Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package net.yacy.cora.language.phonetic; import org.apache.commons.codec.EncoderException; import org.apache.commons.codec.StringEncoder; /** * Encodes a string into a Metaphone value. * <p> * Initial Java implementation by <CITE>William B. Brogden. December, 1997</CITE>. * Permission given by <CITE>wbrogden</CITE> for code to be used anywhere. * </p> * <p> * <CITE>Hanging on the Metaphone</CITE> by <CITE>Lawrence Philips</CITE> in <CITE>Computer Language of Dec. 1990, p * 39.</CITE> * </p> * <p> * Note, that this does not match the algorithm that ships with PHP, or the algorithm * found in the Perl <a href="http://search.cpan.org/~mschwern/Text-Metaphone-1.96/Metaphone.pm">Text:Metaphone-1.96</a>. * They have had undocumented changes from the originally published algorithm. * For more information, see <a href="https://issues.apache.org/jira/browse/CODEC-57">CODEC-57</a>. * </p> * * @author Apache Software Foundation * @version $Id: Metaphone.java 1157192 2011-08-12 17:27:38Z ggregory $ */ public class Metaphone implements StringEncoder { /** * Five values in the English language */ private static final String VOWELS = "AEIOU"; /** * Variable used in Metaphone algorithm */ private static final String FRONTV = "EIY"; /** * Variable used in Metaphone algorithm */ private static final String VARSON = "CSPTG"; /** * The max code length for metaphone is 4 */ private int maxCodeLen = 4; /** * Creates an instance of the Metaphone encoder */ public Metaphone() { super(); } /** * Find the metaphone value of a String. This is similar to the * soundex algorithm, but better at finding similar sounding words. * All input is converted to upper case. * Limitations: Input format is expected to be a single ASCII word * with only characters in the A - Z range, no punctuation or numbers. * * @param txt String to find the metaphone code for * @return A metaphone code corresponding to the String supplied */ public String metaphone(String txt) { boolean hard = false; if ((txt == null) || (txt.isEmpty())) { return ""; } // single character is itself if (txt.length() == 1) { return txt.toUpperCase(java.util.Locale.ENGLISH); } char[] inwd = txt.toUpperCase(java.util.Locale.ENGLISH).toCharArray(); StringBuilder local = new StringBuilder(40); // manipulate StringBuilder code = new StringBuilder(10); // output // handle initial 2 characters exceptions switch (inwd[0]) { case 'K': case 'G': case 'P': /* looking for KN, etc*/ if (inwd[1] == 'N') { local.append(inwd, 1, inwd.length - 1); } else { local.append(inwd); } break; case 'A': /* looking for AE */ if (inwd[1] == 'E') { local.append(inwd, 1, inwd.length - 1); } else { local.append(inwd); } break; case 'W': /* looking for WR or WH */ if (inwd[1] == 'R') { // WR -> R local.append(inwd, 1, inwd.length - 1); break; } if (inwd[1] == 'H') { local.append(inwd, 1, inwd.length - 1); local.setCharAt(0, 'W'); // WH -> W } else { local.append(inwd); } break; case 'X': /* initial X becomes S */ inwd[0] = 'S'; local.append(inwd); break; default: local.append(inwd); } // now local has working string with initials fixed int wdsz = local.length(); int n = 0; while ((code.length() < this.getMaxCodeLen()) && (n < wdsz)) { // max code size of 4 works well char symb = local.charAt(n); // remove duplicate letters except C if ((symb != 'C') && (isPreviousChar(local, n, symb))) { n++; } else { // not dup switch (symb) { case 'A': case 'E': case 'I': case 'O': case 'U': if (n == 0) { code.append(symb); } break; // only use vowel if leading char case 'B': if (isPreviousChar(local, n, 'M') && isLastChar(wdsz, n)) { // B is silent if word ends in MB break; } code.append(symb); break; case 'C': // lots of C special cases /* discard if SCI, SCE or SCY */ if (isPreviousChar(local, n, 'S') && !isLastChar(wdsz, n) && (FRONTV.indexOf(local.charAt(n + 1)) >= 0)) { break; } if (regionMatch(local, n, "CIA")) { // "CIA" -> X code.append('X'); break; } if (!isLastChar(wdsz, n) && (FRONTV.indexOf(local.charAt(n + 1)) >= 0)) { code.append('S'); break; // CI,CE,CY -> S } if (isPreviousChar(local, n, 'S') && isNextChar(local, n, 'H')) { // SCH->sk code.append('K'); break; } if (isNextChar(local, n, 'H')) { // detect CH if ((n == 0) && (wdsz >= 3) && isVowel(local, 2)) { // CH consonant -> K consonant code.append('K'); } else { code.append('X'); // CHvowel -> X } } else { code.append('K'); } break; case 'D': if (!isLastChar(wdsz, n + 1) && isNextChar(local, n, 'G') && (FRONTV.indexOf(local.charAt(n + 2)) >= 0)) { // DGE DGI DGY -> J code.append('J'); n += 2; } else { code.append('T'); } break; case 'G': // GH silent at end or before consonant if (isLastChar(wdsz, n + 1) && isNextChar(local, n, 'H')) { break; } if (!isLastChar(wdsz, n + 1) && isNextChar(local, n, 'H') && !isVowel(local, n + 2)) { break; } if ((n > 0) && (regionMatch(local, n, "GN") || regionMatch(local, n, "GNED"))) { break; // silent G } if (isPreviousChar(local, n, 'G')) { // NOTE: Given that duplicated chars are removed, I don't see how this can ever be true hard = true; } else { hard = false; } if (!isLastChar(wdsz, n) && (FRONTV.indexOf(local.charAt(n + 1)) >= 0) && (!hard)) { code.append('J'); } else { code.append('K'); } break; case 'H': if (isLastChar(wdsz, n)) { break; // terminal H } if ((n > 0) && (VARSON.indexOf(local.charAt(n - 1)) >= 0)) { break; } if (isVowel(local, n + 1)) { code.append('H'); // Hvowel } break; case 'F': case 'J': case 'L': case 'M': case 'N': case 'R': code.append(symb); break; case 'K': if (n > 0) { // not initial if (!isPreviousChar(local, n, 'C')) { code.append(symb); } } else { code.append(symb); // initial K } break; case 'P': if (isNextChar(local, n, 'H')) { // PH -> F code.append('F'); } else { code.append(symb); } break; case 'Q': code.append('K'); break; case 'S': if (regionMatch(local, n, "SH") || regionMatch(local, n, "SIO") || regionMatch(local, n, "SIA")) { code.append('X'); } else { code.append('S'); } break; case 'T': if (regionMatch(local, n, "TIA") || regionMatch(local, n, "TIO")) { code.append('X'); break; } if (regionMatch(local, n, "TCH")) { // Silent if in "TCH" break; } // substitute numeral 0 for TH (resembles theta after all) if (regionMatch(local, n, "TH")) { code.append('0'); } else { code.append('T'); } break; case 'V': code.append('F'); break; case 'W': case 'Y': // silent if not followed by vowel if (!isLastChar(wdsz, n) && isVowel(local, n + 1)) { code.append(symb); } break; case 'X': code.append('K'); code.append('S'); break; case 'Z': code.append('S'); break; } // end switch n++; } // end else from symb != 'C' if (code.length() > this.getMaxCodeLen()) { code.setLength(this.getMaxCodeLen()); } } return code.toString(); } private boolean isVowel(StringBuilder string, int index) { return VOWELS.indexOf(string.charAt(index)) >= 0; } private boolean isPreviousChar(StringBuilder string, int index, char c) { boolean matches = false; if (index > 0 && index < string.length()) { matches = string.charAt(index - 1) == c; } return matches; } private boolean isNextChar(StringBuilder string, int index, char c) { boolean matches = false; if (index >= 0 && index < string.length() - 1) { matches = string.charAt(index + 1) == c; } return matches; } private boolean regionMatch(StringBuilder string, int index, String test) { boolean matches = false; if (index >= 0 && (index + test.length() - 1) < string.length()) { String substring = string.substring(index, index + test.length()); matches = substring.equals(test); } return matches; } private boolean isLastChar(int wdsz, int n) { return n + 1 == wdsz; } /** * Encodes an Object using the metaphone algorithm. This method * is provided in order to satisfy the requirements of the * Encoder interface, and will throw an EncoderException if the * supplied object is not of type java.lang.String. * * @param pObject Object to encode * @return An object (or type java.lang.String) containing the * metaphone code which corresponds to the String supplied. * @throws EncoderException if the parameter supplied is not * of type java.lang.String */ @Override public Object encode(Object pObject) throws EncoderException { if (!(pObject instanceof String)) { throw new EncoderException("Parameter supplied to Metaphone encode is not of type java.lang.String"); } return metaphone((String) pObject); } /** * Encodes a String using the Metaphone algorithm. * * @param pString String object to encode * @return The metaphone code corresponding to the String supplied */ @Override public String encode(String pString) { return metaphone(pString); } /** * Tests is the metaphones of two strings are identical. * * @param str1 First of two strings to compare * @param str2 Second of two strings to compare * @return <code>true</code> if the metaphones of these strings are identical, * <code>false</code> otherwise. */ public boolean isMetaphoneEqual(String str1, String str2) { return metaphone(str1).equals(metaphone(str2)); } /** * Returns the maxCodeLen. * @return int */ public int getMaxCodeLen() { return this.maxCodeLen; } /** * Sets the maxCodeLen. * @param maxCodeLen The maxCodeLen to set */ public void setMaxCodeLen(int maxCodeLen) { this.maxCodeLen = maxCodeLen; } }