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 */ 17 package org.apache.commons.math.fraction; 18 19 import java.text.FieldPosition; 20 import java.text.NumberFormat; 21 import java.text.ParsePosition; 22 23 import org.apache.commons.math.MathRuntimeException; 24 import org.apache.commons.math.util.MathUtils; 25 26 /** 27 * Formats a Fraction number in proper format. The number format for each of 28 * the whole number, numerator and, denominator can be configured. 29 * <p> 30 * Minus signs are only allowed in the whole number part - i.e., 31 * "-3 1/2" is legitimate and denotes -7/2, but "-3 -1/2" is invalid and 32 * will result in a <code>ParseException</code>.</p> 33 * 34 * @since 1.1 35 * @version $Revision: 762087 $ $Date: 2009-04-05 10:20:18 -0400 (Sun, 05 Apr 2009) $ 36 */ 37 public class ProperFractionFormat extends FractionFormat { 38 39 /** Serializable version identifier */ 40 private static final long serialVersionUID = 760934726031766749L; 41 42 /** The format used for the whole number. */ 43 private NumberFormat wholeFormat; 44 45 /** 46 * Create a proper formatting instance with the default number format for 47 * the whole, numerator, and denominator. 48 */ 49 public ProperFractionFormat() { 50 this(getDefaultNumberFormat()); 51 } 52 53 /** 54 * Create a proper formatting instance with a custom number format for the 55 * whole, numerator, and denominator. 56 * @param format the custom format for the whole, numerator, and 57 * denominator. 58 */ 59 public ProperFractionFormat(NumberFormat format) { 60 this(format, (NumberFormat)format.clone(), (NumberFormat)format.clone()); 61 } 62 63 /** 64 * Create a proper formatting instance with a custom number format for each 65 * of the whole, numerator, and denominator. 66 * @param wholeFormat the custom format for the whole. 67 * @param numeratorFormat the custom format for the numerator. 68 * @param denominatorFormat the custom format for the denominator. 69 */ 70 public ProperFractionFormat(NumberFormat wholeFormat, 71 NumberFormat numeratorFormat, 72 NumberFormat denominatorFormat) 73 { 74 super(numeratorFormat, denominatorFormat); 75 setWholeFormat(wholeFormat); 76 } 77 78 /** 79 * Formats a {@link Fraction} object to produce a string. The fraction 80 * is output in proper format. 81 * 82 * @param fraction the object to format. 83 * @param toAppendTo where the text is to be appended 84 * @param pos On input: an alignment field, if desired. On output: the 85 * offsets of the alignment field 86 * @return the value passed in as toAppendTo. 87 */ 88 @Override 89 public StringBuffer format(Fraction fraction, StringBuffer toAppendTo, 90 FieldPosition pos) { 91 92 pos.setBeginIndex(0); 93 pos.setEndIndex(0); 94 95 int num = fraction.getNumerator(); 96 int den = fraction.getDenominator(); 97 int whole = num / den; 98 num = num % den; 99 100 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 }