212    
213        /**
214         * Parses a string to produce a {@link Fraction} object.  This method
215         * expects the string to be formatted as an improper fraction.
216         * @param source the string to parse
217         * @param pos input/ouput parsing parameter.
218         * @return the parsed {@link Fraction} object.
219         */
220        @Override
221        public Fraction parse(final String source, final ParsePosition pos) {
222            final int initialIndex = pos.getIndex();
223    
224            // parse whitespace
225            parseAndIgnoreWhitespace(source, pos);
226    
227            // parse numerator
228            final Number num = getNumeratorFormat().parse(source, pos);
229            if (num == null) {
230                // invalid integer number
231                // set index back to initial, error index should already be set
232                // character examined.
233                pos.setIndex(initialIndex);
234                return null;
235            }
236    
237            // parse '/'
238            final int startIndex = pos.getIndex();
239            final char c = parseNextCharacter(source, pos);
240            switch (c) {
241            case 0 :
242                // no '/'
243                // return num as a fraction
244                return new Fraction(num.intValue(), 1);
245            case '/' :
246                // found '/', continue parsing denominator
247                break;
248            default :
249                // invalid '/'
250                // set index back to initial, error index should be the last
251                // character examined.
252                pos.setIndex(initialIndex);
253                pos.setErrorIndex(startIndex);
254                return null;
255            }
256    
257            // parse whitespace
258            parseAndIgnoreWhitespace(source, pos);
259    
260            // parse denominator
261            final Number den = getDenominatorFormat().parse(source, pos);
262            if (den == null) {
263                // invalid integer number
264                // set index back to initial, error index should already be set
265                // character examined.
266                pos.setIndex(initialIndex);
267                return null;
268            }
269    
270            return new Fraction(num.intValue(), den.intValue());
271        }
272    
273    }