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.math.BigInteger;
020    import java.text.FieldPosition;
021    import java.text.NumberFormat;
022    import java.text.ParsePosition;
023    
024    import org.apache.commons.math.MathRuntimeException;
025    
026    /**
027     * Formats a BigFraction 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: 762087 $ $Date: 2009-04-05 10:20:18 -0400 (Sun, 05 Apr 2009) $
036     */
037    public class ProperBigFractionFormat extends BigFractionFormat {
038        
039        /** Serializable version identifier */
040        private static final long serialVersionUID = -6337346779577272307L;
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 ProperBigFractionFormat() {
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 ProperBigFractionFormat(final 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 ProperBigFractionFormat(final NumberFormat wholeFormat,
071                                       final NumberFormat numeratorFormat,
072                                       final NumberFormat denominatorFormat) {
073            super(numeratorFormat, denominatorFormat);
074            setWholeFormat(wholeFormat);
075        }
076        
077        /**
078         * Formats a {@link BigFraction} object to produce a string.  The BigFraction
079         * is output in proper format.
080         *
081         * @param fraction the object to format.
082         * @param toAppendTo where the text is to be appended
083         * @param pos On input: an alignment field, if desired. On output: the
084         *            offsets of the alignment field
085         * @return the value passed in as toAppendTo.
086         */
087        @Override
088        public StringBuffer format(final BigFraction fraction,
089                                   final StringBuffer toAppendTo, final FieldPosition pos) {
090            
091            pos.setBeginIndex(0);
092            pos.setEndIndex(0);
093    
094            BigInteger num = fraction.getNumerator();
095            BigInteger den = fraction.getDenominator();
096            BigInteger whole = num.divide(den);
097            num = num.remainder(den);
098            
099            if (!BigInteger.ZERO.equals(whole)) {
100                getWholeFormat().format(whole, toAppendTo, pos);
101                toAppendTo.append(' ');
102                if (num.compareTo(BigInteger.ZERO) < 0) {
103                    num = num.negate();
104                }
105            }
106            getNumeratorFormat().format(num, toAppendTo, pos);
107            toAppendTo.append(" / ");
108            getDenominatorFormat().format(den, toAppendTo, 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 BigFraction} object.  This method
123         * expects the string to be formatted as a proper BigFraction.
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 BigFraction} object.
132         */
133        @Override
134        public BigFraction parse(final String source, final ParsePosition pos) {
135            // try to parse improper BigFraction
136            BigFraction ret = super.parse(source, pos);
137            if (ret != null) {
138                return ret;
139            }
140            
141            final int initialIndex = pos.getIndex();
142    
143            // parse whitespace
144            parseAndIgnoreWhitespace(source, pos);
145    
146            // parse whole
147            BigInteger whole = parseNextBigInteger(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            BigInteger num = parseNextBigInteger(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.compareTo(BigInteger.ZERO) < 0) {
170                // minus signs should be leading, invalid expression
171                pos.setIndex(initialIndex);
172                return null;
173            }
174    
175            // parse '/'
176            final int startIndex = pos.getIndex();
177            final char c = parseNextCharacter(source, pos);
178            switch (c) {
179            case 0 :
180                // no '/'
181                // return num as a BigFraction
182                return new BigFraction(num);
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            final BigInteger den = parseNextBigInteger(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.compareTo(BigInteger.ZERO) < 0) {
209                // minus signs must be leading, invalid
210                pos.setIndex(initialIndex);
211                return null;
212            }
213    
214            boolean wholeIsNeg = whole.compareTo(BigInteger.ZERO) < 0;
215            if (wholeIsNeg) {
216                whole = whole.negate();
217            }
218            num = whole.multiply(den).add(num);
219            if (wholeIsNeg) {
220                num = num.negate();
221            }
222    
223            return new BigFraction(num, den);
224    
225        }
226        
227        /**
228         * Modify the whole format.
229         * @param format The new whole format value.
230         * @throws IllegalArgumentException if <code>format</code> is
231         *         <code>null</code>.
232         */
233        public void setWholeFormat(final NumberFormat format) {
234            if (format == null) {
235                throw MathRuntimeException.createIllegalArgumentException(
236                    "whole format can not be null");
237            }
238            this.wholeFormat = format;
239        }
240    
241    }