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.math3.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.math3.exception.util.LocalizedFormats;
025    import org.apache.commons.math3.exception.NullArgumentException;
026    
027    /**
028     * Formats a BigFraction 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 $Id: ProperBigFractionFormat.java 1416643 2012-12-03 19:37:14Z tn $
037     */
038    public class ProperBigFractionFormat extends BigFractionFormat {
039    
040        /** Serializable version identifier */
041        private static final long serialVersionUID = -6337346779577272307L;
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 ProperBigFractionFormat() {
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 ProperBigFractionFormat(final 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 ProperBigFractionFormat(final NumberFormat wholeFormat,
072                                       final NumberFormat numeratorFormat,
073                                       final NumberFormat denominatorFormat) {
074            super(numeratorFormat, denominatorFormat);
075            setWholeFormat(wholeFormat);
076        }
077    
078        /**
079         * Formats a {@link BigFraction} object to produce a string.  The BigFraction
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(final BigFraction fraction,
090                                   final StringBuffer toAppendTo, final FieldPosition pos) {
091    
092            pos.setBeginIndex(0);
093            pos.setEndIndex(0);
094    
095            BigInteger num = fraction.getNumerator();
096            BigInteger den = fraction.getDenominator();
097            BigInteger whole = num.divide(den);
098            num = num.remainder(den);
099    
100            if (!BigInteger.ZERO.equals(whole)) {
101                getWholeFormat().format(whole, toAppendTo, pos);
102                toAppendTo.append(' ');
103                if (num.compareTo(BigInteger.ZERO) < 0) {
104                    num = num.negate();
105                }
106            }
107            getNumeratorFormat().format(num, toAppendTo, pos);
108            toAppendTo.append(" / ");
109            getDenominatorFormat().format(den, toAppendTo, 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 BigFraction} object.  This method
124         * expects the string to be formatted as a proper BigFraction.
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 BigFraction} object.
133         */
134        @Override
135        public BigFraction parse(final String source, final ParsePosition pos) {
136            // try to parse improper BigFraction
137            BigFraction ret = super.parse(source, pos);
138            if (ret != null) {
139                return ret;
140            }
141    
142            final int initialIndex = pos.getIndex();
143    
144            // parse whitespace
145            parseAndIgnoreWhitespace(source, pos);
146    
147            // parse whole
148            BigInteger whole = parseNextBigInteger(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            BigInteger num = parseNextBigInteger(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.compareTo(BigInteger.ZERO) < 0) {
171                // minus signs should be leading, invalid expression
172                pos.setIndex(initialIndex);
173                return null;
174            }
175    
176            // parse '/'
177            final int startIndex = pos.getIndex();
178            final char c = parseNextCharacter(source, pos);
179            switch (c) {
180            case 0 :
181                // no '/'
182                // return num as a BigFraction
183                return new BigFraction(num);
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            final BigInteger den = parseNextBigInteger(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.compareTo(BigInteger.ZERO) < 0) {
210                // minus signs must be leading, invalid
211                pos.setIndex(initialIndex);
212                return null;
213            }
214    
215            boolean wholeIsNeg = whole.compareTo(BigInteger.ZERO) < 0;
216            if (wholeIsNeg) {
217                whole = whole.negate();
218            }
219            num = whole.multiply(den).add(num);
220            if (wholeIsNeg) {
221                num = num.negate();
222            }
223    
224            return new BigFraction(num, den);
225    
226        }
227    
228        /**
229         * Modify the whole format.
230         * @param format The new whole format value.
231         * @throws NullArgumentException if {@code format} is {@code null}.
232         */
233        public void setWholeFormat(final NumberFormat format) {
234            if (format == null) {
235                throw new NullArgumentException(LocalizedFormats.WHOLE_FORMAT);
236            }
237            this.wholeFormat = format;
238        }
239    }