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 1201529 2011-11-13 21:57:16Z 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 private 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 * The maximum length of a Soundex code - Soundex codes are only four characters by definition.
061 *
062 * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
063 */
064 private int maxLength = 4;
065
066 /**
067 * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each
068 * letter is mapped. This implementation contains a default map for US_ENGLISH
069 */
070 private final char[] soundexMapping;
071
072 /**
073 * Creates an instance using US_ENGLISH_MAPPING
074 *
075 * @see Soundex#Soundex(char[])
076 * @see Soundex#US_ENGLISH_MAPPING
077 */
078 public Soundex() {
079 this.soundexMapping = US_ENGLISH_MAPPING;
080 }
081
082 /**
083 * Creates a soundex instance using the given mapping. This constructor can be used to provide an internationalized
084 * mapping for a non-Western character set.
085 *
086 * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each
087 * letter is mapped. This implementation contains a default map for US_ENGLISH
088 *
089 * @param mapping
090 * Mapping array to use when finding the corresponding code for a given character
091 */
092 public Soundex(char[] mapping) {
093 this.soundexMapping = new char[mapping.length];
094 System.arraycopy(mapping, 0, this.soundexMapping, 0, mapping.length);
095 }
096
097 /**
098 * Creates a refined soundex instance using a custom mapping. This constructor can be used to customize the mapping,
099 * and/or possibly provide an internationalized mapping for a non-Western character set.
100 *
101 * @param mapping
102 * Mapping string to use when finding the corresponding code for a given character
103 * @since 1.4
104 */
105 public Soundex(String mapping) {
106 this.soundexMapping = mapping.toCharArray();
107 }
108
109 /**
110 * Encodes the Strings and returns the number of characters in the two encoded Strings that are the same. This
111 * return value ranges from 0 through 4: 0 indicates little or no similarity, and 4 indicates strong similarity or
112 * identical values.
113 *
114 * @param s1
115 * A String that will be encoded and compared.
116 * @param s2
117 * A String that will be encoded and compared.
118 * @return The number of characters in the two encoded Strings that are the same from 0 to 4.
119 *
120 * @see SoundexUtils#difference(StringEncoder,String,String)
121 * @see <a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/tsqlref/ts_de-dz_8co5.asp"> MS
122 * T-SQL DIFFERENCE </a>
123 *
124 * @throws EncoderException
125 * if an error occurs encoding one of the strings
126 * @since 1.3
127 */
128 public int difference(String s1, String s2) throws EncoderException {
129 return SoundexUtils.difference(this, s1, s2);
130 }
131
132 /**
133 * Encodes an Object using the soundex algorithm. This method is provided in order to satisfy the requirements of
134 * the Encoder interface, and will throw an EncoderException if the supplied object is not of type java.lang.String.
135 *
136 * @param pObject
137 * Object to encode
138 * @return An object (or type java.lang.String) containing the soundex code which corresponds to the String
139 * supplied.
140 * @throws EncoderException
141 * if the parameter supplied is not of type java.lang.String
142 * @throws IllegalArgumentException
143 * if a character is not mapped
144 */
145 public Object encode(Object pObject) throws EncoderException {
146 if (!(pObject instanceof String)) {
147 throw new EncoderException("Parameter supplied to Soundex encode is not of type java.lang.String");
148 }
149 return soundex((String) pObject);
150 }
151
152 /**
153 * Encodes a String using the soundex algorithm.
154 *
155 * @param pString
156 * A String object to encode
157 * @return A Soundex code corresponding to the String supplied
158 * @throws IllegalArgumentException
159 * if a character is not mapped
160 */
161 public String encode(String pString) {
162 return soundex(pString);
163 }
164
165 /**
166 * Used internally by the SoundEx algorithm.
167 *
168 * Consonants from the same code group separated by W or H are treated as one.
169 *
170 * @param str
171 * the cleaned working string to encode (in upper case).
172 * @param index
173 * the character position to encode
174 * @return Mapping code for a particular character
175 * @throws IllegalArgumentException
176 * if the character is not mapped
177 */
178 private char getMappingCode(String str, int index) {
179 // map() throws IllegalArgumentException
180 char mappedChar = this.map(str.charAt(index));
181 // HW rule check
182 if (index > 1 && mappedChar != '0') {
183 char hwChar = str.charAt(index - 1);
184 if ('H' == hwChar || 'W' == hwChar) {
185 char preHWChar = str.charAt(index - 2);
186 char firstCode = this.map(preHWChar);
187 if (firstCode == mappedChar || 'H' == preHWChar || 'W' == preHWChar) {
188 return 0;
189 }
190 }
191 }
192 return mappedChar;
193 }
194
195 /**
196 * Returns the maxLength. Standard Soundex
197 *
198 * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
199 * @return int
200 */
201 public int getMaxLength() {
202 return this.maxLength;
203 }
204
205 /**
206 * Returns the soundex mapping.
207 *
208 * @return soundexMapping.
209 */
210 private char[] getSoundexMapping() {
211 return this.soundexMapping;
212 }
213
214 /**
215 * Maps the given upper-case character to its Soundex code.
216 *
217 * @param ch
218 * An upper-case character.
219 * @return A Soundex code.
220 * @throws IllegalArgumentException
221 * Thrown if <code>ch</code> is not mapped.
222 */
223 private char map(char ch) {
224 int index = ch - 'A';
225 if (index < 0 || index >= this.getSoundexMapping().length) {
226 throw new IllegalArgumentException("The character is not mapped: " + ch);
227 }
228 return this.getSoundexMapping()[index];
229 }
230
231 /**
232 * Sets the maxLength.
233 *
234 * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
235 * @param maxLength
236 * The maxLength to set
237 */
238 public void setMaxLength(int maxLength) {
239 this.maxLength = maxLength;
240 }
241
242 /**
243 * Retrieves the Soundex code for a given String object.
244 *
245 * @param str
246 * String to encode using the Soundex algorithm
247 * @return A soundex code for the String supplied
248 * @throws IllegalArgumentException
249 * if a character is not mapped
250 */
251 public String soundex(String str) {
252 if (str == null) {
253 return null;
254 }
255 str = SoundexUtils.clean(str);
256 if (str.length() == 0) {
257 return str;
258 }
259 char out[] = {'0', '0', '0', '0'};
260 char last, mapped;
261 int incount = 1, count = 1;
262 out[0] = str.charAt(0);
263 // getMappingCode() throws IllegalArgumentException
264 last = getMappingCode(str, 0);
265 while ((incount < str.length()) && (count < out.length)) {
266 mapped = getMappingCode(str, incount++);
267 if (mapped != 0) {
268 if ((mapped != '0') && (mapped != last)) {
269 out[count++] = mapped;
270 }
271 last = mapped;
272 }
273 }
274 return new String(out);
275 }
276
277 }