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 java.util.Locale; import org.apache.commons.codec.EncoderException; import org.apache.commons.codec.StringEncoder; /** * <p> * Encodes a string into a Cologne Phonetic value. * </p> * <p> * Implements the <a href="http://de.wikipedia.org/wiki/K%C3%B6lner_Phonetik">Kölner Phonetik</a> (Cologne Phonetic) * algorithm issued by Hans Joachim Postel in 1969. * </p> * * <p> * The <i>Kölner Phonetik</i> is a phonetic algorithm which is optimized for the German language. It is related to the * well-known soundex algorithm. * </p> * * <h2>Algorithm</h2> * * <ul> * * <li> * <h3>Step 1:</h3> * After preprocessing (conversion to upper case, transcription of <a * href="http://en.wikipedia.org/wiki/Germanic_umlaut">germanic umlauts</a>, removal of non alphabetical characters) the * letters of the supplied text are replaced by their phonetic code according to the following table. * <table border="1"> * <tbody> * <tr> * <th>Letter</th> * <th>Context</th> * <th align="center">Code</th> * </tr> * <tr> * <td>A, E, I, J, O, U, Y</td> * <td></td> * <td align="center">0</td> * </tr> * <tr> * * <td>H</td> * <td></td> * <td align="center">-</td> * </tr> * <tr> * <td>B</td> * <td></td> * <td rowspan="2" align="center">1</td> * </tr> * <tr> * <td>P</td> * <td>not before H</td> * * </tr> * <tr> * <td>D, T</td> * <td>not before C, S, Z</td> * <td align="center">2</td> * </tr> * <tr> * <td>F, V, W</td> * <td></td> * <td rowspan="2" align="center">3</td> * </tr> * <tr> * * <td>P</td> * <td>before H</td> * </tr> * <tr> * <td>G, K, Q</td> * <td></td> * <td rowspan="3" align="center">4</td> * </tr> * <tr> * <td rowspan="2">C</td> * <td>at onset before A, H, K, L, O, Q, R, U, X</td> * * </tr> * <tr> * <td>before A, H, K, O, Q, U, X except after S, Z</td> * </tr> * <tr> * <td>X</td> * <td>not after C, K, Q</td> * <td align="center">48</td> * </tr> * <tr> * <td>L</td> * <td></td> * * <td align="center">5</td> * </tr> * <tr> * <td>M, N</td> * <td></td> * <td align="center">6</td> * </tr> * <tr> * <td>R</td> * <td></td> * <td align="center">7</td> * </tr> * * <tr> * <td>S, Z</td> * <td></td> * <td rowspan="6" align="center">8</td> * </tr> * <tr> * <td rowspan="3">C</td> * <td>after S, Z</td> * </tr> * <tr> * <td>at onset except before A, H, K, L, O, Q, R, U, X</td> * </tr> * * <tr> * <td>not before A, H, K, O, Q, U, X</td> * </tr> * <tr> * <td>D, T</td> * <td>before C, S, Z</td> * </tr> * <tr> * <td>X</td> * <td>after C, K, Q</td> * </tr> * </tbody> * </table> * <p> * <small><i>(Source: <a href= "http://de.wikipedia.org/wiki/K%C3%B6lner_Phonetik#Buchstabencodes" >Wikipedia (de): * Kölner Phonetik -- Buchstabencodes</a>)</i></small> * </p> * * <h4>Example:</h4> * * {@code "M}ü{@code ller-L}ü{@code denscheidt" => "MULLERLUDENSCHEIDT" => "6005507500206880022"} * * </li> * * <li> * <h3>Step 2:</h3> * Collapse of all multiple consecutive code digits. * <h4>Example:</h4> * {@code "6005507500206880022" => "6050750206802"}</li> * * <li> * <h3>Step 3:</h3> * Removal of all codes "0" except at the beginning. This means that two or more identical consecutive digits can occur * if they occur after removing the "0" digits. * * <h4>Example:</h4> * {@code "6050750206802" => "65752682"}</li> * * </ul> * * @see <a href="http://de.wikipedia.org/wiki/K%C3%B6lner_Phonetik">Wikipedia (de): Kölner Phonetik (in German)</a> * @author Apache Software Foundation * @since 1.5 */ public class ColognePhonetic implements StringEncoder { private abstract class CologneBuffer { protected final char[] data; protected int length = 0; public CologneBuffer(char[] data) { this.data = data; this.length = data.length; } public CologneBuffer(int buffSize) { this.data = new char[buffSize]; this.length = 0; } protected abstract char[] copyData(int start, final int length); public int length() { return length; } @Override public String toString() { return new String(copyData(0, length)); } } private class CologneOutputBuffer extends CologneBuffer { public CologneOutputBuffer(int buffSize) { super(buffSize); } public void addRight(char chr) { data[length] = chr; length++; } @Override protected char[] copyData(int start, final int length) { char[] newData = new char[length]; System.arraycopy(data, start, newData, 0, length); return newData; } } private class CologneInputBuffer extends CologneBuffer { public CologneInputBuffer(char[] data) { super(data); } public void addLeft(char ch) { length++; data[getNextPos()] = ch; } @Override protected char[] copyData(int start, final int length) { char[] newData = new char[length]; System.arraycopy(data, data.length - this.length + start, newData, 0, length); return newData; } public char getNextChar() { return data[getNextPos()]; } protected int getNextPos() { return data.length - length; } public char removeNext() { char ch = getNextChar(); length--; return ch; } } /** * Maps some Germanic characters to plain for internal processing. The following characters are mapped: * <ul> * <li>capital a, umlaut mark</li> * <li>capital u, umlaut mark</li> * <li>capital o, umlaut mark</li> * <li>small sharp s, German</li> * </ul> */ private static final char[][] PREPROCESS_MAP = new char[][] { { '\u00C4', 'A' }, // capital a, umlaut mark { '\u00DC', 'U' }, // capital u, umlaut mark { '\u00D6', 'O' }, // capital o, umlaut mark { '\u00DF', 'S' } // small sharp s, German }; /* * Returns whether the array contains the key, or not. */ private static boolean arrayContains(char[] arr, char key) { for (char element : arr) { if (element == key) { return true; } } return false; } /** * <p> * Implements the <i>Kölner Phonetik</i> algorithm. * </p> * <p> * In contrast to the initial description of the algorithm, this implementation does the encoding in one pass. * </p> * * @param text * @return the corresponding encoding according to the <i>Kölner Phonetik</i> algorithm */ public String colognePhonetic(String text) { if (text == null) { return null; } text = preprocess(text); CologneOutputBuffer output = new CologneOutputBuffer(text.length() * 2); CologneInputBuffer input = new CologneInputBuffer(text.toCharArray()); char nextChar; char lastChar = '-'; char lastCode = '/'; char code; char chr; int rightLength = input.length(); while (rightLength > 0) { chr = input.removeNext(); if ((rightLength = input.length()) > 0) { nextChar = input.getNextChar(); } else { nextChar = '-'; } if (arrayContains(new char[] { 'A', 'E', 'I', 'J', 'O', 'U', 'Y' }, chr)) { code = '0'; } else if (chr == 'H' || chr < 'A' || chr > 'Z') { if (lastCode == '/') { continue; } code = '-'; } else if (chr == 'B' || (chr == 'P' && nextChar != 'H')) { code = '1'; } else if ((chr == 'D' || chr == 'T') && !arrayContains(new char[] { 'S', 'C', 'Z' }, nextChar)) { code = '2'; } else if (arrayContains(new char[] { 'W', 'F', 'P', 'V' }, chr)) { code = '3'; } else if (arrayContains(new char[] { 'G', 'K', 'Q' }, chr)) { code = '4'; } else if (chr == 'X' && !arrayContains(new char[] { 'C', 'K', 'Q' }, lastChar)) { code = '4'; input.addLeft('S'); rightLength++; } else if (chr == 'S' || chr == 'Z') { code = '8'; } else if (chr == 'C') { if (lastCode == '/') { if (arrayContains(new char[] { 'A', 'H', 'K', 'L', 'O', 'Q', 'R', 'U', 'X' }, nextChar)) { code = '4'; } else { code = '8'; } } else { if (arrayContains(new char[] { 'S', 'Z' }, lastChar) || !arrayContains(new char[] { 'A', 'H', 'O', 'U', 'K', 'Q', 'X' }, nextChar)) { code = '8'; } else { code = '4'; } } } else if (arrayContains(new char[] { 'T', 'D', 'X' }, chr)) { code = '8'; } else if (chr == 'R') { code = '7'; } else if (chr == 'L') { code = '5'; } else if (chr == 'M' || chr == 'N') { code = '6'; } else { code = chr; } if (code != '-' && (lastCode != code && (code != '0' || lastCode == '/') || code < '0' || code > '8')) { output.addRight(code); } lastChar = chr; lastCode = code; } return output.toString(); } @Override public Object encode(Object object) throws EncoderException { if (!(object instanceof String)) { throw new EncoderException( "This method's parameter was expected to be of the type " + String.class.getName() + ". But actually it was of the type " + object.getClass().getName() + "."); } return encode((String) object); } @Override public String encode(String text) { return colognePhonetic(text); } public boolean isEncodeEqual(String text1, String text2) { return colognePhonetic(text1).equals(colognePhonetic(text2)); } /** * Converts the string to upper case and replaces germanic characters as defined in {@link #PREPROCESS_MAP}. */ private String preprocess(String text) { text = text.toUpperCase(Locale.GERMAN); char[] chrs = text.toCharArray(); for (int index = 0; index < chrs.length; index++) { if (chrs[index] > 'Z') { for (char[] element : PREPROCESS_MAP) { if (chrs[index] == element[0]) { chrs[index] = element[1]; break; } } } } return new String(chrs); } }