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
018package org.apache.commons.math3.fraction;
019
020import java.text.FieldPosition;
021import java.text.NumberFormat;
022import java.text.ParsePosition;
023import java.util.Locale;
024
025import org.apache.commons.math3.exception.MathIllegalArgumentException;
026import org.apache.commons.math3.exception.MathParseException;
027import 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 */
037public 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}