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    package org.apache.commons.math.fraction;
018    
019    import java.text.FieldPosition;
020    import java.text.NumberFormat;
021    import java.text.ParsePosition;
022    
023    import org.apache.commons.math.MathRuntimeException;
024    import org.apache.commons.math.util.MathUtils;
025    
026    /**
027     * Formats a Fraction number in proper format.  The number format for each of
028     * the whole number, numerator and, denominator can be configured.
029     * <p>
030     * Minus signs are only allowed in the whole number part - i.e.,
031     * "-3 1/2" is legitimate and denotes -7/2, but "-3 -1/2" is invalid and
032     * will result in a <code>ParseException</code>.</p>
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 ProperFractionFormat extends FractionFormat {
038    
039        /** Serializable version identifier */
040        private static final long serialVersionUID = 760934726031766749L;
041    
042        /** The format used for the whole number. */
043        private NumberFormat wholeFormat;
044    
045        /**
046         * Create a proper formatting instance with the default number format for
047         * the whole, numerator, and denominator.
048         */
049        public ProperFractionFormat() {
050            this(getDefaultNumberFormat());
051        }
052    
053        /**
054         * Create a proper formatting instance with a custom number format for the
055         * whole, numerator, and denominator.
056         * @param format the custom format for the whole, numerator, and
057         *        denominator.
058         */
059        public ProperFractionFormat(NumberFormat format) {
060            this(format, (NumberFormat)format.clone(), (NumberFormat)format.clone());
061        }
062    
063        /**
064         * Create a proper formatting instance with a custom number format for each
065         * of the whole, numerator, and denominator.
066         * @param wholeFormat the custom format for the whole.
067         * @param numeratorFormat the custom format for the numerator.
068         * @param denominatorFormat the custom format for the denominator.
069         */
070        public ProperFractionFormat(NumberFormat wholeFormat,
071                NumberFormat numeratorFormat,
072                NumberFormat denominatorFormat)
073        {
074            super(numeratorFormat, denominatorFormat);
075            setWholeFormat(wholeFormat);
076        }
077    
078        /**
079         * Formats a {@link Fraction} object to produce a string.  The fraction
080         * is output in proper format.
081         *
082         * @param fraction the object to format.
083         * @param toAppendTo where the text is to be appended
084         * @param pos On input: an alignment field, if desired. On output: the
085         *            offsets of the alignment field
086         * @return the value passed in as toAppendTo.
087         */
088        @Override
089        public StringBuffer format(Fraction fraction, StringBuffer toAppendTo,
090                FieldPosition pos) {
091    
092            pos.setBeginIndex(0);
093            pos.setEndIndex(0);
094    
095            int num = fraction.getNumerator();
096            int den = fraction.getDenominator();
097            int whole = num / den;
098            num = num % den;
099    
100            if (whole != 0) {
101                getWholeFormat().format(whole, toAppendTo, pos);
102                toAppendTo.append(' ');
103                num = Math.abs(num);
104            }
105            getNumeratorFormat().format(num, toAppendTo, pos);
106            toAppendTo.append(" / ");
107            getDenominatorFormat().format(den, toAppendTo,
108                pos);
109    
110            return toAppendTo;
111        }
112    
113        /**
114         * Access the whole format.
115         * @return the whole format.
116         */
117        public NumberFormat getWholeFormat() {
118            return wholeFormat;
119        }
120    
121        /**
122         * Parses a string to produce a {@link Fraction} object.  This method
123         * expects the string to be formatted as a proper fraction.
124         * <p>
125         * Minus signs are only allowed in the whole number part - i.e.,
126         * "-3 1/2" is legitimate and denotes -7/2, but "-3 -1/2" is invalid and
127         * will result in a <code>ParseException</code>.</p>
128         *
129         * @param source the string to parse
130         * @param pos input/ouput parsing parameter.
131         * @return the parsed {@link Fraction} object.
132         */
133        @Override
134        public Fraction parse(String source, ParsePosition pos) {
135            // try to parse improper fraction
136            Fraction ret = super.parse(source, pos);
137            if (ret != null) {
138                return ret;
139            }
140    
141            int initialIndex = pos.getIndex();
142    
143            // parse whitespace
144            parseAndIgnoreWhitespace(source, pos);
145    
146            // parse whole
147            Number whole = getWholeFormat().parse(source, pos);
148            if (whole == null) {
149                // invalid integer number
150                // set index back to initial, error index should already be set
151                // character examined.
152                pos.setIndex(initialIndex);
153                return null;
154            }
155    
156            // parse whitespace
157            parseAndIgnoreWhitespace(source, pos);
158    
159            // parse numerator
160            Number num = getNumeratorFormat().parse(source, pos);
161            if (num == null) {
162                // invalid integer number
163                // set index back to initial, error index should already be set
164                // character examined.
165                pos.setIndex(initialIndex);
166                return null;
167            }
168    
169            if (num.intValue() < 0) {
170                // minus signs should be leading, invalid expression
171                pos.setIndex(initialIndex);
172                return null;
173            }
174    
175            // parse '/'
176            int startIndex = pos.getIndex();
177            char c = parseNextCharacter(source, pos);
178            switch (c) {
179            case 0 :
180                // no '/'
181                // return num as a fraction
182                return new Fraction(num.intValue(), 1);
183            case '/' :
184                // found '/', continue parsing denominator
185                break;
186            default :
187                // invalid '/'
188                // set index back to initial, error index should be the last
189                // character examined.
190                pos.setIndex(initialIndex);
191                pos.setErrorIndex(startIndex);
192                return null;
193            }
194    
195            // parse whitespace
196            parseAndIgnoreWhitespace(source, pos);
197    
198            // parse denominator
199            Number den = getDenominatorFormat().parse(source, pos);
200            if (den == null) {
201                // invalid integer number
202                // set index back to initial, error index should already be set
203                // character examined.
204                pos.setIndex(initialIndex);
205                return null;
206            }
207    
208            if (den.intValue() < 0) {
209                // minus signs must be leading, invalid
210                pos.setIndex(initialIndex);
211                return null;
212            }
213    
214            int w = whole.intValue();
215            int n = num.intValue();
216            int d = den.intValue();
217            return new Fraction(((Math.abs(w) * d) + n) * MathUtils.sign(w), d);
218        }
219    
220        /**
221         * Modify the whole format.
222         * @param format The new whole format value.
223         * @throws IllegalArgumentException if <code>format</code> is
224         *         <code>null</code>.
225         */
226        public void setWholeFormat(NumberFormat format) {
227            if (format == null) {
228                throw MathRuntimeException.createIllegalArgumentException(
229                    "whole format can not be null");
230            }
231            this.wholeFormat = format;
232        }
233    }