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 java.util.regex.Pattern;
21
22 import org.apache.commons.codec.EncoderException;
23 import org.apache.commons.codec.StringEncoder;
24
25 /**
26 * Encodes a string into a NYSIIS value. NYSIIS is an encoding used to relate similar names, but can also be used as a
27 * general purpose scheme to find word with similar phonemes.
28 * <p>
29 * NYSIIS features an accuracy increase of 2.7% over the traditional Soundex algorithm.
30 * <p>
31 * Algorithm description:
32 * <pre>
33 * 1. Transcode first characters of name
34 * 1a. MAC -> MCC
35 * 1b. KN -> NN
36 * 1c. K -> C
37 * 1d. PH -> FF
38 * 1e. PF -> FF
39 * 1f. SCH -> SSS
40 * 2. Transcode last characters of name
41 * 2a. EE, IE -> Y
42 * 2b. DT,RT,RD,NT,ND -> D
43 * 3. First character of key = first character of name
44 * 4. Transcode remaining characters by following these rules, incrementing by one character each time
45 * 4a. EV -> AF else A,E,I,O,U -> A
46 * 4b. Q -> G
47 * 4c. Z -> S
48 * 4d. M -> N
49 * 4e. KN -> N else K -> C
50 * 4f. SCH -> SSS
51 * 4g. PH -> FF
52 * 4h. H -> If previous or next is nonvowel, previous
53 * 4i. W -> If previous is vowel, previous
54 * 4j. Add current to key if current != last key character
55 * 5. If last character is S, remove it
56 * 6. If last characters are AY, replace with Y
57 * 7. If last character is A, remove it
58 * 8. Collapse all strings of repeated characters
59 * 9. Add original first character of name as first character of key
60 * </pre>
61 * <p>
62 * This class is immutable and thread-safe.
63 *
64 * @see <a href="http://en.wikipedia.org/wiki/NYSIIS">NYSIIS on Wikipedia</a>
65 * @see <a href="http://www.dropby.com/NYSIIS.html">NYSIIS on dropby.com</a>
66 * @see Soundex
67 * @since 1.7
68 * @version $Id: Nysiis.html 891688 2013-12-24 20:49:46Z ggregory $
69 */
70 public class Nysiis implements StringEncoder {
71
72 private static final char[] CHARS_A = new char[] { 'A' };
73 private static final char[] CHARS_AF = new char[] { 'A', 'F' };
74 private static final char[] CHARS_C = new char[] { 'C' };
75 private static final char[] CHARS_FF = new char[] { 'F', 'F' };
76 private static final char[] CHARS_G = new char[] { 'G' };
77 private static final char[] CHARS_N = new char[] { 'N' };
78 private static final char[] CHARS_NN = new char[] { 'N', 'N' };
79 private static final char[] CHARS_S = new char[] { 'S' };
80 private static final char[] CHARS_SSS = new char[] { 'S', 'S', 'S' };
81
82 private static final Pattern PAT_MAC = Pattern.compile("^MAC");
83 private static final Pattern PAT_KN = Pattern.compile("^KN");
84 private static final Pattern PAT_K = Pattern.compile("^K");
85 private static final Pattern PAT_PH_PF = Pattern.compile("^(PH|PF)");
86 private static final Pattern PAT_SCH = Pattern.compile("^SCH");
87 private static final Pattern PAT_EE_IE = Pattern.compile("(EE|IE)$");
88 private static final Pattern PAT_DT_ETC = Pattern.compile("(DT|RT|RD|NT|ND)$");
89
90 private static final char SPACE = ' ';
91 private static final int TRUE_LENGTH = 6;
92
93 /**
94 * Tests if the given character is a vowel.
95 *
96 * @param c
97 * the character to test
98 * @return {@code true} if the character is a vowel, {@code false} otherwise
99 */
100 private static boolean isVowel(final char c) {
101 return c == 'A' || c == 'E' || c == 'I' || c == 'O' || c == 'U';
102 }
103
104 /**
105 * Transcodes the remaining parts of the String. The method operates on a sliding window, looking at 4 characters at
106 * a time: [i-1, i, i+1, i+2].
107 *
108 * @param prev
109 * the previous character
110 * @param curr
111 * the current character
112 * @param next
113 * the next character
114 * @param aNext
115 * the after next character
116 * @return a transcoded array of characters, starting from the current position
117 */
118 private static char[] transcodeRemaining(final char prev, final char curr, final char next, final char aNext) {
119 // 1. EV -> AF
120 if (curr == 'E' && next == 'V') {
121 return CHARS_AF;
122 }
123
124 // A, E, I, O, U -> A
125 if (isVowel(curr)) {
126 return CHARS_A;
127 }
128
129 // 2. Q -> G, Z -> S, M -> N
130 if (curr == 'Q') {
131 return CHARS_G;
132 } else if (curr == 'Z') {
133 return CHARS_S;
134 } else if (curr == 'M') {
135 return CHARS_N;
136 }
137
138 // 3. KN -> NN else K -> C
139 if (curr == 'K') {
140 if (next == 'N') {
141 return CHARS_NN;
142 } else {
143 return CHARS_C;
144 }
145 }
146
147 // 4. SCH -> SSS
148 if (curr == 'S' && next == 'C' && aNext == 'H') {
149 return CHARS_SSS;
150 }
151
152 // PH -> FF
153 if (curr == 'P' && next == 'H') {
154 return CHARS_FF;
155 }
156
157 // 5. H -> If previous or next is a non vowel, previous.
158 if (curr == 'H' && (!isVowel(prev) || !isVowel(next))) {
159 return new char[] { prev };
160 }
161
162 // 6. W -> If previous is vowel, previous.
163 if (curr == 'W' && isVowel(prev)) {
164 return new char[] { prev };
165 }
166
167 return new char[] { curr };
168 }
169
170 /** Indicates the strict mode. */
171 private final boolean strict;
172
173 /**
174 * Creates an instance of the {@link Nysiis} encoder with strict mode (original form),
175 * i.e. encoded strings have a maximum length of 6.
176 */
177 public Nysiis() {
178 this(true);
179 }
180
181 /**
182 * Create an instance of the {@link Nysiis} encoder with the specified strict mode:
183 *
184 * <ul>
185 * <li>{@code true}: encoded strings have a maximum length of 6</li>
186 * <li>{@code false}: encoded strings may have arbitrary length</li>
187 * </ul>
188 *
189 * @param strict
190 * the strict mode
191 */
192 public Nysiis(final boolean strict) {
193 this.strict = strict;
194 }
195
196 /**
197 * Encodes an Object using the NYSIIS algorithm. This method is provided in order to satisfy the requirements of the
198 * Encoder interface, and will throw an {@link EncoderException} if the supplied object is not of type
199 * {@link String}.
200 *
201 * @param obj
202 * Object to encode
203 * @return An object (or a {@link String}) containing the NYSIIS code which corresponds to the given String.
204 * @throws EncoderException
205 * if the parameter supplied is not of a {@link String}
206 * @throws IllegalArgumentException
207 * if a character is not mapped
208 */
209 @Override
210 public Object encode(final Object obj) throws EncoderException {
211 if (!(obj instanceof String)) {
212 throw new EncoderException("Parameter supplied to Nysiis encode is not of type java.lang.String");
213 }
214 return this.nysiis((String) obj);
215 }
216
217 /**
218 * Encodes a String using the NYSIIS algorithm.
219 *
220 * @param str
221 * A String object to encode
222 * @return A Nysiis code corresponding to the String supplied
223 * @throws IllegalArgumentException
224 * if a character is not mapped
225 */
226 @Override
227 public String encode(final String str) {
228 return this.nysiis(str);
229 }
230
231 /**
232 * Indicates the strict mode for this {@link Nysiis} encoder.
233 *
234 * @return {@code true} if the encoder is configured for strict mode, {@code false} otherwise
235 */
236 public boolean isStrict() {
237 return this.strict;
238 }
239
240 /**
241 * Retrieves the NYSIIS code for a given String object.
242 *
243 * @param str
244 * String to encode using the NYSIIS algorithm
245 * @return A NYSIIS code for the String supplied
246 */
247 public String nysiis(String str) {
248 if (str == null) {
249 return null;
250 }
251
252 // Use the same clean rules as Soundex
253 str = SoundexUtils.clean(str);
254
255 if (str.length() == 0) {
256 return str;
257 }
258
259 // Translate first characters of name:
260 // MAC -> MCC, KN -> NN, K -> C, PH | PF -> FF, SCH -> SSS
261 str = PAT_MAC.matcher(str).replaceFirst("MCC");
262 str = PAT_KN.matcher(str).replaceFirst("NN");
263 str = PAT_K.matcher(str).replaceFirst("C");
264 str = PAT_PH_PF.matcher(str).replaceFirst("FF");
265 str = PAT_SCH.matcher(str).replaceFirst("SSS");
266
267 // Translate last characters of name:
268 // EE -> Y, IE -> Y, DT | RT | RD | NT | ND -> D
269 str = PAT_EE_IE.matcher(str).replaceFirst("Y");
270 str = PAT_DT_ETC.matcher(str).replaceFirst("D");
271
272 // First character of key = first character of name.
273 final StringBuilder key = new StringBuilder(str.length());
274 key.append(str.charAt(0));
275
276 // Transcode remaining characters, incrementing by one character each time
277 final char[] chars = str.toCharArray();
278 final int len = chars.length;
279
280 for (int i = 1; i < len; i++) {
281 final char next = i < len - 1 ? chars[i + 1] : SPACE;
282 final char aNext = i < len - 2 ? chars[i + 2] : SPACE;
283 final char[] transcoded = transcodeRemaining(chars[i - 1], chars[i], next, aNext);
284 System.arraycopy(transcoded, 0, chars, i, transcoded.length);
285
286 // only append the current char to the key if it is different from the last one
287 if (chars[i] != chars[i - 1]) {
288 key.append(chars[i]);
289 }
290 }
291
292 if (key.length() > 1) {
293 char lastChar = key.charAt(key.length() - 1);
294
295 // If last character is S, remove it.
296 if (lastChar == 'S') {
297 key.deleteCharAt(key.length() - 1);
298 lastChar = key.charAt(key.length() - 1);
299 }
300
301 if (key.length() > 2) {
302 final char last2Char = key.charAt(key.length() - 2);
303 // If last characters are AY, replace with Y.
304 if (last2Char == 'A' && lastChar == 'Y') {
305 key.deleteCharAt(key.length() - 2);
306 }
307 }
308
309 // If last character is A, remove it.
310 if (lastChar == 'A') {
311 key.deleteCharAt(key.length() - 1);
312 }
313 }
314
315 final String string = key.toString();
316 return this.isStrict() ? string.substring(0, Math.min(TRUE_LENGTH, string.length())) : string;
317 }
318
319 }