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.exception.util.LocalizedFormats;
024    import org.apache.commons.math.exception.NullArgumentException;
025    import org.apache.commons.math.util.MathUtils;
026    
027    /**
028     * Formats a Fraction number in proper format.  The number format for each of
029     * the whole number, numerator and, denominator can be configured.
030     * <p>
031     * Minus signs are only allowed in the whole number part - i.e.,
032     * "-3 1/2" is legitimate and denotes -7/2, but "-3 -1/2" is invalid and
033     * will result in a <code>ParseException</code>.</p>
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 ProperFractionFormat extends FractionFormat {
039    
040        /** Serializable version identifier */
041        private static final long serialVersionUID = 760934726031766749L;
042    
043        /** The format used for the whole number. */
044        private NumberFormat wholeFormat;
045    
046        /**
047         * Create a proper formatting instance with the default number format for
048         * the whole, numerator, and denominator.
049         */
050        public ProperFractionFormat() {
051            this(getDefaultNumberFormat());
052        }
053    
054        /**
055         * Create a proper formatting instance with a custom number format for the
056         * whole, numerator, and denominator.
057         * @param format the custom format for the whole, numerator, and
058         *        denominator.
059         */
060        public ProperFractionFormat(NumberFormat format) {
061            this(format, (NumberFormat)format.clone(), (NumberFormat)format.clone());
062        }
063    
064        /**
065         * Create a proper formatting instance with a custom number format for each
066         * of the whole, numerator, and denominator.
067         * @param wholeFormat the custom format for the whole.
068         * @param numeratorFormat the custom format for the numerator.
069         * @param denominatorFormat the custom format for the denominator.
070         */
071        public ProperFractionFormat(NumberFormat wholeFormat,
072                NumberFormat numeratorFormat,
073                NumberFormat denominatorFormat)
074        {
075            super(numeratorFormat, denominatorFormat);
076            setWholeFormat(wholeFormat);
077        }
078    
079        /**
080         * Formats a {@link Fraction} object to produce a string.  The fraction
081         * is output in proper format.
082         *
083         * @param fraction the object to format.
084         * @param toAppendTo where the text is to be appended
085         * @param pos On input: an alignment field, if desired. On output: the
086         *            offsets of the alignment field
087         * @return the value passed in as toAppendTo.
088         */
089        @Override
090        public StringBuffer format(Fraction fraction, StringBuffer toAppendTo,
091                FieldPosition pos) {
092    
093            pos.setBeginIndex(0);
094            pos.setEndIndex(0);
095    
096            int num = fraction.getNumerator();
097            int den = fraction.getDenominator();
098            int whole = num / den;
099            num = num % den;
100    
101            if (whole != 0) {
102                getWholeFormat().format(whole, toAppendTo, pos);
103                toAppendTo.append(' ');
104                num = Math.abs(num);
105            }
106            getNumeratorFormat().format(num, toAppendTo, pos);
107            toAppendTo.append(" / ");
108            getDenominatorFormat().format(den, toAppendTo,
109                pos);
110    
111            return toAppendTo;
112        }
113    
114        /**
115         * Access the whole format.
116         * @return the whole format.
117         */
118        public NumberFormat getWholeFormat() {
119            return wholeFormat;
120        }
121    
122        /**
123         * Parses a string to produce a {@link Fraction} object.  This method
124         * expects the string to be formatted as a proper fraction.
125         * <p>
126         * Minus signs are only allowed in the whole number part - i.e.,
127         * "-3 1/2" is legitimate and denotes -7/2, but "-3 -1/2" is invalid and
128         * will result in a <code>ParseException</code>.</p>
129         *
130         * @param source the string to parse
131         * @param pos input/ouput parsing parameter.
132         * @return the parsed {@link Fraction} object.
133         */
134        @Override
135        public Fraction parse(String source, ParsePosition pos) {
136            // try to parse improper fraction
137            Fraction ret = super.parse(source, pos);
138            if (ret != null) {
139                return ret;
140            }
141    
142            int initialIndex = pos.getIndex();
143    
144            // parse whitespace
145            parseAndIgnoreWhitespace(source, pos);
146    
147            // parse whole
148            Number whole = getWholeFormat().parse(source, pos);
149            if (whole == null) {
150                // invalid integer number
151                // set index back to initial, error index should already be set
152                // character examined.
153                pos.setIndex(initialIndex);
154                return null;
155            }
156    
157            // parse whitespace
158            parseAndIgnoreWhitespace(source, pos);
159    
160            // parse numerator
161            Number num = getNumeratorFormat().parse(source, pos);
162            if (num == null) {
163                // invalid integer number
164                // set index back to initial, error index should already be set
165                // character examined.
166                pos.setIndex(initialIndex);
167                return null;
168            }
169    
170            if (num.intValue() < 0) {
171                // minus signs should be leading, invalid expression
172                pos.setIndex(initialIndex);
173                return null;
174            }
175    
176            // parse '/'
177            int startIndex = pos.getIndex();
178            char c = parseNextCharacter(source, pos);
179            switch (c) {
180            case 0 :
181                // no '/'
182                // return num as a fraction
183                return new Fraction(num.intValue(), 1);
184            case '/' :
185                // found '/', continue parsing denominator
186                break;
187            default :
188                // invalid '/'
189                // set index back to initial, error index should be the last
190                // character examined.
191                pos.setIndex(initialIndex);
192                pos.setErrorIndex(startIndex);
193                return null;
194            }
195    
196            // parse whitespace
197            parseAndIgnoreWhitespace(source, pos);
198    
199            // parse denominator
200            Number den = getDenominatorFormat().parse(source, pos);
201            if (den == null) {
202                // invalid integer number
203                // set index back to initial, error index should already be set
204                // character examined.
205                pos.setIndex(initialIndex);
206                return null;
207            }
208    
209            if (den.intValue() < 0) {
210                // minus signs must be leading, invalid
211                pos.setIndex(initialIndex);
212                return null;
213            }
214    
215            int w = whole.intValue();
216            int n = num.intValue();
217            int d = den.intValue();
218            return new Fraction(((Math.abs(w) * d) + n) * MathUtils.sign(w), d);
219        }
220    
221        /**
222         * Modify the whole format.
223         * @param format The new whole format value.
224         * @throws NullArgumentException if {@code format} is {@code null}.
225         */
226        public void setWholeFormat(NumberFormat format) {
227            if (format == null) {
228                throw new NullArgumentException(LocalizedFormats.WHOLE_FORMAT);
229            }
230            this.wholeFormat = format;
231        }
232    }