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/*
 * 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 org.apache.commons.codec.language;

import org.apache.commons.codec.EncoderException;
import org.apache.commons.codec.StringEncoder;

/**
 * Encodes a string into a Soundex value. Soundex is an encoding used to relate similar names, but can also be used as a
 * general purpose scheme to find word with similar phonemes.
 *
 * This class is thread-safe.
 * Although not strictly immutable, the {@link #maxLength} field is not actually used.
 *
 * @version $Id$
 */
public class Soundex implements StringEncoder {

    /**
     * The marker character used to indicate a silent (ignored) character.
     * These are ignored except when they appear as the first character.
     * 

* Note: the {@link #US_ENGLISH_MAPPING_STRING} does not use this mechanism * because changing it might break existing code. Mappings that don't contain * a silent marker code are treated as though H and W are silent. *

* To override this, use the {@link #Soundex(String, boolean)} constructor. * @since 1.11 */ public static final char SILENT_MARKER = '-'; /** * This is a default mapping of the 26 letters used in US English. A value of 0 for a letter position * means do not encode, but treat as a separator when it occurs between consonants with the same code. *

* (This constant is provided as both an implementation convenience and to allow Javadoc to pick * up the value for the constant values page.) *

* Note that letters H and W are treated specially. * They are ignored (after the first letter) and don't act as separators * between consonants with the same code. * @see #US_ENGLISH_MAPPING */ // ABCDEFGHIJKLMNOPQRSTUVWXYZ public static final String US_ENGLISH_MAPPING_STRING = "01230120022455012623010202"; /** * This is a default mapping of the 26 letters used in US English. A value of 0 for a letter position * means do not encode. * * @see Soundex#Soundex(char[]) */ private static final char[] US_ENGLISH_MAPPING = US_ENGLISH_MAPPING_STRING.toCharArray(); /** * An instance of Soundex using the US_ENGLISH_MAPPING mapping. * This treats H and W as silent letters. * Apart from when they appear as the first letter, they are ignored. * They don't act as separators between duplicate codes. * * @see #US_ENGLISH_MAPPING * @see #US_ENGLISH_MAPPING_STRING */ public static final Soundex US_ENGLISH = new Soundex(); /** * An instance of Soundex using the Simplified Soundex mapping, as described here: * http://west-penwith.org.uk/misc/soundex.htm *

* This treats H and W the same as vowels (AEIOUY). * Such letters aren't encoded (after the first), but they do * act as separators when dropping duplicate codes. * The mapping is otherwise the same as for {@link #US_ENGLISH} *

* @since 1.11 */ public static final Soundex US_ENGLISH_SIMPLIFIED = new Soundex(US_ENGLISH_MAPPING_STRING, false); /** * An instance of Soundex using the mapping as per the Genealogy site: * http://www.genealogy.com/articles/research/00000060.html *

* This treats vowels (AEIOUY), H and W as silent letters. * Such letters are ignored (after the first) and do not * act as separators when dropping duplicate codes. *

* The codes for consonants are otherwise the same as for * {@link #US_ENGLISH_MAPPING_STRING} and {@link #US_ENGLISH_SIMPLIFIED} * * @since 1.11 */ public static final Soundex US_ENGLISH_GENEALOGY = new Soundex("-123-12--22455-12623-1-2-2"); // ABCDEFGHIJKLMNOPQRSTUVWXYZ /** * The maximum length of a Soundex code - Soundex codes are only four characters by definition. * * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0. */ @Deprecated private int maxLength = 4; /** * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each * letter is mapped. This implementation contains a default map for US_ENGLISH */ private final char[] soundexMapping; /** * Should H and W be treated specially? *

* In versions of the code prior to 1.11, * the code always treated H and W as silent (ignored) letters. * If this field is false, H and W are no longer special-cased. */ private final boolean specialCaseHW; /** * Creates an instance using US_ENGLISH_MAPPING * * @see Soundex#Soundex(char[]) * @see Soundex#US_ENGLISH_MAPPING */ public Soundex() { this.soundexMapping = US_ENGLISH_MAPPING; this.specialCaseHW = true; } /** * Creates a soundex instance using the given mapping. This constructor can be used to provide an internationalized * mapping for a non-Western character set. * * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each * letter is mapped. This implementation contains a default map for US_ENGLISH *

* If the mapping contains an instance of {@link #SILENT_MARKER} then H and W are not given special treatment * * @param mapping * Mapping array to use when finding the corresponding code for a given character */ public Soundex(final char[] mapping) { this.soundexMapping = new char[mapping.length]; System.arraycopy(mapping, 0, this.soundexMapping, 0, mapping.length); this.specialCaseHW = !hasMarker(this.soundexMapping); } private boolean hasMarker(final char[] mapping) { for(final char ch : mapping) { if (ch == SILENT_MARKER) { return true; } } return false; } /** * Creates a refined soundex instance using a custom mapping. This constructor can be used to customize the mapping, * and/or possibly provide an internationalized mapping for a non-Western character set. *

* If the mapping contains an instance of {@link #SILENT_MARKER} then H and W are not given special treatment * * @param mapping * Mapping string to use when finding the corresponding code for a given character * @since 1.4 */ public Soundex(final String mapping) { this.soundexMapping = mapping.toCharArray(); this.specialCaseHW = !hasMarker(this.soundexMapping); } /** * Creates a refined soundex instance using a custom mapping. This constructor can be used to customize the mapping, * and/or possibly provide an internationalized mapping for a non-Western character set. * * @param mapping * Mapping string to use when finding the corresponding code for a given character * @param specialCaseHW if true, then * @since 1.11 */ public Soundex(final String mapping, final boolean specialCaseHW) { this.soundexMapping = mapping.toCharArray(); this.specialCaseHW = specialCaseHW; } /** * Encodes the Strings and returns the number of characters in the two encoded Strings that are the same. This * return value ranges from 0 through 4: 0 indicates little or no similarity, and 4 indicates strong similarity or * identical values. * * @param s1 * A String that will be encoded and compared. * @param s2 * A String that will be encoded and compared. * @return The number of characters in the two encoded Strings that are the same from 0 to 4. * * @see SoundexUtils#difference(StringEncoder,String,String) * @see MS * T-SQL DIFFERENCE * * @throws EncoderException * if an error occurs encoding one of the strings * @since 1.3 */ public int difference(final String s1, final String s2) throws EncoderException { return SoundexUtils.difference(this, s1, s2); } /** * Encodes an Object using the soundex 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 obj * Object to encode * @return An object (or type java.lang.String) containing the soundex code which corresponds to the String * supplied. * @throws EncoderException * if the parameter supplied is not of type java.lang.String * @throws IllegalArgumentException * if a character is not mapped */ @Override public Object encode(final Object obj) throws EncoderException { if (!(obj instanceof String)) { throw new EncoderException("Parameter supplied to Soundex encode is not of type java.lang.String"); } return soundex((String) obj); } /** * Encodes a String using the soundex algorithm. * * @param str * A String object to encode * @return A Soundex code corresponding to the String supplied * @throws IllegalArgumentException * if a character is not mapped */ @Override public String encode(final String str) { return soundex(str); } /** * Returns the maxLength. Standard Soundex * * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0. * @return int */ @Deprecated public int getMaxLength() { return this.maxLength; } /** * Maps the given upper-case character to its Soundex code. * * @param ch * An upper-case character. * @return A Soundex code. * @throws IllegalArgumentException * Thrown if ch is not mapped. */ private char map(final char ch) { final int index = ch - 'A'; if (index < 0 || index >= this.soundexMapping.length) { throw new IllegalArgumentException("The character is not mapped: " + ch + " (index=" + index + ")"); } return this.soundexMapping[index]; } /** * Sets the maxLength. * * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0. * @param maxLength * The maxLength to set */ @Deprecated public void setMaxLength(final int maxLength) { this.maxLength = maxLength; } /** * Retrieves the Soundex code for a given String object. * * @param str * String to encode using the Soundex algorithm * @return A soundex code for the String supplied * @throws IllegalArgumentException * if a character is not mapped */ public String soundex(String str) { if (str == null) { return null; } str = SoundexUtils.clean(str); if (str.length() == 0) { return str; } final char out[] = {'0', '0', '0', '0'}; int count = 0; final char first = str.charAt(0); out[count++] = first; char lastDigit = map(first); // previous digit for(int i = 1; i < str.length() && count < out.length ; i++) { final char ch = str.charAt(i); if ((this.specialCaseHW) && (ch == 'H' || ch == 'W')) { // these are ignored completely continue; } final char digit = map(ch); if (digit == SILENT_MARKER) { continue; } if (digit != '0' && digit != lastDigit) { // don't store vowels or repeats out[count++] = digit; } lastDigit = digit; } return new String(out); } }





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