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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  
18  package org.apache.commons.codec.language;
19  
20  import org.apache.commons.codec.EncoderException;
21  import org.apache.commons.codec.StringEncoder;
22  
23  /**
24   * Encodes a string into a Soundex value. Soundex is an encoding used to relate similar names, but can also be used as a
25   * general purpose scheme to find word with similar phonemes.
26   *
27   * This class is thread-safe.
28   * Although not strictly immutable, the {@link #maxLength} field is not actually used.
29   *
30   * @version $Id: Soundex.java 1429868 2013-01-07 16:08:05Z ggregory $
31   */
32  public class Soundex implements StringEncoder {
33  
34      /**
35       * This is a default mapping of the 26 letters used in US English. A value of <code>0</code> for a letter position
36       * means do not encode.
37       * <p>
38       * (This constant is provided as both an implementation convenience and to allow Javadoc to pick
39       * up the value for the constant values page.)
40       * </p>
41       *
42       * @see #US_ENGLISH_MAPPING
43       */
44      public static final String US_ENGLISH_MAPPING_STRING = "01230120022455012623010202";
45  
46      /**
47       * This is a default mapping of the 26 letters used in US English. A value of <code>0</code> for a letter position
48       * means do not encode.
49       *
50       * @see Soundex#Soundex(char[])
51       */
52      private static final char[] US_ENGLISH_MAPPING = US_ENGLISH_MAPPING_STRING.toCharArray();
53  
54      /**
55       * An instance of Soundex using the US_ENGLISH_MAPPING mapping.
56       *
57       * @see #US_ENGLISH_MAPPING
58       */
59      public static final Soundex US_ENGLISH = new Soundex();
60  
61      /**
62       * The maximum length of a Soundex code - Soundex codes are only four characters by definition.
63       *
64       * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
65       */
66      @Deprecated
67      private int maxLength = 4;
68  
69      /**
70       * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each
71       * letter is mapped. This implementation contains a default map for US_ENGLISH
72       */
73      private final char[] soundexMapping;
74  
75      /**
76       * Creates an instance using US_ENGLISH_MAPPING
77       *
78       * @see Soundex#Soundex(char[])
79       * @see Soundex#US_ENGLISH_MAPPING
80       */
81      public Soundex() {
82          this.soundexMapping = US_ENGLISH_MAPPING;
83      }
84  
85      /**
86       * Creates a soundex instance using the given mapping. This constructor can be used to provide an internationalized
87       * mapping for a non-Western character set.
88       *
89       * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each
90       * letter is mapped. This implementation contains a default map for US_ENGLISH
91       *
92       * @param mapping
93       *                  Mapping array to use when finding the corresponding code for a given character
94       */
95      public Soundex(final char[] mapping) {
96          this.soundexMapping = new char[mapping.length];
97          System.arraycopy(mapping, 0, this.soundexMapping, 0, mapping.length);
98      }
99  
100     /**
101      * Creates a refined soundex instance using a custom mapping. This constructor can be used to customize the mapping,
102      * and/or possibly provide an internationalized mapping for a non-Western character set.
103      *
104      * @param mapping
105      *            Mapping string to use when finding the corresponding code for a given character
106      * @since 1.4
107      */
108     public Soundex(final String mapping) {
109         this.soundexMapping = mapping.toCharArray();
110     }
111 
112     /**
113      * Encodes the Strings and returns the number of characters in the two encoded Strings that are the same. This
114      * return value ranges from 0 through 4: 0 indicates little or no similarity, and 4 indicates strong similarity or
115      * identical values.
116      *
117      * @param s1
118      *                  A String that will be encoded and compared.
119      * @param s2
120      *                  A String that will be encoded and compared.
121      * @return The number of characters in the two encoded Strings that are the same from 0 to 4.
122      *
123      * @see SoundexUtils#difference(StringEncoder,String,String)
124      * @see <a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/tsqlref/ts_de-dz_8co5.asp"> MS
125      *          T-SQL DIFFERENCE </a>
126      *
127      * @throws EncoderException
128      *                  if an error occurs encoding one of the strings
129      * @since 1.3
130      */
131     public int difference(final String s1, final String s2) throws EncoderException {
132         return SoundexUtils.difference(this, s1, s2);
133     }
134 
135     /**
136      * Encodes an Object using the soundex algorithm. This method is provided in order to satisfy the requirements of
137      * the Encoder interface, and will throw an EncoderException if the supplied object is not of type java.lang.String.
138      *
139      * @param obj
140      *                  Object to encode
141      * @return An object (or type java.lang.String) containing the soundex code which corresponds to the String
142      *             supplied.
143      * @throws EncoderException
144      *                  if the parameter supplied is not of type java.lang.String
145      * @throws IllegalArgumentException
146      *                  if a character is not mapped
147      */
148     @Override
149     public Object encode(final Object obj) throws EncoderException {
150         if (!(obj instanceof String)) {
151             throw new EncoderException("Parameter supplied to Soundex encode is not of type java.lang.String");
152         }
153         return soundex((String) obj);
154     }
155 
156     /**
157      * Encodes a String using the soundex algorithm.
158      *
159      * @param str
160      *                  A String object to encode
161      * @return A Soundex code corresponding to the String supplied
162      * @throws IllegalArgumentException
163      *                  if a character is not mapped
164      */
165     @Override
166     public String encode(final String str) {
167         return soundex(str);
168     }
169 
170     /**
171      * Used internally by the SoundEx algorithm.
172      *
173      * Consonants from the same code group separated by W or H are treated as one.
174      *
175      * @param str
176      *                  the cleaned working string to encode (in upper case).
177      * @param index
178      *                  the character position to encode
179      * @return Mapping code for a particular character
180      * @throws IllegalArgumentException
181      *                  if the character is not mapped
182      */
183     private char getMappingCode(final String str, final int index) {
184         // map() throws IllegalArgumentException
185         final char mappedChar = this.map(str.charAt(index));
186         // HW rule check
187         if (index > 1 && mappedChar != '0') {
188             final char hwChar = str.charAt(index - 1);
189             if ('H' == hwChar || 'W' == hwChar) {
190                 final char preHWChar = str.charAt(index - 2);
191                 final char firstCode = this.map(preHWChar);
192                 if (firstCode == mappedChar || 'H' == preHWChar || 'W' == preHWChar) {
193                     return 0;
194                 }
195             }
196         }
197         return mappedChar;
198     }
199 
200     /**
201      * Returns the maxLength. Standard Soundex
202      *
203      * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
204      * @return int
205      */
206     @Deprecated
207     public int getMaxLength() {
208         return this.maxLength;
209     }
210 
211     /**
212      * Returns the soundex mapping.
213      *
214      * @return soundexMapping.
215      */
216     private char[] getSoundexMapping() {
217         return this.soundexMapping;
218     }
219 
220     /**
221      * Maps the given upper-case character to its Soundex code.
222      *
223      * @param ch
224      *                  An upper-case character.
225      * @return A Soundex code.
226      * @throws IllegalArgumentException
227      *                  Thrown if <code>ch</code> is not mapped.
228      */
229     private char map(final char ch) {
230         final int index = ch - 'A';
231         if (index < 0 || index >= this.getSoundexMapping().length) {
232             throw new IllegalArgumentException("The character is not mapped: " + ch);
233         }
234         return this.getSoundexMapping()[index];
235     }
236 
237     /**
238      * Sets the maxLength.
239      *
240      * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
241      * @param maxLength
242      *                  The maxLength to set
243      */
244     @Deprecated
245     public void setMaxLength(final int maxLength) {
246         this.maxLength = maxLength;
247     }
248 
249     /**
250      * Retrieves the Soundex code for a given String object.
251      *
252      * @param str
253      *                  String to encode using the Soundex algorithm
254      * @return A soundex code for the String supplied
255      * @throws IllegalArgumentException
256      *                  if a character is not mapped
257      */
258     public String soundex(String str) {
259         if (str == null) {
260             return null;
261         }
262         str = SoundexUtils.clean(str);
263         if (str.length() == 0) {
264             return str;
265         }
266         final char out[] = {'0', '0', '0', '0'};
267         char last, mapped;
268         int incount = 1, count = 1;
269         out[0] = str.charAt(0);
270         // getMappingCode() throws IllegalArgumentException
271         last = getMappingCode(str, 0);
272         while (incount < str.length() && count < out.length) {
273             mapped = getMappingCode(str, incount++);
274             if (mapped != 0) {
275                 if (mapped != '0' && mapped != last) {
276                     out[count++] = mapped;
277                 }
278                 last = mapped;
279             }
280         }
281         return new String(out);
282     }
283 
284 }