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 */ 017 018 package org.apache.commons.codec.language; 019 020 import org.apache.commons.codec.EncoderException; 021 import org.apache.commons.codec.StringEncoder; 022 023 /** 024 * Encodes a string into a Soundex value. Soundex is an encoding used to relate similar names, but can also be used as a 025 * general purpose scheme to find word with similar phonemes. 026 * 027 * @author Apache Software Foundation 028 * @version $Id: Soundex.java 794026 2009-07-14 19:21:23Z ggregory $ 029 */ 030 public class Soundex implements StringEncoder { 031 032 /** 033 * This is a default mapping of the 26 letters used in US English. A value of <code>0</code> for a letter position 034 * means do not encode. 035 * <p> 036 * (This constant is provided as both an implementation convenience and to allow Javadoc to pick 037 * up the value for the constant values page.) 038 * </p> 039 * 040 * @see #US_ENGLISH_MAPPING 041 */ 042 public static final String US_ENGLISH_MAPPING_STRING = "01230120022455012623010202"; 043 044 /** 045 * This is a default mapping of the 26 letters used in US English. A value of <code>0</code> for a letter position 046 * means do not encode. 047 * 048 * @see Soundex#Soundex(char[]) 049 */ 050 public static final char[] US_ENGLISH_MAPPING = US_ENGLISH_MAPPING_STRING.toCharArray(); 051 052 /** 053 * An instance of Soundex using the US_ENGLISH_MAPPING mapping. 054 * 055 * @see #US_ENGLISH_MAPPING 056 */ 057 public static final Soundex US_ENGLISH = new Soundex(); 058 059 060 /** 061 * Encodes the Strings and returns the number of characters in the two encoded Strings that are the same. This 062 * return value ranges from 0 through 4: 0 indicates little or no similarity, and 4 indicates strong similarity or 063 * identical values. 064 * 065 * @param s1 066 * A String that will be encoded and compared. 067 * @param s2 068 * A String that will be encoded and compared. 069 * @return The number of characters in the two encoded Strings that are the same from 0 to 4. 070 * 071 * @see SoundexUtils#difference(StringEncoder,String,String) 072 * @see <a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/tsqlref/ts_de-dz_8co5.asp"> MS 073 * T-SQL DIFFERENCE </a> 074 * 075 * @throws EncoderException 076 * if an error occurs encoding one of the strings 077 * @since 1.3 078 */ 079 public int difference(String s1, String s2) throws EncoderException { 080 return SoundexUtils.difference(this, s1, s2); 081 } 082 083 /** 084 * The maximum length of a Soundex code - Soundex codes are only four characters by definition. 085 * 086 * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0. 087 */ 088 private int maxLength = 4; 089 090 /** 091 * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each 092 * letter is mapped. This implementation contains a default map for US_ENGLISH 093 */ 094 private final char[] soundexMapping; 095 096 /** 097 * Creates an instance using US_ENGLISH_MAPPING 098 * 099 * @see Soundex#Soundex(char[]) 100 * @see Soundex#US_ENGLISH_MAPPING 101 */ 102 public Soundex() { 103 this.soundexMapping = US_ENGLISH_MAPPING; 104 } 105 106 /** 107 * Creates a soundex instance using the given mapping. This constructor can be used to provide an internationalized 108 * mapping for a non-Western character set. 109 * 110 * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each 111 * letter is mapped. This implementation contains a default map for US_ENGLISH 112 * 113 * @param mapping 114 * Mapping array to use when finding the corresponding code for a given character 115 */ 116 public Soundex(char[] mapping) { 117 this.soundexMapping = new char[mapping.length]; 118 System.arraycopy(mapping, 0, this.soundexMapping, 0, mapping.length); 119 } 120 121 /** 122 * Creates a refined soundex instance using a custom mapping. This constructor can be used to customize the mapping, 123 * and/or possibly provide an internationalized mapping for a non-Western character set. 124 * 125 * @param mapping 126 * Mapping string to use when finding the corresponding code for a given character 127 * @since 1.4 128 */ 129 public Soundex(String mapping) { 130 this.soundexMapping = mapping.toCharArray(); 131 } 132 133 /** 134 * Encodes an Object using the soundex algorithm. This method is provided in order to satisfy the requirements of 135 * the Encoder interface, and will throw an EncoderException if the supplied object is not of type java.lang.String. 136 * 137 * @param pObject 138 * Object to encode 139 * @return An object (or type java.lang.String) containing the soundex code which corresponds to the String 140 * supplied. 141 * @throws EncoderException 142 * if the parameter supplied is not of type java.lang.String 143 * @throws IllegalArgumentException 144 * if a character is not mapped 145 */ 146 public Object encode(Object pObject) throws EncoderException { 147 if (!(pObject instanceof String)) { 148 throw new EncoderException("Parameter supplied to Soundex encode is not of type java.lang.String"); 149 } 150 return soundex((String) pObject); 151 } 152 153 /** 154 * Encodes a String using the soundex algorithm. 155 * 156 * @param pString 157 * A String object to encode 158 * @return A Soundex code corresponding to the String supplied 159 * @throws IllegalArgumentException 160 * if a character is not mapped 161 */ 162 public String encode(String pString) { 163 return soundex(pString); 164 } 165 166 /** 167 * Used internally by the SoundEx algorithm. 168 * 169 * Consonants from the same code group separated by W or H are treated as one. 170 * 171 * @param str 172 * the cleaned working string to encode (in upper case). 173 * @param index 174 * the character position to encode 175 * @return Mapping code for a particular character 176 * @throws IllegalArgumentException 177 * if the character is not mapped 178 */ 179 private char getMappingCode(String str, int index) { 180 // map() throws IllegalArgumentException 181 char mappedChar = this.map(str.charAt(index)); 182 // HW rule check 183 if (index > 1 && mappedChar != '0') { 184 char hwChar = str.charAt(index - 1); 185 if ('H' == hwChar || 'W' == hwChar) { 186 char preHWChar = str.charAt(index - 2); 187 char firstCode = this.map(preHWChar); 188 if (firstCode == mappedChar || 'H' == preHWChar || 'W' == preHWChar) { 189 return 0; 190 } 191 } 192 } 193 return mappedChar; 194 } 195 196 /** 197 * Returns the maxLength. Standard Soundex 198 * 199 * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0. 200 * @return int 201 */ 202 public int getMaxLength() { 203 return this.maxLength; 204 } 205 206 /** 207 * Returns the soundex mapping. 208 * 209 * @return soundexMapping. 210 */ 211 private char[] getSoundexMapping() { 212 return this.soundexMapping; 213 } 214 215 /** 216 * Maps the given upper-case character to its Soundex code. 217 * 218 * @param ch 219 * An upper-case character. 220 * @return A Soundex code. 221 * @throws IllegalArgumentException 222 * Thrown if <code>ch</code> is not mapped. 223 */ 224 private char map(char ch) { 225 int index = ch - 'A'; 226 if (index < 0 || index >= this.getSoundexMapping().length) { 227 throw new IllegalArgumentException("The character is not mapped: " + ch); 228 } 229 return this.getSoundexMapping()[index]; 230 } 231 232 /** 233 * Sets the maxLength. 234 * 235 * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0. 236 * @param maxLength 237 * The maxLength to set 238 */ 239 public void setMaxLength(int maxLength) { 240 this.maxLength = maxLength; 241 } 242 243 /** 244 * Retrieves the Soundex code for a given String object. 245 * 246 * @param str 247 * String to encode using the Soundex algorithm 248 * @return A soundex code for the String supplied 249 * @throws IllegalArgumentException 250 * if a character is not mapped 251 */ 252 public String soundex(String str) { 253 if (str == null) { 254 return null; 255 } 256 str = SoundexUtils.clean(str); 257 if (str.length() == 0) { 258 return str; 259 } 260 char out[] = {'0', '0', '0', '0'}; 261 char last, mapped; 262 int incount = 1, count = 1; 263 out[0] = str.charAt(0); 264 // getMappingCode() throws IllegalArgumentException 265 last = getMappingCode(str, 0); 266 while ((incount < str.length()) && (count < out.length)) { 267 mapped = getMappingCode(str, incount++); 268 if (mapped != 0) { 269 if ((mapped != '0') && (mapped != last)) { 270 out[count++] = mapped; 271 } 272 last = mapped; 273 } 274 } 275 return new String(out); 276 } 277 278 }