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 }