Java tutorial
/* * Licensed to Elasticsearch under one or more contributor * license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright * ownership. Elasticsearch 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 org.elasticsearch.index.analysis.phonetic; import org.apache.commons.codec.EncoderException; import org.apache.commons.codec.StringEncoder; import java.util.regex.Pattern; /** * * Taken from commons-codec trunk (unreleased yet) * * Encodes a string into a NYSIIS value. NYSIIS is an encoding used to relate * similar names, but can also be used as a general purpose scheme to find word * with similar phonemes. * * <p> NYSIIS features an accuracy increase of 2.7% over the traditional Soundex * algorithm. </p> * * <p>Algorithm description: * <pre> * 1. Transcode first characters of name * 1a. MAC -> MCC * 1b. KN -> NN * 1c. K -> C * 1d. PH -> FF * 1e. PF -> FF * 1f. SCH -> SSS * 2. Transcode last characters of name * 2a. EE, IE -> Y * 2b. DT,RT,RD,NT,ND -> D * 3. First character of key = first character of name * 4. Transcode remaining characters by following these rules, incrementing by one character each time * 4a. EV -> AF else A,E,I,O,U -> A * 4b. Q -> G * 4c. Z -> S * 4d. M -> N * 4e. KN -> N else K -> C * 4f. SCH -> SSS * 4g. PH -> FF * 4h. H -> If previous or next is nonvowel, previous * 4i. W -> If previous is vowel, previous * 4j. Add current to key if current != last key character * 5. If last character is S, remove it * 6. If last characters are AY, replace with Y * 7. If last character is A, remove it * 8. Collapse all strings of repeated characters * 9. Add original first character of name as first character of key * </pre> * * @see <a href="http://en.wikipedia.org/wiki/NYSIIS">NYSIIS on Wikipedia</a> * @see <a href="http://www.dropby.com/NYSIIS.html">NYSIIS on dropby.com</a> * */ public class Nysiis implements StringEncoder { private static final char[] CHARS_A = new char[] { 'A' }; private static final char[] CHARS_AF = new char[] { 'A', 'F' }; private static final char[] CHARS_C = new char[] { 'C' }; private static final char[] CHARS_FF = new char[] { 'F', 'F' }; private static final char[] CHARS_G = new char[] { 'G' }; private static final char[] CHARS_N = new char[] { 'N' }; private static final char[] CHARS_NN = new char[] { 'N', 'N' }; private static final char[] CHARS_S = new char[] { 'S' }; private static final char[] CHARS_SSS = new char[] { 'S', 'S', 'S' }; private static final Pattern PAT_MAC = Pattern.compile("^MAC"); private static final Pattern PAT_KN = Pattern.compile("^KN"); private static final Pattern PAT_K = Pattern.compile("^K"); private static final Pattern PAT_PH_PF = Pattern.compile("^(PH|PF)"); private static final Pattern PAT_SCH = Pattern.compile("^SCH"); private static final Pattern PAT_EE_IE = Pattern.compile("(EE|IE)$"); private static final Pattern PAT_DT_ETC = Pattern.compile("(DT|RT|RD|NT|ND)$"); private static final char SPACE = ' '; private static final int TRUE_LENGTH = 6; /** * Tests if the given character is a vowel. * * @param c the character to test * @return {@code true} if the character is a vowel, {@code false} otherwise */ private static boolean isVowel(final char c) { return c == 'A' || c == 'E' || c == 'I' || c == 'O' || c == 'U'; } /** * Transcodes the remaining parts of the String. The method operates on a * sliding window, looking at 4 characters at a time: [i-1, i, i+1, i+2]. * * @param prev the previous character * @param curr the current character * @param next the next character * @param aNext the after next character * @return a transcoded array of characters, starting from the current * position */ private static char[] transcodeRemaining(final char prev, final char curr, final char next, final char aNext) { // 1. EV -> AF if (curr == 'E' && next == 'V') { return CHARS_AF; } // A, E, I, O, U -> A if (isVowel(curr)) { return CHARS_A; } // 2. Q -> G, Z -> S, M -> N if (curr == 'Q') { return CHARS_G; } else if (curr == 'Z') { return CHARS_S; } else if (curr == 'M') { return CHARS_N; } // 3. KN -> NN else K -> C if (curr == 'K') { if (next == 'N') { return CHARS_NN; } else { return CHARS_C; } } // 4. SCH -> SSS if (curr == 'S' && next == 'C' && aNext == 'H') { return CHARS_SSS; } // PH -> FF if (curr == 'P' && next == 'H') { return CHARS_FF; } // 5. H -> If previous or next is a non vowel, previous. if (curr == 'H' && (!isVowel(prev) || !isVowel(next))) { return new char[] { prev }; } // 6. W -> If previous is vowel, previous. if (curr == 'W' && isVowel(prev)) { return new char[] { prev }; } return new char[] { curr }; } /** * Indicates the strict mode. */ private final boolean strict; /** * Creates an instance of the {@link Nysiis} encoder with strict mode * (original form), i.e. encoded strings have a maximum length of 6. */ public Nysiis() { this(true); } /** * Create an instance of the {@link Nysiis} encoder with the specified * strict mode: * * <ul> <li>{@code true}: encoded strings have a maximum length of 6</li> <li>{@code false}: * encoded strings may have arbitrary length</li> </ul> * * @param strict the strict mode */ public Nysiis(final boolean strict) { this.strict = strict; } /** * Encodes an Object using the NYSIIS algorithm. This method is provided in * order to satisfy the requirements of the Encoder interface, and will * throw an {@link EncoderException} if the supplied object is not of type * {@link String}. * * @param obj Object to encode * @return An object (or a {@link String}) containing the NYSIIS code which * corresponds to the given String. * @throws EncoderException if the parameter supplied is not of a {@link String} * @throws IllegalArgumentException if a character is not mapped */ @Override public Object encode(Object obj) throws EncoderException { if (!(obj instanceof String)) { throw new EncoderException("Parameter supplied to Nysiis encode is not of type java.lang.String"); } return this.nysiis((String) obj); } /** * Encodes a String using the NYSIIS algorithm. * * @param str A String object to encode * @return A Nysiis code corresponding to the String supplied * @throws IllegalArgumentException if a character is not mapped */ @Override public String encode(String str) { return this.nysiis(str); } /** * Indicates the strict mode for this {@link Nysiis} encoder. * * @return {@code true} if the encoder is configured for strict mode, {@code false} * otherwise */ public boolean isStrict() { return this.strict; } /** * Retrieves the NYSIIS code for a given String object. * * @param str String to encode using the NYSIIS algorithm * @return A NYSIIS code for the String supplied */ public String nysiis(String str) { if (str == null) { return null; } // Use the same clean rules as Soundex str = clean(str); if (str.length() == 0) { return str; } // Translate first characters of name: // MAC -> MCC, KN -> NN, K -> C, PH | PF -> FF, SCH -> SSS str = PAT_MAC.matcher(str).replaceFirst("MCC"); str = PAT_KN.matcher(str).replaceFirst("NN"); str = PAT_K.matcher(str).replaceFirst("C"); str = PAT_PH_PF.matcher(str).replaceFirst("FF"); str = PAT_SCH.matcher(str).replaceFirst("SSS"); // Translate last characters of name: // EE -> Y, IE -> Y, DT | RT | RD | NT | ND -> D str = PAT_EE_IE.matcher(str).replaceFirst("Y"); str = PAT_DT_ETC.matcher(str).replaceFirst("D"); // First character of key = first character of name. StringBuilder key = new StringBuilder(str.length()); key.append(str.charAt(0)); // Transcode remaining characters, incrementing by one character each time final char[] chars = str.toCharArray(); final int len = chars.length; for (int i = 1; i < len; i++) { final char next = i < len - 1 ? chars[i + 1] : SPACE; final char aNext = i < len - 2 ? chars[i + 2] : SPACE; final char[] transcoded = transcodeRemaining(chars[i - 1], chars[i], next, aNext); System.arraycopy(transcoded, 0, chars, i, transcoded.length); // only append the current char to the key if it is different from the last one if (chars[i] != chars[i - 1]) { key.append(chars[i]); } } if (key.length() > 1) { char lastChar = key.charAt(key.length() - 1); // If last character is S, remove it. if (lastChar == 'S') { key.deleteCharAt(key.length() - 1); lastChar = key.charAt(key.length() - 1); } if (key.length() > 2) { final char last2Char = key.charAt(key.length() - 2); // If last characters are AY, replace with Y. if (last2Char == 'A' && lastChar == 'Y') { key.deleteCharAt(key.length() - 2); } } // If last character is A, remove it. if (lastChar == 'A') { key.deleteCharAt(key.length() - 1); } } final String string = key.toString(); return this.isStrict() ? string.substring(0, Math.min(TRUE_LENGTH, string.length())) : string; } static String clean(String str) { if (str == null || str.length() == 0) { return str; } int len = str.length(); char[] chars = new char[len]; int count = 0; for (int i = 0; i < len; i++) { if (Character.isLetter(str.charAt(i))) { chars[count++] = str.charAt(i); } } if (count == len) { return str.toUpperCase(java.util.Locale.ENGLISH); } return new String(chars, 0, count).toUpperCase(java.util.Locale.ENGLISH); } }