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 }