    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.math3.fraction;
    019
    020    import java.text.FieldPosition;
    021    import java.text.NumberFormat;
    022    import java.text.ParsePosition;
    023    import java.util.Locale;
    024
    025    import org.apache.commons.math3.exception.MathIllegalArgumentException;
    026    import org.apache.commons.math3.exception.MathParseException;
    027    import org.apache.commons.math3.exception.util.LocalizedFormats;
    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 $Id: FractionFormat.java 1416643 2012-12-03 19:37:14Z tn $
    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 FractionConversionException if the number cannot be converted to a fraction
    169         * @throws MathIllegalArgumentException if <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            throws FractionConversionException, MathIllegalArgumentException {
    175            StringBuffer ret = null;
    176
    177            if (obj instanceof Fraction) {
    178                ret = format((Fraction) obj, toAppendTo, pos);
    179            } else if (obj instanceof Number) {
    180                ret = format(new Fraction(((Number) obj).doubleValue()), toAppendTo, pos);
    181            } else {
    182                throw new MathIllegalArgumentException(LocalizedFormats.CANNOT_FORMAT_OBJECT_TO_FRACTION);
    183            }
    184
    185            return ret;
    186        }
    187
    188        /**
    189         * Parses a string to produce a {@link Fraction} object.
    190         * @param source the string to parse
    191         * @return the parsed {@link Fraction} object.
    192         * @exception MathParseException if the beginning of the specified string
    193         *            cannot be parsed.
    194         */
    195        @Override
    196        public Fraction parse(final String source) throws MathParseException {
    197            final ParsePosition parsePosition = new ParsePosition(0);
    198            final Fraction result = parse(source, parsePosition);
    199            if (parsePosition.getIndex() == 0) {
    200                throw new MathParseException(source, parsePosition.getErrorIndex(), Fraction.class);
    201            }
    202            return result;
    203        }
    204
    205        /**
    206         * Parses a string to produce a {@link Fraction} object.  This method
    207         * expects the string to be formatted as an improper fraction.
    208         * @param source the string to parse
    209         * @param pos input/output parsing parameter.
    210         * @return the parsed {@link Fraction} object.
    211         */
    212        @Override
    213        public Fraction parse(final String source, final ParsePosition pos) {
    214            final int initialIndex = pos.getIndex();
    215
    216            // parse whitespace
    217            parseAndIgnoreWhitespace(source, pos);
    218
    219            // parse numerator
    220            final Number num = getNumeratorFormat().parse(source, pos);
    221            if (num == null) {
    222                // invalid integer number
    223                // set index back to initial, error index should already be set
    224                // character examined.
    225                pos.setIndex(initialIndex);
    226                return null;
    227            }
    228
    229            // parse '/'
    230            final int startIndex = pos.getIndex();
    231            final char c = parseNextCharacter(source, pos);
    232            switch (c) {
    233            case 0 :
    234                // no '/'
    235                // return num as a fraction
    236                return new Fraction(num.intValue(), 1);
    237            case '/' :
    238                // found '/', continue parsing denominator
    239                break;
    240            default :
    241                // invalid '/'
    242                // set index back to initial, error index should be the last
    243                // character examined.
    244                pos.setIndex(initialIndex);
    245                pos.setErrorIndex(startIndex);
    246                return null;
    247            }
    248
    249            // parse whitespace
    250            parseAndIgnoreWhitespace(source, pos);
    251
    252            // parse denominator
    253            final Number den = getDenominatorFormat().parse(source, pos);
    254            if (den == null) {
    255                // invalid integer number
    256                // set index back to initial, error index should already be set
    257                // character examined.
    258                pos.setIndex(initialIndex);
    259                return null;
    260            }
    261
    262            return new Fraction(num.intValue(), den.intValue());
    263        }
    264
    265    }