1/* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17package org.apache.commons.math.fraction; 18 19import java.text.FieldPosition; 20import java.text.NumberFormat; 21import java.text.ParsePosition; 22 23import org.apache.commons.math.exception.util.LocalizedFormats; 24import org.apache.commons.math.exception.NullArgumentException; 25import org.apache.commons.math.util.MathUtils; 26 27/** 28 * Formats a Fraction number in proper format. The number format for each of 29 * the whole number, numerator and, denominator can be configured. 30 * <p> 31 * Minus signs are only allowed in the whole number part - i.e., 32 * "-3 1/2" is legitimate and denotes -7/2, but "-3 -1/2" is invalid and 33 * will result in a <code>ParseException</code>.</p> 34 * 35 * @since 1.1 36 * @version $Revision: 983921 $ $Date: 2010-08-10 12:46:06 +0200 (mar. 10 août 2010) $ 37 */ 38public class ProperFractionFormat extends FractionFormat { 39 40 /** Serializable version identifier */ 41 private static final long serialVersionUID = 760934726031766749L; 42 43 /** The format used for the whole number. */ 44 private NumberFormat wholeFormat; 45 46 /** 47 * Create a proper formatting instance with the default number format for 48 * the whole, numerator, and denominator. 49 */ 50 public ProperFractionFormat() { 51 this(getDefaultNumberFormat()); 52 } 53 54 /** 55 * Create a proper formatting instance with a custom number format for the 56 * whole, numerator, and denominator. 57 * @param format the custom format for the whole, numerator, and 58 * denominator. 59 */ 60 public ProperFractionFormat(NumberFormat format) { 61 this(format, (NumberFormat)format.clone(), (NumberFormat)format.clone()); 62 } 63 64 /** 65 * Create a proper formatting instance with a custom number format for each 66 * of the whole, numerator, and denominator. 67 * @param wholeFormat the custom format for the whole. 68 * @param numeratorFormat the custom format for the numerator. 69 * @param denominatorFormat the custom format for the denominator. 70 */ 71 public ProperFractionFormat(NumberFormat wholeFormat, 72 NumberFormat numeratorFormat, 73 NumberFormat denominatorFormat) 74 { 75 super(numeratorFormat, denominatorFormat); 76 setWholeFormat(wholeFormat); 77 } 78 79 /** 80 * Formats a {@link Fraction} object to produce a string. The fraction 81 * is output in proper format. 82 * 83 * @param fraction the object to format. 84 * @param toAppendTo where the text is to be appended 85 * @param pos On input: an alignment field, if desired. On output: the 86 * offsets of the alignment field 87 * @return the value passed in as toAppendTo. 88 */ 89 @Override 90 public StringBuffer format(Fraction fraction, StringBuffer toAppendTo, 91 FieldPosition pos) { 92 93 pos.setBeginIndex(0); 94 pos.setEndIndex(0); 95 96 int num = fraction.getNumerator(); 97 int den = fraction.getDenominator(); 98 int whole = num / den; 99 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} 233