Source Code Cross Referenced for Metaphone.java in  » Library » Apache-common-codec » org » apache » commons » codec » language » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Library » Apache common codec » org.apache.commons.codec.language 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         * Copyright 2001-2004 The Apache Software Foundation.
003:         * 
004:         * Licensed under the Apache License, Version 2.0 (the "License");
005:         * you may not use this file except in compliance with the License.
006:         * You may obtain a copy of the License at
007:         * 
008:         *      http://www.apache.org/licenses/LICENSE-2.0
009:         * 
010:         * Unless required by applicable law or agreed to in writing, software
011:         * distributed under the License is distributed on an "AS IS" BASIS,
012:         * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013:         * See the License for the specific language governing permissions and
014:         * limitations under the License.
015:         */
016:
017:        package org.apache.commons.codec.language;
018:
019:        import org.apache.commons.codec.EncoderException;
020:        import org.apache.commons.codec.StringEncoder;
021:
022:        /**
023:         * Encodes a string into a metaphone value. 
024:         * <p>
025:         * Initial Java implementation by <CITE>William B. Brogden. December, 1997</CITE>. 
026:         * Permission given by <CITE>wbrogden</CITE> for code to be used anywhere.
027:         * </p>
028:         * <p>
029:         * <CITE>Hanging on the Metaphone</CITE> by <CITE>Lawrence Philips</CITE> in <CITE>Computer Language of Dec. 1990, p
030:         * 39.</CITE>
031:         * </p>
032:         * 
033:         * @author Apache Software Foundation
034:         * @version $Id: Metaphone.java,v 1.20 2004/06/05 18:32:04 ggregory Exp $
035:         */
036:        public class Metaphone implements  StringEncoder {
037:
038:            /**
039:             * Five values in the English language 
040:             */
041:            private String vowels = "AEIOU";
042:
043:            /**
044:             * Variable used in Metaphone algorithm
045:             */
046:            private String frontv = "EIY";
047:
048:            /**
049:             * Variable used in Metaphone algorithm
050:             */
051:            private String varson = "CSPTG";
052:
053:            /**
054:             * The max code length for metaphone is 4
055:             */
056:            private int maxCodeLen = 4;
057:
058:            /**
059:             * Creates an instance of the Metaphone encoder
060:             */
061:            public Metaphone() {
062:                super ();
063:            }
064:
065:            /**
066:             * Find the metaphone value of a String. This is similar to the
067:             * soundex algorithm, but better at finding similar sounding words.
068:             * All input is converted to upper case.
069:             * Limitations: Input format is expected to be a single ASCII word
070:             * with only characters in the A - Z range, no punctuation or numbers.
071:             *
072:             * @param txt String to find the metaphone code for
073:             * @return A metaphone code corresponding to the String supplied
074:             */
075:            public String metaphone(String txt) {
076:                boolean hard = false;
077:                if ((txt == null) || (txt.length() == 0)) {
078:                    return "";
079:                }
080:                // single character is itself
081:                if (txt.length() == 1) {
082:                    return txt.toUpperCase();
083:                }
084:
085:                char[] inwd = txt.toUpperCase().toCharArray();
086:
087:                StringBuffer local = new StringBuffer(40); // manipulate
088:                StringBuffer code = new StringBuffer(10); //   output
089:                // handle initial 2 characters exceptions
090:                switch (inwd[0]) {
091:                case 'K':
092:                case 'G':
093:                case 'P': /* looking for KN, etc*/
094:                    if (inwd[1] == 'N') {
095:                        local.append(inwd, 1, inwd.length - 1);
096:                    } else {
097:                        local.append(inwd);
098:                    }
099:                    break;
100:                case 'A': /* looking for AE */
101:                    if (inwd[1] == 'E') {
102:                        local.append(inwd, 1, inwd.length - 1);
103:                    } else {
104:                        local.append(inwd);
105:                    }
106:                    break;
107:                case 'W': /* looking for WR or WH */
108:                    if (inwd[1] == 'R') { // WR -> R
109:                        local.append(inwd, 1, inwd.length - 1);
110:                        break;
111:                    }
112:                    if (inwd[1] == 'H') {
113:                        local.append(inwd, 1, inwd.length - 1);
114:                        local.setCharAt(0, 'W'); // WH -> W
115:                    } else {
116:                        local.append(inwd);
117:                    }
118:                    break;
119:                case 'X': /* initial X becomes S */
120:                    inwd[0] = 'S';
121:                    local.append(inwd);
122:                    break;
123:                default:
124:                    local.append(inwd);
125:                } // now local has working string with initials fixed
126:
127:                int wdsz = local.length();
128:                int n = 0;
129:
130:                while ((code.length() < this .getMaxCodeLen()) && (n < wdsz)) { // max code size of 4 works well
131:                    char symb = local.charAt(n);
132:                    // remove duplicate letters except C
133:                    if ((symb != 'C') && (isPreviousChar(local, n, symb))) {
134:                        n++;
135:                    } else { // not dup
136:                        switch (symb) {
137:                        case 'A':
138:                        case 'E':
139:                        case 'I':
140:                        case 'O':
141:                        case 'U':
142:                            if (n == 0) {
143:                                code.append(symb);
144:                            }
145:                            break; // only use vowel if leading char
146:                        case 'B':
147:                            if (isPreviousChar(local, n, 'M')
148:                                    && isLastChar(wdsz, n)) { // B is silent if word ends in MB
149:                                break;
150:                            }
151:                            code.append(symb);
152:                            break;
153:                        case 'C': // lots of C special cases
154:                            /* discard if SCI, SCE or SCY */
155:                            if (isPreviousChar(local, n, 'S')
156:                                    && !isLastChar(wdsz, n)
157:                                    && (this .frontv
158:                                            .indexOf(local.charAt(n + 1)) >= 0)) {
159:                                break;
160:                            }
161:                            if (regionMatch(local, n, "CIA")) { // "CIA" -> X
162:                                code.append('X');
163:                                break;
164:                            }
165:                            if (!isLastChar(wdsz, n)
166:                                    && (this .frontv
167:                                            .indexOf(local.charAt(n + 1)) >= 0)) {
168:                                code.append('S');
169:                                break; // CI,CE,CY -> S
170:                            }
171:                            if (isPreviousChar(local, n, 'S')
172:                                    && isNextChar(local, n, 'H')) { // SCH->sk
173:                                code.append('K');
174:                                break;
175:                            }
176:                            if (isNextChar(local, n, 'H')) { // detect CH
177:                                if ((n == 0) && (wdsz >= 3)
178:                                        && isVowel(local, 2)) { // CH consonant -> K consonant
179:                                    code.append('K');
180:                                } else {
181:                                    code.append('X'); // CHvowel -> X
182:                                }
183:                            } else {
184:                                code.append('K');
185:                            }
186:                            break;
187:                        case 'D':
188:                            if (!isLastChar(wdsz, n + 1)
189:                                    && isNextChar(local, n, 'G')
190:                                    && (this .frontv
191:                                            .indexOf(local.charAt(n + 2)) >= 0)) { // DGE DGI DGY -> J 
192:                                code.append('J');
193:                                n += 2;
194:                            } else {
195:                                code.append('T');
196:                            }
197:                            break;
198:                        case 'G': // GH silent at end or before consonant
199:                            if (isLastChar(wdsz, n + 1)
200:                                    && isNextChar(local, n, 'H')) {
201:                                break;
202:                            }
203:                            if (!isLastChar(wdsz, n + 1)
204:                                    && isNextChar(local, n, 'H')
205:                                    && !isVowel(local, n + 2)) {
206:                                break;
207:                            }
208:                            if ((n > 0)
209:                                    && (regionMatch(local, n, "GN") || regionMatch(
210:                                            local, n, "GNED"))) {
211:                                break; // silent G
212:                            }
213:                            if (isPreviousChar(local, n, 'G')) {
214:                                hard = true;
215:                            } else {
216:                                hard = false;
217:                            }
218:                            if (!isLastChar(wdsz, n)
219:                                    && (this .frontv
220:                                            .indexOf(local.charAt(n + 1)) >= 0)
221:                                    && (!hard)) {
222:                                code.append('J');
223:                            } else {
224:                                code.append('K');
225:                            }
226:                            break;
227:                        case 'H':
228:                            if (isLastChar(wdsz, n)) {
229:                                break; // terminal H
230:                            }
231:                            if ((n > 0)
232:                                    && (this .varson
233:                                            .indexOf(local.charAt(n - 1)) >= 0)) {
234:                                break;
235:                            }
236:                            if (isVowel(local, n + 1)) {
237:                                code.append('H'); // Hvowel
238:                            }
239:                            break;
240:                        case 'F':
241:                        case 'J':
242:                        case 'L':
243:                        case 'M':
244:                        case 'N':
245:                        case 'R':
246:                            code.append(symb);
247:                            break;
248:                        case 'K':
249:                            if (n > 0) { // not initial
250:                                if (!isPreviousChar(local, n, 'C')) {
251:                                    code.append(symb);
252:                                }
253:                            } else {
254:                                code.append(symb); // initial K
255:                            }
256:                            break;
257:                        case 'P':
258:                            if (isNextChar(local, n, 'H')) {
259:                                // PH -> F
260:                                code.append('F');
261:                            } else {
262:                                code.append(symb);
263:                            }
264:                            break;
265:                        case 'Q':
266:                            code.append('K');
267:                            break;
268:                        case 'S':
269:                            if (regionMatch(local, n, "SH")
270:                                    || regionMatch(local, n, "SIO")
271:                                    || regionMatch(local, n, "SIA")) {
272:                                code.append('X');
273:                            } else {
274:                                code.append('S');
275:                            }
276:                            break;
277:                        case 'T':
278:                            if (regionMatch(local, n, "TIA")
279:                                    || regionMatch(local, n, "TIO")) {
280:                                code.append('X');
281:                                break;
282:                            }
283:                            if (regionMatch(local, n, "TCH")) {
284:                                // Silent if in "TCH"
285:                                break;
286:                            }
287:                            // substitute numeral 0 for TH (resembles theta after all)
288:                            if (regionMatch(local, n, "TH")) {
289:                                code.append('0');
290:                            } else {
291:                                code.append('T');
292:                            }
293:                            break;
294:                        case 'V':
295:                            code.append('F');
296:                            break;
297:                        case 'W':
298:                        case 'Y': // silent if not followed by vowel
299:                            if (!isLastChar(wdsz, n) && isVowel(local, n + 1)) {
300:                                code.append(symb);
301:                            }
302:                            break;
303:                        case 'X':
304:                            code.append('K');
305:                            code.append('S');
306:                            break;
307:                        case 'Z':
308:                            code.append('S');
309:                            break;
310:                        } // end switch
311:                        n++;
312:                    } // end else from symb != 'C'
313:                    if (code.length() > this .getMaxCodeLen()) {
314:                        code.setLength(this .getMaxCodeLen());
315:                    }
316:                }
317:                return code.toString();
318:            }
319:
320:            private boolean isVowel(StringBuffer string, int index) {
321:                return (this .vowels.indexOf(string.charAt(index)) >= 0);
322:            }
323:
324:            private boolean isPreviousChar(StringBuffer string, int index,
325:                    char c) {
326:                boolean matches = false;
327:                if (index > 0 && index < string.length()) {
328:                    matches = string.charAt(index - 1) == c;
329:                }
330:                return matches;
331:            }
332:
333:            private boolean isNextChar(StringBuffer string, int index, char c) {
334:                boolean matches = false;
335:                if (index >= 0 && index < string.length() - 1) {
336:                    matches = string.charAt(index + 1) == c;
337:                }
338:                return matches;
339:            }
340:
341:            private boolean regionMatch(StringBuffer string, int index,
342:                    String test) {
343:                boolean matches = false;
344:                if (index >= 0 && (index + test.length() - 1) < string.length()) {
345:                    String substring = string.substring(index, index
346:                            + test.length());
347:                    matches = substring.equals(test);
348:                }
349:                return matches;
350:            }
351:
352:            private boolean isLastChar(int wdsz, int n) {
353:                return n + 1 == wdsz;
354:            }
355:
356:            /**
357:             * Encodes an Object using the metaphone algorithm.  This method
358:             * is provided in order to satisfy the requirements of the
359:             * Encoder interface, and will throw an EncoderException if the
360:             * supplied object is not of type java.lang.String.
361:             *
362:             * @param pObject Object to encode
363:             * @return An object (or type java.lang.String) containing the 
364:             *         metaphone code which corresponds to the String supplied.
365:             * @throws EncoderException if the parameter supplied is not
366:             *                          of type java.lang.String
367:             */
368:            public Object encode(Object pObject) throws EncoderException {
369:                if (!(pObject instanceof  java.lang.String)) {
370:                    throw new EncoderException(
371:                            "Parameter supplied to Metaphone encode is not of type java.lang.String");
372:                }
373:                return metaphone((String) pObject);
374:            }
375:
376:            /**
377:             * Encodes a String using the Metaphone algorithm. 
378:             *
379:             * @param pString String object to encode
380:             * @return The metaphone code corresponding to the String supplied
381:             */
382:            public String encode(String pString) {
383:                return metaphone(pString);
384:            }
385:
386:            /**
387:             * Tests is the metaphones of two strings are identical.
388:             *
389:             * @param str1 First of two strings to compare
390:             * @param str2 Second of two strings to compare
391:             * @return true if the metaphones of these strings are identical, 
392:             *         false otherwise.
393:             */
394:            public boolean isMetaphoneEqual(String str1, String str2) {
395:                return metaphone(str1).equals(metaphone(str2));
396:            }
397:
398:            /**
399:             * Returns the maxCodeLen.
400:             * @return int
401:             */
402:            public int getMaxCodeLen() {
403:                return this .maxCodeLen;
404:            }
405:
406:            /**
407:             * Sets the maxCodeLen.
408:             * @param maxCodeLen The maxCodeLen to set
409:             */
410:            public void setMaxCodeLen(int maxCodeLen) {
411:                this.maxCodeLen = maxCodeLen;
412:            }
413:
414:        }
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