Source code

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
018package org.apache.commons.codec.language;
019
020import org.apache.commons.codec.EncoderException;
021import 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 * <p>This class is thread-safe.
028 * Although not strictly immutable, the mutable fields are not actually used.</p>
029 */
030public class Soundex implements StringEncoder {
031
032    /**
033     * The marker character used to indicate a silent (ignored) character.
034     * These are ignored except when they appear as the first character.
035     * <p>
036     * Note: the {@link #US_ENGLISH_MAPPING_STRING} does not use this mechanism
037     * because changing it might break existing code. Mappings that don't contain
038     * a silent marker code are treated as though H and W are silent.
039     * </p>
040     * <p>
041     * To override this, use the {@link #Soundex(String, boolean)} constructor.
042     * </p>
043     *
044     * @since 1.11
045     */
046    public static final char SILENT_MARKER = '-';
047
048    /**
049     * This is a default mapping of the 26 letters used in US English. A value of {@code 0} for a letter position
050     * means do not encode, but treat as a separator when it occurs between consonants with the same code.
051     * <p>
052     * (This constant is provided as both an implementation convenience and to allow Javadoc to pick
053     * up the value for the constant values page.)
054     * </p>
055     * <p>
056     * <b>Note that letters H and W are treated specially.</b>
057     * They are ignored (after the first letter) and don't act as separators
058     * between consonants with the same code.
059     * </p>
060     */
061    public static final String US_ENGLISH_MAPPING_STRING = "01230120022455012623010202";
062
063    /**
064     * This is a default mapping of the 26 letters used in US English. A value of {@code 0} for a letter position
065     * means do not encode.
066     *
067     * @see Soundex#Soundex(char[])
068     */
069    private static final char[] US_ENGLISH_MAPPING = US_ENGLISH_MAPPING_STRING.toCharArray();
070
071    /**
072     * An instance of Soundex using the US_ENGLISH_MAPPING mapping.
073     * This treats H and W as silent letters.
074     * Apart from when they appear as the first letter, they are ignored.
075     * They don't act as separators between duplicate codes.
076     *
077     * @see #US_ENGLISH_MAPPING_STRING
078     */
079    public static final Soundex US_ENGLISH = new Soundex();
080
081    /**
082     * An instance of Soundex using the Simplified Soundex mapping, as described here:
083     * http://west-penwith.org.uk/misc/soundex.htm
084     * <p>
085     * This treats H and W the same as vowels (AEIOUY).
086     * Such letters aren't encoded (after the first), but they do
087     * act as separators when dropping duplicate codes.
088     * The mapping is otherwise the same as for {@link #US_ENGLISH}
089     * </p>
090     *
091     * @since 1.11
092     */
093    public static final Soundex US_ENGLISH_SIMPLIFIED = new Soundex(US_ENGLISH_MAPPING_STRING, false);
094
095    /**
096     * An instance of Soundex using the mapping as per the Genealogy site:
097     * http://www.genealogy.com/articles/research/00000060.html
098     * <p>
099     * This treats vowels (AEIOUY), H and W as silent letters.
100     * Such letters are ignored (after the first) and do not
101     * act as separators when dropping duplicate codes.
102     * </p>
103     * <p>
104     * The codes for consonants are otherwise the same as for
105     * {@link #US_ENGLISH_MAPPING_STRING} and {@link #US_ENGLISH_SIMPLIFIED}
106     * </p>
107     *
108     * @since 1.11
109     */
110    public static final Soundex US_ENGLISH_GENEALOGY = new Soundex("-123-12--22455-12623-1-2-2");
111    //                                                              ABCDEFGHIJKLMNOPQRSTUVWXYZ
112
113    /**
114     * The maximum length of a Soundex code - Soundex codes are only four characters by definition.
115     *
116     * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
117     */
118    @Deprecated
119    private int maxLength = 4;
120
121    /**
122     * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each
123     * letter is mapped. This implementation contains a default map for US_ENGLISH
124     */
125    private final char[] soundexMapping;
126
127    /**
128     * Should H and W be treated specially?
129     * <p>
130     * In versions of the code prior to 1.11,
131     * the code always treated H and W as silent (ignored) letters.
132     * If this field is false, H and W are no longer special-cased.
133     * </p>
134     */
135    private final boolean specialCaseHW;
136
137    /**
138     * Creates an instance using US_ENGLISH_MAPPING
139     *
140     * @see Soundex#Soundex(char[])
141     * @see Soundex#US_ENGLISH_MAPPING_STRING
142     */
143    public Soundex() {
144        this.soundexMapping = US_ENGLISH_MAPPING;
145        this.specialCaseHW = true;
146    }
147
148    /**
149     * Creates a soundex instance using the given mapping. This constructor can be used to provide an internationalized
150     * mapping for a non-Western character set.
151     * <p>
152     * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each
153     * letter is mapped. This implementation contains a default map for US_ENGLISH
154     * </p>
155     * <p>
156     * If the mapping contains an instance of {@link #SILENT_MARKER} then H and W are not given special treatment
157     * </p>
158     *
159     * @param mapping
160     *                  Mapping array to use when finding the corresponding code for a given character
161     */
162    public Soundex(final char[] mapping) {
163        this.soundexMapping = mapping.clone();
164        this.specialCaseHW = !hasMarker(this.soundexMapping);
165    }
166
167    /**
168     * Creates a refined soundex instance using a custom mapping. This constructor can be used to customize the mapping,
169     * and/or possibly provide an internationalized mapping for a non-Western character set.
170     * <p>
171     * If the mapping contains an instance of {@link #SILENT_MARKER} then H and W are not given special treatment
172     * </p>
173     *
174     * @param mapping
175     *            Mapping string to use when finding the corresponding code for a given character
176     * @since 1.4
177     */
178    public Soundex(final String mapping) {
179        this.soundexMapping = mapping.toCharArray();
180        this.specialCaseHW = !hasMarker(this.soundexMapping);
181    }
182
183    /**
184     * Creates a refined soundex instance using a custom mapping. This constructor can be used to customize the mapping,
185     * and/or possibly provide an internationalized mapping for a non-Western character set.
186     *
187     * @param mapping
188     *            Mapping string to use when finding the corresponding code for a given character
189     * @param specialCaseHW if true, then
190     * @since 1.11
191     */
192    public Soundex(final String mapping, final boolean specialCaseHW) {
193        this.soundexMapping = mapping.toCharArray();
194        this.specialCaseHW = specialCaseHW;
195    }
196
197    /**
198     * Encodes the Strings and returns the number of characters in the two encoded Strings that are the same. This
199     * return value ranges from 0 through 4: 0 indicates little or no similarity, and 4 indicates strong similarity or
200     * identical values.
201     *
202     * @param s1
203     *                  A String that will be encoded and compared.
204     * @param s2
205     *                  A String that will be encoded and compared.
206     * @return The number of characters in the two encoded Strings that are the same from 0 to 4.
207     *
208     * @see SoundexUtils#difference(StringEncoder,String,String)
209     * @see <a href="https://msdn.microsoft.com/library/default.asp?url=/library/en-us/tsqlref/ts_de-dz_8co5.asp"> MS
210     *          T-SQL DIFFERENCE</a>
211     *
212     * @throws EncoderException
213     *                  if an error occurs encoding one of the strings
214     * @since 1.3
215     */
216    public int difference(final String s1, final String s2) throws EncoderException {
217        return SoundexUtils.difference(this, s1, s2);
218    }
219
220    /**
221     * Encodes an Object using the soundex algorithm. This method is provided in order to satisfy the requirements of
222     * the Encoder interface, and will throw an EncoderException if the supplied object is not of type {@link String}.
223     *
224     * @param obj
225     *                  Object to encode
226     * @return An object (or type {@link String}) containing the soundex code which corresponds to the String
227     *             supplied.
228     * @throws EncoderException
229     *                  if the parameter supplied is not of type {@link String}
230     * @throws IllegalArgumentException
231     *                  if a character is not mapped
232     */
233    @Override
234    public Object encode(final Object obj) throws EncoderException {
235        if (!(obj instanceof String)) {
236            throw new EncoderException("Parameter supplied to Soundex encode is not of type java.lang.String");
237        }
238        return soundex((String) obj);
239    }
240
241    /**
242     * Encodes a String using the soundex algorithm.
243     *
244     * @param str
245     *                  A String object to encode
246     * @return A Soundex code corresponding to the String supplied
247     * @throws IllegalArgumentException
248     *                  if a character is not mapped
249     */
250    @Override
251    public String encode(final String str) {
252        return soundex(str);
253    }
254
255    /**
256     * Returns the maxLength. Standard Soundex
257     *
258     * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
259     * @return int
260     */
261    @Deprecated
262    public int getMaxLength() {
263        return this.maxLength;
264    }
265
266    private boolean hasMarker(final char[] mapping) {
267        for (final char ch : mapping) {
268            if (ch == SILENT_MARKER) {
269                return true;
270            }
271        }
272        return false;
273    }
274
275    /**
276     * Maps the given upper-case character to its Soundex code.
277     *
278     * @param ch
279     *                  An upper-case character.
280     * @return A Soundex code.
281     * @throws IllegalArgumentException
282     *                  Thrown if {@code ch} is not mapped.
283     */
284    private char map(final char ch) {
285        final int index = ch - 'A';
286        if (index < 0 || index >= this.soundexMapping.length) {
287            throw new IllegalArgumentException("The character is not mapped: " + ch + " (index=" + index + ")");
288        }
289        return this.soundexMapping[index];
290    }
291
292    /**
293     * Sets the maxLength.
294     *
295     * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
296     * @param maxLength
297     *                  The maxLength to set
298     */
299    @Deprecated
300    public void setMaxLength(final int maxLength) {
301        this.maxLength = maxLength;
302    }
303
304    /**
305     * Retrieves the Soundex code for a given String object.
306     *
307     * @param str
308     *                  String to encode using the Soundex algorithm
309     * @return A soundex code for the String supplied
310     * @throws IllegalArgumentException
311     *                  if a character is not mapped
312     */
313    public String soundex(String str) {
314        if (str == null) {
315            return null;
316        }
317        str = SoundexUtils.clean(str);
318        if (str.isEmpty()) {
319            return str;
320        }
321        final char[] out = { '0', '0', '0', '0' };
322        int count = 0;
323        final char first = str.charAt(0);
324        out[count++] = first;
325        char lastDigit = map(first); // previous digit
326        for (int i = 1; i < str.length() && count < out.length; i++) {
327            final char ch = str.charAt(i);
328            if (this.specialCaseHW && (ch == 'H' || ch == 'W')) { // these are ignored completely
329                continue;
330            }
331            final char digit = map(ch);
332            if (digit == SILENT_MARKER) {
333                continue;
334            }
335            if (digit != '0' && digit != lastDigit) { // don't store vowels or repeats
336                out[count++] = digit;
337            }
338            lastDigit = digit;
339        }
340        return new String(out);
341    }
342
343}