    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    import org.apache.commons.math.exception.util.LocalizedFormats;
    029
    030    /**
    031     * Formats a Fraction number in proper format or improper format.  The number
    032     * format for each of the whole number, numerator and, denominator can be
    033     * configured.
    034     *
    035     * @since 1.1
    036     * @version $Revision: 983921 $ $Date: 2010-08-10 12:46:06 +0200 (mar. 10 ao??t 2010) $
    037     */
    038    public class FractionFormat extends AbstractFormat {
    039
    040        /** Serializable version identifier */
    041        private static final long serialVersionUID = 3008655719530972611L;
    042
    043        /**
    044         * Create an improper formatting instance with the default number format
    045         * for the numerator and denominator.
    046         */
    047        public FractionFormat() {
    048        }
    049
    050        /**
    051         * Create an improper formatting instance with a custom number format for
    052         * both the numerator and denominator.
    053         * @param format the custom format for both the numerator and denominator.
    054         */
    055        public FractionFormat(final NumberFormat format) {
    056            super(format);
    057        }
    058
    059        /**
    060         * Create an improper formatting instance with a custom number format for
    061         * the numerator and a custom number format for the denominator.
    062         * @param numeratorFormat the custom format for the numerator.
    063         * @param denominatorFormat the custom format for the denominator.
    064         */
    065        public FractionFormat(final NumberFormat numeratorFormat,
    066                              final NumberFormat denominatorFormat) {
    067            super(numeratorFormat, denominatorFormat);
    068        }
    069
    070        /**
    071         * Get the set of locales for which complex formats are available.  This
    072         * is the same set as the {@link NumberFormat} set.
    073         * @return available complex format locales.
    074         */
    075        public static Locale[] getAvailableLocales() {
    076            return NumberFormat.getAvailableLocales();
    077        }
    078
    079        /**
    080         * This static method calls formatFraction() on a default instance of
    081         * FractionFormat.
    082         *
    083         * @param f Fraction object to format
    084         * @return A formatted fraction in proper form.
    085         */
    086        public static String formatFraction(Fraction f) {
    087            return getImproperInstance().format(f);
    088        }
    089
    090        /**
    091         * Returns the default complex format for the current locale.
    092         * @return the default complex format.
    093         */
    094        public static FractionFormat getImproperInstance() {
    095            return getImproperInstance(Locale.getDefault());
    096        }
    097
    098        /**
    099         * Returns the default complex format for the given locale.
    100         * @param locale the specific locale used by the format.
    101         * @return the complex format specific to the given locale.
    102         */
    103        public static FractionFormat getImproperInstance(final Locale locale) {
    104            return new FractionFormat(getDefaultNumberFormat(locale));
    105        }
    106
    107        /**
    108         * Returns the default complex format for the current locale.
    109         * @return the default complex format.
    110         */
    111        public static FractionFormat getProperInstance() {
    112            return getProperInstance(Locale.getDefault());
    113        }
    114
    115        /**
    116         * Returns the default complex format for the given locale.
    117         * @param locale the specific locale used by the format.
    118         * @return the complex format specific to the given locale.
    119         */
    120        public static FractionFormat getProperInstance(final Locale locale) {
    121            return new ProperFractionFormat(getDefaultNumberFormat(locale));
    122        }
    123
    124        /**
    125         * Create a default number format.  The default number format is based on
    126         * {@link NumberFormat#getNumberInstance(java.util.Locale)} with the only
    127         * customizing is the maximum number of fraction digits, which is set to 0.
    128         * @return the default number format.
    129         */
    130        protected static NumberFormat getDefaultNumberFormat() {
    131            return getDefaultNumberFormat(Locale.getDefault());
    132        }
    133
    134        /**
    135         * Formats a {@link Fraction} object to produce a string.  The fraction is
    136         * output in improper format.
    137         *
    138         * @param fraction the object to format.
    139         * @param toAppendTo where the text is to be appended
    140         * @param pos On input: an alignment field, if desired. On output: the
    141         *            offsets of the alignment field
    142         * @return the value passed in as toAppendTo.
    143         */
    144        public StringBuffer format(final Fraction fraction,
    145                                   final StringBuffer toAppendTo, final FieldPosition pos) {
    146
    147            pos.setBeginIndex(0);
    148            pos.setEndIndex(0);
    149
    150            getNumeratorFormat().format(fraction.getNumerator(), toAppendTo, pos);
    151            toAppendTo.append(" / ");
    152            getDenominatorFormat().format(fraction.getDenominator(), toAppendTo,
    153                pos);
    154
    155            return toAppendTo;
    156        }
    157
    158        /**
    159         * Formats an object and appends the result to a StringBuffer. <code>obj</code> must be either a
    160         * {@link Fraction} object or a {@link Number} object.  Any other type of
    161         * object will result in an {@link IllegalArgumentException} being thrown.
    162         *
    163         * @param obj 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         * @see java.text.Format#format(java.lang.Object, java.lang.StringBuffer, java.text.FieldPosition)
    169         * @throws IllegalArgumentException is <code>obj</code> is not a valid type.
    170         */
    171        @Override
    172        public StringBuffer format(final Object obj,
    173                                   final StringBuffer toAppendTo, final FieldPosition pos) {
    174            StringBuffer ret = null;
    175
    176            if (obj instanceof Fraction) {
    177                ret = format((Fraction) obj, toAppendTo, pos);
    178            } else if (obj instanceof Number) {
    179                try {
    180                    ret = format(new Fraction(((Number) obj).doubleValue()),
    181                                 toAppendTo, pos);
    182                } catch (ConvergenceException ex) {
    183                    throw MathRuntimeException.createIllegalArgumentException(
    184                        LocalizedFormats.CANNOT_CONVERT_OBJECT_TO_FRACTION,
    185                        ex.getLocalizedMessage());
    186                }
    187            } else {
    188                throw MathRuntimeException.createIllegalArgumentException(
    189                    LocalizedFormats.CANNOT_FORMAT_OBJECT_TO_FRACTION);
    190            }
    191
    192            return ret;
    193        }
    194
    195        /**
    196         * Parses a string to produce a {@link Fraction} object.
    197         * @param source the string to parse
    198         * @return the parsed {@link Fraction} object.
    199         * @exception ParseException if the beginning of the specified string
    200         *            cannot be parsed.
    201         */
    202        @Override
    203        public Fraction parse(final String source) throws ParseException {
    204            final ParsePosition parsePosition = new ParsePosition(0);
    205            final Fraction result = parse(source, parsePosition);
    206            if (parsePosition.getIndex() == 0) {
    207                throw MathRuntimeException.createParseException(
    208                        parsePosition.getErrorIndex(),
    209                        LocalizedFormats.UNPARSEABLE_FRACTION_NUMBER, source);
    210            }
    211            return result;
    212        }
    213
    214        /**
    215         * Parses a string to produce a {@link Fraction} object.  This method
    216         * expects the string to be formatted as an improper fraction.
    217         * @param source the string to parse
    218         * @param pos input/ouput parsing parameter.
    219         * @return the parsed {@link Fraction} object.
    220         */
    221        @Override
    222        public Fraction parse(final String source, final ParsePosition pos) {
    223            final int initialIndex = pos.getIndex();
    224
    225            // parse whitespace
    226            parseAndIgnoreWhitespace(source, pos);
    227
    228            // parse numerator
    229            final Number num = getNumeratorFormat().parse(source, pos);
    230            if (num == null) {
    231                // invalid integer number
    232                // set index back to initial, error index should already be set
    233                // character examined.
    234                pos.setIndex(initialIndex);
    235                return null;
    236            }
    237
    238            // parse '/'
    239            final int startIndex = pos.getIndex();
    240            final char c = parseNextCharacter(source, pos);
    241            switch (c) {
    242            case 0 :
    243                // no '/'
    244                // return num as a fraction
    245                return new Fraction(num.intValue(), 1);
    246            case '/' :
    247                // found '/', continue parsing denominator
    248                break;
    249            default :
    250                // invalid '/'
    251                // set index back to initial, error index should be the last
    252                // character examined.
    253                pos.setIndex(initialIndex);
    254                pos.setErrorIndex(startIndex);
    255                return null;
    256            }
    257
    258            // parse whitespace
    259            parseAndIgnoreWhitespace(source, pos);
    260
    261            // parse denominator
    262            final Number den = getDenominatorFormat().parse(source, pos);
    263            if (den == null) {
    264                // invalid integer number
    265                // set index back to initial, error index should already be set
    266                // character examined.
    267                pos.setIndex(initialIndex);
    268                return null;
    269            }
    270
    271            return new Fraction(num.intValue(), den.intValue());
    272        }
    273
    274    }