    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017
    018package org.apache.commons.codec.language;
    019
    020import org.apache.commons.codec.EncoderException;
    021import org.apache.commons.codec.StringEncoder;
    022
    023/**
    024 * Encodes a string into a Soundex value. Soundex is an encoding used to relate similar names, but can also be used as a
    025 * general purpose scheme to find word with similar phonemes.
    026 *
    027 * This class is thread-safe.
    028 * Although not strictly immutable, the {@link #maxLength} field is not actually used.
    029 *
    030 * @version $Id$
    031 */
    032public class Soundex implements StringEncoder {
    033
    034    /**
    035     * The marker character used to indicate a silent (ignored) character.
    036     * These are ignored except when they appear as the first character.
    037     * <p>
    038     * Note: the {@link #US_ENGLISH_MAPPING_STRING} does not use this mechanism
    039     * because changing it might break existing code. Mappings that don't contain
    040     * a silent marker code are treated as though H and W are silent.
    041     * <p>
    042     * To override this, use the {@link #Soundex(String, boolean)} constructor.
    043     * @since 1.11
    044     */
    045    public static final char SILENT_MARKER = '-';
    046
    047    /**
    048     * This is a default mapping of the 26 letters used in US English. A value of <code>0</code> for a letter position
    049     * means do not encode, but treat as a separator when it occurs between consonants with the same code.
    050     * <p>
    051     * (This constant is provided as both an implementation convenience and to allow Javadoc to pick
    052     * up the value for the constant values page.)
    053     * <p>
    054     * <b>Note that letters H and W are treated specially.</b>
    055     * They are ignored (after the first letter) and don't act as separators
    056     * between consonants with the same code.
    057     * @see #US_ENGLISH_MAPPING
    058     */
    059    //                                                      ABCDEFGHIJKLMNOPQRSTUVWXYZ
    060    public static final String US_ENGLISH_MAPPING_STRING = "01230120022455012623010202";
    061
    062    /**
    063     * This is a default mapping of the 26 letters used in US English. A value of <code>0</code> for a letter position
    064     * means do not encode.
    065     *
    066     * @see Soundex#Soundex(char[])
    067     */
    068    private static final char[] US_ENGLISH_MAPPING = US_ENGLISH_MAPPING_STRING.toCharArray();
    069
    070    /**
    071     * An instance of Soundex using the US_ENGLISH_MAPPING mapping.
    072     * This treats H and W as silent letters.
    073     * Apart from when they appear as the first letter, they are ignored.
    074     * They don't act as separators between duplicate codes.
    075     *
    076     * @see #US_ENGLISH_MAPPING
    077     * @see #US_ENGLISH_MAPPING_STRING
    078     */
    079    public static final Soundex US_ENGLISH = new Soundex();
    080
    081    /**
    082     * An instance of Soundex using the Simplified Soundex mapping, as described here:
    083     * http://west-penwith.org.uk/misc/soundex.htm
    084     * <p>
    085     * This treats H and W the same as vowels (AEIOUY).
    086     * Such letters aren't encoded (after the first), but they do
    087     * act as separators when dropping duplicate codes.
    088     * The mapping is otherwise the same as for {@link #US_ENGLISH}
    089     * <p>
    090     * @since 1.11
    091     */
    092    public static final Soundex US_ENGLISH_SIMPLIFIED = new Soundex(US_ENGLISH_MAPPING_STRING, false);
    093
    094    /**
    095     * An instance of Soundex using the mapping as per the Genealogy site:
    096     * http://www.genealogy.com/articles/research/00000060.html
    097     * <p>
    098     * This treats vowels (AEIOUY), H and W as silent letters.
    099     * Such letters are ignored (after the first) and do not
    100     * act as separators when dropping duplicate codes.
    101     * <p>
    102     * The codes for consonants are otherwise the same as for
    103     * {@link #US_ENGLISH_MAPPING_STRING} and {@link #US_ENGLISH_SIMPLIFIED}
    104     *
    105     * @since 1.11
    106     */
    107    public static final Soundex US_ENGLISH_GENEALOGY = new Soundex("-123-12--22455-12623-1-2-2");
    108    //                                                              ABCDEFGHIJKLMNOPQRSTUVWXYZ
    109
    110    /**
    111     * The maximum length of a Soundex code - Soundex codes are only four characters by definition.
    112     *
    113     * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
    114     */
    115    @Deprecated
    116    private int maxLength = 4;
    117
    118    /**
    119     * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each
    120     * letter is mapped. This implementation contains a default map for US_ENGLISH
    121     */
    122    private final char[] soundexMapping;
    123
    124    /**
    125     * Should H and W be treated specially?
    126     * <p>
    127     * In versions of the code prior to 1.11,
    128     * the code always treated H and W as silent (ignored) letters.
    129     * If this field is false, H and W are no longer special-cased.
    130     */
    131    private final boolean specialCaseHW;
    132
    133    /**
    134     * Creates an instance using US_ENGLISH_MAPPING
    135     *
    136     * @see Soundex#Soundex(char[])
    137     * @see Soundex#US_ENGLISH_MAPPING
    138     */
    139    public Soundex() {
    140        this.soundexMapping = US_ENGLISH_MAPPING;
    141        this.specialCaseHW = true;
    142    }
    143
    144    /**
    145     * Creates a soundex instance using the given mapping. This constructor can be used to provide an internationalized
    146     * mapping for a non-Western character set.
    147     *
    148     * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each
    149     * letter is mapped. This implementation contains a default map for US_ENGLISH
    150     * <p>
    151     * If the mapping contains an instance of {@link #SILENT_MARKER} then H and W are not given special treatment
    152     *
    153     * @param mapping
    154     *                  Mapping array to use when finding the corresponding code for a given character
    155     */
    156    public Soundex(final char[] mapping) {
    157        this.soundexMapping = new char[mapping.length];
    158        System.arraycopy(mapping, 0, this.soundexMapping, 0, mapping.length);
    159        this.specialCaseHW = !hasMarker(this.soundexMapping);
    160    }
    161
    162    private boolean hasMarker(final char[] mapping) {
    163        for(final char ch : mapping) {
    164            if (ch == SILENT_MARKER) {
    165                return true;
    166            }
    167        }
    168        return false;
    169    }
    170
    171    /**
    172     * Creates a refined soundex instance using a custom mapping. This constructor can be used to customize the mapping,
    173     * and/or possibly provide an internationalized mapping for a non-Western character set.
    174     * <p>
    175     * If the mapping contains an instance of {@link #SILENT_MARKER} then H and W are not given special treatment
    176     *
    177     * @param mapping
    178     *            Mapping string to use when finding the corresponding code for a given character
    179     * @since 1.4
    180     */
    181    public Soundex(final String mapping) {
    182        this.soundexMapping = mapping.toCharArray();
    183        this.specialCaseHW = !hasMarker(this.soundexMapping);
    184    }
    185
    186    /**
    187     * Creates a refined soundex instance using a custom mapping. This constructor can be used to customize the mapping,
    188     * and/or possibly provide an internationalized mapping for a non-Western character set.
    189     *
    190     * @param mapping
    191     *            Mapping string to use when finding the corresponding code for a given character
    192     * @param specialCaseHW if true, then
    193     * @since 1.11
    194     */
    195    public Soundex(final String mapping, final boolean specialCaseHW) {
    196        this.soundexMapping = mapping.toCharArray();
    197        this.specialCaseHW = specialCaseHW;
    198    }
    199
    200    /**
    201     * Encodes the Strings and returns the number of characters in the two encoded Strings that are the same. This
    202     * return value ranges from 0 through 4: 0 indicates little or no similarity, and 4 indicates strong similarity or
    203     * identical values.
    204     *
    205     * @param s1
    206     *                  A String that will be encoded and compared.
    207     * @param s2
    208     *                  A String that will be encoded and compared.
    209     * @return The number of characters in the two encoded Strings that are the same from 0 to 4.
    210     *
    211     * @see SoundexUtils#difference(StringEncoder,String,String)
    212     * @see <a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/tsqlref/ts_de-dz_8co5.asp"> MS
    213     *          T-SQL DIFFERENCE </a>
    214     *
    215     * @throws EncoderException
    216     *                  if an error occurs encoding one of the strings
    217     * @since 1.3
    218     */
    219    public int difference(final String s1, final String s2) throws EncoderException {
    220        return SoundexUtils.difference(this, s1, s2);
    221    }
    222
    223    /**
    224     * Encodes an Object using the soundex algorithm. This method is provided in order to satisfy the requirements of
    225     * the Encoder interface, and will throw an EncoderException if the supplied object is not of type java.lang.String.
    226     *
    227     * @param obj
    228     *                  Object to encode
    229     * @return An object (or type java.lang.String) containing the soundex code which corresponds to the String
    230     *             supplied.
    231     * @throws EncoderException
    232     *                  if the parameter supplied is not of type java.lang.String
    233     * @throws IllegalArgumentException
    234     *                  if a character is not mapped
    235     */
    236    @Override
    237    public Object encode(final Object obj) throws EncoderException {
    238        if (!(obj instanceof String)) {
    239            throw new EncoderException("Parameter supplied to Soundex encode is not of type java.lang.String");
    240        }
    241        return soundex((String) obj);
    242    }
    243
    244    /**
    245     * Encodes a String using the soundex algorithm.
    246     *
    247     * @param str
    248     *                  A String object to encode
    249     * @return A Soundex code corresponding to the String supplied
    250     * @throws IllegalArgumentException
    251     *                  if a character is not mapped
    252     */
    253    @Override
    254    public String encode(final String str) {
    255        return soundex(str);
    256    }
    257
    258    /**
    259     * Returns the maxLength. Standard Soundex
    260     *
    261     * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
    262     * @return int
    263     */
    264    @Deprecated
    265    public int getMaxLength() {
    266        return this.maxLength;
    267    }
    268
    269    /**
    270     * Maps the given upper-case character to its Soundex code.
    271     *
    272     * @param ch
    273     *                  An upper-case character.
    274     * @return A Soundex code.
    275     * @throws IllegalArgumentException
    276     *                  Thrown if <code>ch</code> is not mapped.
    277     */
    278    private char map(final char ch) {
    279        final int index = ch - 'A';
    280        if (index < 0 || index >= this.soundexMapping.length) {
    281            throw new IllegalArgumentException("The character is not mapped: " + ch + " (index=" + index + ")");
    282        }
    283        return this.soundexMapping[index];
    284    }
    285
    286    /**
    287     * Sets the maxLength.
    288     *
    289     * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
    290     * @param maxLength
    291     *                  The maxLength to set
    292     */
    293    @Deprecated
    294    public void setMaxLength(final int maxLength) {
    295        this.maxLength = maxLength;
    296    }
    297
    298    /**
    299     * Retrieves the Soundex code for a given String object.
    300     *
    301     * @param str
    302     *                  String to encode using the Soundex algorithm
    303     * @return A soundex code for the String supplied
    304     * @throws IllegalArgumentException
    305     *                  if a character is not mapped
    306     */
    307    public String soundex(String str) {
    308        if (str == null) {
    309            return null;
    310        }
    311        str = SoundexUtils.clean(str);
    312        if (str.length() == 0) {
    313            return str;
    314        }
    315        final char out[] = {'0', '0', '0', '0'};
    316        int count = 0;
    317        final char first = str.charAt(0);
    318        out[count++] = first;
    319        char lastDigit = map(first); // previous digit
    320        for(int i = 1; i < str.length() && count < out.length ; i++) {
    321            final char ch = str.charAt(i);
    322            if ((this.specialCaseHW) && (ch == 'H' || ch == 'W')) { // these are ignored completely
    323                continue;
    324            }
    325            final char digit = map(ch);
    326            if (digit == SILENT_MARKER) {
    327                continue;
    328            }
    329            if (digit != '0' && digit != lastDigit) { // don't store vowels or repeats
    330                out[count++] = digit;
    331            }
    332            lastDigit = digit;
    333        }
    334        return new String(out);
    335    }
    336
    337}