    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 Refined Soundex value. A refined soundex code is
    025 * optimized for spell checking words. Soundex method originally developed by
    026 * <CITE>Margaret Odell</CITE> and <CITE>Robert Russell</CITE>.
    027 *
    028 * <p>This class is immutable and thread-safe.</p>
    029 *
    030 */
    031public class RefinedSoundex implements StringEncoder {
    032
    033    /**
    034     * Mapping:
    035     * <pre>
    036     * 0: A E I O U Y H W
    037     * 1: B P
    038     * 2: F V
    039     * 3: C K S
    040     * 4: G J
    041     * 5: Q X Z
    042     * 6: D T
    043     * 7: L
    044     * 8: M N
    045     * 9: R
    046     * </pre>
    047     * @since 1.4
    048     */
    049    //                                                      ABCDEFGHIJKLMNOPQRSTUVWXYZ
    050    public static final String US_ENGLISH_MAPPING_STRING = "01360240043788015936020505";
    051
    052   /**
    053     * RefinedSoundex is *refined* for a number of reasons one being that the
    054     * mappings have been altered. This implementation contains default
    055     * mappings for US English.
    056     */
    057    private static final char[] US_ENGLISH_MAPPING = US_ENGLISH_MAPPING_STRING.toCharArray();
    058
    059    /**
    060     * Every letter of the alphabet is "mapped" to a numerical value. This char
    061     * array holds the values to which each letter is mapped. This
    062     * implementation contains a default map for US_ENGLISH
    063     */
    064    private final char[] soundexMapping;
    065
    066    /**
    067     * This static variable contains an instance of the RefinedSoundex using
    068     * the US_ENGLISH mapping.
    069     */
    070    public static final RefinedSoundex US_ENGLISH = new RefinedSoundex();
    071
    072     /**
    073     * Creates an instance of the RefinedSoundex object using the default US
    074     * English mapping.
    075     */
    076    public RefinedSoundex() {
    077        this.soundexMapping = US_ENGLISH_MAPPING;
    078    }
    079
    080    /**
    081     * Creates a refined soundex instance using a custom mapping. This
    082     * constructor can be used to customize the mapping, and/or possibly
    083     * provide an internationalized mapping for a non-Western character set.
    084     *
    085     * @param mapping
    086     *                  Mapping array to use when finding the corresponding code for
    087     *                  a given character
    088     */
    089    public RefinedSoundex(final char[] mapping) {
    090        this.soundexMapping = new char[mapping.length];
    091        System.arraycopy(mapping, 0, this.soundexMapping, 0, mapping.length);
    092    }
    093
    094    /**
    095     * Creates a refined Soundex instance using a custom mapping. This constructor can be used to customize the mapping,
    096     * and/or possibly provide an internationalized mapping for a non-Western character set.
    097     *
    098     * @param mapping
    099     *            Mapping string to use when finding the corresponding code for a given character
    100     * @since 1.4
    101     */
    102    public RefinedSoundex(final String mapping) {
    103        this.soundexMapping = mapping.toCharArray();
    104    }
    105
    106    /**
    107     * Returns the number of characters in the two encoded Strings that are the
    108     * same. This return value ranges from 0 to the length of the shortest
    109     * encoded String: 0 indicates little or no similarity, and 4 out of 4 (for
    110     * example) indicates strong similarity or identical values. For refined
    111     * Soundex, the return value can be greater than 4.
    112     *
    113     * @param s1
    114     *                  A String that will be encoded and compared.
    115     * @param s2
    116     *                  A String that will be encoded and compared.
    117     * @return The number of characters in the two encoded Strings that are the
    118     *             same from 0 to to the length of the shortest encoded String.
    119     *
    120     * @see SoundexUtils#difference(StringEncoder,String,String)
    121     * @see <a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/tsqlref/ts_de-dz_8co5.asp">
    122     *          MS T-SQL DIFFERENCE</a>
    123     *
    124     * @throws EncoderException
    125     *                  if an error occurs encoding one of the strings
    126     * @since 1.3
    127     */
    128    public int difference(final String s1, final String s2) throws EncoderException {
    129        return SoundexUtils.difference(this, s1, s2);
    130    }
    131
    132    /**
    133     * Encodes an Object using the refined soundex algorithm. This method is
    134     * provided in order to satisfy the requirements of the Encoder interface,
    135     * and will throw an EncoderException if the supplied object is not of type
    136     * java.lang.String.
    137     *
    138     * @param obj
    139     *                  Object to encode
    140     * @return An object (or type java.lang.String) containing the refined
    141     *             soundex code which corresponds to the String supplied.
    142     * @throws EncoderException
    143     *                  if the parameter supplied is not of type java.lang.String
    144     */
    145    @Override
    146    public Object encode(final Object obj) throws EncoderException {
    147        if (!(obj instanceof String)) {
    148            throw new EncoderException("Parameter supplied to RefinedSoundex encode is not of type java.lang.String");
    149        }
    150        return soundex((String) obj);
    151    }
    152
    153    /**
    154     * Encodes a String using the refined soundex algorithm.
    155     *
    156     * @param str
    157     *                  A String object to encode
    158     * @return A Soundex code corresponding to the String supplied
    159     */
    160    @Override
    161    public String encode(final String str) {
    162        return soundex(str);
    163    }
    164
    165    /**
    166     * Returns the mapping code for a given character. The mapping codes are
    167     * maintained in an internal char array named soundexMapping, and the
    168     * default values of these mappings are US English.
    169     *
    170     * @param c
    171     *                  char to get mapping for
    172     * @return A character (really a numeral) to return for the given char
    173     */
    174    char getMappingCode(final char c) {
    175        if (!Character.isLetter(c)) {
    176            return 0;
    177        }
    178        return this.soundexMapping[Character.toUpperCase(c) - 'A'];
    179    }
    180
    181    /**
    182     * Retrieves the Refined Soundex code for a given String object.
    183     *
    184     * @param str
    185     *                  String to encode using the Refined Soundex algorithm
    186     * @return A soundex code for the String supplied
    187     */
    188    public String soundex(String str) {
    189        if (str == null) {
    190            return null;
    191        }
    192        str = SoundexUtils.clean(str);
    193        if (str.length() == 0) {
    194            return str;
    195        }
    196
    197        final StringBuilder sBuf = new StringBuilder();
    198        sBuf.append(str.charAt(0));
    199
    200        char last, current;
    201        last = '*';
    202
    203        for (int i = 0; i < str.length(); i++) {
    204
    205            current = getMappingCode(str.charAt(i));
    206            if (current == last) {
    207                continue;
    208            } else if (current != 0) {
    209                sBuf.append(current);
    210            }
    211
    212            last = current;
    213
    214        }
    215
    216        return sBuf.toString();
    217    }
    218}