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.util.MathUtils; 24 25 /** 26 * Formats a Fraction number in proper format. The number format for each of 27 * the whole number, numerator and, denominator can be configured. 28 * <p> 29 * Minus signs are only allowed in the whole number part - i.e., 30 * "-3 1/2" is legitimate and denotes -7/2, but "-3 -1/2" is invalid and 31 * will result in a <code>ParseException</code>.</p> 32 * 33 * @since 1.1 34 * @version $Revision: 617953 $ $Date: 2008-02-02 22:54:00 -0700 (Sat, 02 Feb 2008) $ 35 */ 36 public class ProperFractionFormat extends FractionFormat { 37 38 /** Serializable version identifier */ 39 private static final long serialVersionUID = -6337346779577272307L; 40 41 /** The format used for the whole number. */ 42 private NumberFormat wholeFormat; 43 44 /** 45 * Create a proper formatting instance with the default number format for 46 * the whole, numerator, and denominator. 47 */ 48 public ProperFractionFormat() { 49 this(getDefaultNumberFormat()); 50 } 51 52 /** 53 * Create a proper formatting instance with a custom number format for the 54 * whole, numerator, and denominator. 55 * @param format the custom format for the whole, numerator, and 56 * denominator. 57 */ 58 public ProperFractionFormat(NumberFormat format) { 59 this(format, (NumberFormat)format.clone(), (NumberFormat)format.clone()); 60 } 61 62 /** 63 * Create a proper formatting instance with a custom number format for each 64 * of the whole, numerator, and denominator. 65 * @param wholeFormat the custom format for the whole. 66 * @param numeratorFormat the custom format for the numerator. 67 * @param denominatorFormat the custom format for the denominator. 68 */ 69 public ProperFractionFormat(NumberFormat wholeFormat, 70 NumberFormat numeratorFormat, 71 NumberFormat denominatorFormat) 72 { 73 super(numeratorFormat, denominatorFormat); 74 setWholeFormat(wholeFormat); 75 } 76 77 /** 78 * Formats a {@link Fraction} object to produce a string. The fraction 79 * is output in proper format. 80 * 81 * @param fraction the object to format. 82 * @param toAppendTo where the text is to be appended 83 * @param pos On input: an alignment field, if desired. On output: the 84 * offsets of the alignment field 85 * @return the value passed in as toAppendTo. 86 */ 87 public StringBuffer format(Fraction fraction, StringBuffer toAppendTo, 88 FieldPosition pos) { 89 90 pos.setBeginIndex(0); 91 pos.setEndIndex(0); 92 93 int num = fraction.getNumerator(); 94 int den = fraction.getDenominator(); 95 int whole = num / den; 96 num = num % den; 97 98 if (whole != 0) { 99 getWholeFormat().format(whole, toAppendTo, pos); 100 toAppendTo.append(' '); 101 num = Math.abs(num); 102 } 103 getNumeratorFormat().format(num, toAppendTo, pos); 104 toAppendTo.append(" / "); 105 getDenominatorFormat().format(den, toAppendTo, 106 pos); 107 108 return toAppendTo; 109 } 110 111 /** 112 * Access the whole format. 113 * @return the whole format. 114 */ 115 public NumberFormat getWholeFormat() { 116 return wholeFormat; 117 } 118 119 /** 120 * Parses a string to produce a {@link Fraction} object. This method 121 * expects the string to be formatted as a proper fraction. 122 * <p> 123 * Minus signs are only allowed in the whole number part - i.e., 124 * "-3 1/2" is legitimate and denotes -7/2, but "-3 -1/2" is invalid and 125 * will result in a <code>ParseException</code>.</p> 126 * 127 * @param source the string to parse 128 * @param pos input/ouput parsing parameter. 129 * @return the parsed {@link Fraction} object. 130 */ 131 public Fraction parse(String source, ParsePosition pos) { 132 // try to parse improper fraction 133 Fraction ret = super.parse(source, pos); 134 if (ret != null) { 135 return ret; 136 } 137 138 int initialIndex = pos.getIndex(); 139 140 // parse whitespace 141 parseAndIgnoreWhitespace(source, pos); 142 143 // parse whole 144 Number whole = getWholeFormat().parse(source, pos); 145 if (whole == null) { 146 // invalid integer number 147 // set index back to initial, error index should already be set 148 // character examined. 149 pos.setIndex(initialIndex); 150 return null; 151 } 152 153 // parse whitespace 154 parseAndIgnoreWhitespace(source, pos); 155 156 // parse numerator 157 Number num = getNumeratorFormat().parse(source, pos); 158 if (num == null) { 159 // invalid integer number 160 // set index back to initial, error index should already be set 161 // character examined. 162 pos.setIndex(initialIndex); 163 return null; 164 } 165 166 if (num.intValue() < 0) { 167 // minus signs should be leading, invalid expression 168 pos.setIndex(initialIndex); 169 return null; 170 } 171 172 // parse '/' 173 int startIndex = pos.getIndex(); 174 char c = parseNextCharacter(source, pos); 175 switch (c) { 176 case 0 : 177 // no '/' 178 // return num as a fraction 179 return new Fraction(num.intValue(), 1); 180 case '/' : 181 // found '/', continue parsing denominator 182 break; 183 default : 184 // invalid '/' 185 // set index back to initial, error index should be the last 186 // character examined. 187 pos.setIndex(initialIndex); 188 pos.setErrorIndex(startIndex); 189 return null; 190 } 191 192 // parse whitespace 193 parseAndIgnoreWhitespace(source, pos); 194 195 // parse denominator 196 Number den = getDenominatorFormat().parse(source, pos); 197 if (den == null) { 198 // invalid integer number 199 // set index back to initial, error index should already be set 200 // character examined. 201 pos.setIndex(initialIndex); 202 return null; 203 } 204 205 if (den.intValue() < 0) { 206 // minus signs must be leading, invalid 207 pos.setIndex(initialIndex); 208 return null; 209 } 210 211 int w = whole.intValue(); 212 int n = num.intValue(); 213 int d = den.intValue(); 214 return new Fraction(((Math.abs(w) * d) + n) * MathUtils.sign(w), d); 215 } 216 217 /** 218 * Modify the whole format. 219 * @param format The new whole format value. 220 * @throws IllegalArgumentException if <code>format</code> is 221 * <code>null</code>. 222 */ 223 public void setWholeFormat(NumberFormat format) { 224 if (format == null) { 225 throw new IllegalArgumentException( 226 "whole format can not be null."); 227 } 228 this.wholeFormat = format; 229 } 230 }