Source code

    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: Soundex.java 1429868 2013-01-07 16:08:05Z ggregory $
    031 */
    032public class Soundex implements StringEncoder {
    033
    034    /**
    035     * This is a default mapping of the 26 letters used in US English. A value of <code>0</code> for a letter position
    036     * means do not encode.
    037     * <p>
    038     * (This constant is provided as both an implementation convenience and to allow Javadoc to pick
    039     * up the value for the constant values page.)
    040     * </p>
    041     *
    042     * @see #US_ENGLISH_MAPPING
    043     */
    044    public static final String US_ENGLISH_MAPPING_STRING = "01230120022455012623010202";
    045
    046    /**
    047     * This is a default mapping of the 26 letters used in US English. A value of <code>0</code> for a letter position
    048     * means do not encode.
    049     *
    050     * @see Soundex#Soundex(char[])
    051     */
    052    private static final char[] US_ENGLISH_MAPPING = US_ENGLISH_MAPPING_STRING.toCharArray();
    053
    054    /**
    055     * An instance of Soundex using the US_ENGLISH_MAPPING mapping.
    056     *
    057     * @see #US_ENGLISH_MAPPING
    058     */
    059    public static final Soundex US_ENGLISH = new Soundex();
    060
    061    /**
    062     * The maximum length of a Soundex code - Soundex codes are only four characters by definition.
    063     *
    064     * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
    065     */
    066    @Deprecated
    067    private int maxLength = 4;
    068
    069    /**
    070     * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each
    071     * letter is mapped. This implementation contains a default map for US_ENGLISH
    072     */
    073    private final char[] soundexMapping;
    074
    075    /**
    076     * Creates an instance using US_ENGLISH_MAPPING
    077     *
    078     * @see Soundex#Soundex(char[])
    079     * @see Soundex#US_ENGLISH_MAPPING
    080     */
    081    public Soundex() {
    082        this.soundexMapping = US_ENGLISH_MAPPING;
    083    }
    084
    085    /**
    086     * Creates a soundex instance using the given mapping. This constructor can be used to provide an internationalized
    087     * mapping for a non-Western character set.
    088     *
    089     * Every letter of the alphabet is "mapped" to a numerical value. This char array holds the values to which each
    090     * letter is mapped. This implementation contains a default map for US_ENGLISH
    091     *
    092     * @param mapping
    093     *                  Mapping array to use when finding the corresponding code for a given character
    094     */
    095    public Soundex(final char[] mapping) {
    096        this.soundexMapping = new char[mapping.length];
    097        System.arraycopy(mapping, 0, this.soundexMapping, 0, mapping.length);
    098    }
    099
    100    /**
    101     * Creates a refined soundex instance using a custom mapping. This constructor can be used to customize the mapping,
    102     * and/or possibly provide an internationalized mapping for a non-Western character set.
    103     *
    104     * @param mapping
    105     *            Mapping string to use when finding the corresponding code for a given character
    106     * @since 1.4
    107     */
    108    public Soundex(final String mapping) {
    109        this.soundexMapping = mapping.toCharArray();
    110    }
    111
    112    /**
    113     * Encodes the Strings and returns the number of characters in the two encoded Strings that are the same. This
    114     * return value ranges from 0 through 4: 0 indicates little or no similarity, and 4 indicates strong similarity or
    115     * identical values.
    116     *
    117     * @param s1
    118     *                  A String that will be encoded and compared.
    119     * @param s2
    120     *                  A String that will be encoded and compared.
    121     * @return The number of characters in the two encoded Strings that are the same from 0 to 4.
    122     *
    123     * @see SoundexUtils#difference(StringEncoder,String,String)
    124     * @see <a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/tsqlref/ts_de-dz_8co5.asp"> MS
    125     *          T-SQL DIFFERENCE </a>
    126     *
    127     * @throws EncoderException
    128     *                  if an error occurs encoding one of the strings
    129     * @since 1.3
    130     */
    131    public int difference(final String s1, final String s2) throws EncoderException {
    132        return SoundexUtils.difference(this, s1, s2);
    133    }
    134
    135    /**
    136     * Encodes an Object using the soundex algorithm. This method is provided in order to satisfy the requirements of
    137     * the Encoder interface, and will throw an EncoderException if the supplied object is not of type java.lang.String.
    138     *
    139     * @param obj
    140     *                  Object to encode
    141     * @return An object (or type java.lang.String) containing the soundex code which corresponds to the String
    142     *             supplied.
    143     * @throws EncoderException
    144     *                  if the parameter supplied is not of type java.lang.String
    145     * @throws IllegalArgumentException
    146     *                  if a character is not mapped
    147     */
    148    @Override
    149    public Object encode(final Object obj) throws EncoderException {
    150        if (!(obj instanceof String)) {
    151            throw new EncoderException("Parameter supplied to Soundex encode is not of type java.lang.String");
    152        }
    153        return soundex((String) obj);
    154    }
    155
    156    /**
    157     * Encodes a String using the soundex algorithm.
    158     *
    159     * @param str
    160     *                  A String object to encode
    161     * @return A Soundex code corresponding to the String supplied
    162     * @throws IllegalArgumentException
    163     *                  if a character is not mapped
    164     */
    165    @Override
    166    public String encode(final String str) {
    167        return soundex(str);
    168    }
    169
    170    /**
    171     * Used internally by the SoundEx algorithm.
    172     *
    173     * Consonants from the same code group separated by W or H are treated as one.
    174     *
    175     * @param str
    176     *                  the cleaned working string to encode (in upper case).
    177     * @param index
    178     *                  the character position to encode
    179     * @return Mapping code for a particular character
    180     * @throws IllegalArgumentException
    181     *                  if the character is not mapped
    182     */
    183    private char getMappingCode(final String str, final int index) {
    184        // map() throws IllegalArgumentException
    185        final char mappedChar = this.map(str.charAt(index));
    186        // HW rule check
    187        if (index > 1 && mappedChar != '0') {
    188            final char hwChar = str.charAt(index - 1);
    189            if ('H' == hwChar || 'W' == hwChar) {
    190                final char preHWChar = str.charAt(index - 2);
    191                final char firstCode = this.map(preHWChar);
    192                if (firstCode == mappedChar || 'H' == preHWChar || 'W' == preHWChar) {
    193                    return 0;
    194                }
    195            }
    196        }
    197        return mappedChar;
    198    }
    199
    200    /**
    201     * Returns the maxLength. Standard Soundex
    202     *
    203     * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
    204     * @return int
    205     */
    206    @Deprecated
    207    public int getMaxLength() {
    208        return this.maxLength;
    209    }
    210
    211    /**
    212     * Returns the soundex mapping.
    213     *
    214     * @return soundexMapping.
    215     */
    216    private char[] getSoundexMapping() {
    217        return this.soundexMapping;
    218    }
    219
    220    /**
    221     * Maps the given upper-case character to its Soundex code.
    222     *
    223     * @param ch
    224     *                  An upper-case character.
    225     * @return A Soundex code.
    226     * @throws IllegalArgumentException
    227     *                  Thrown if <code>ch</code> is not mapped.
    228     */
    229    private char map(final char ch) {
    230        final int index = ch - 'A';
    231        if (index < 0 || index >= this.getSoundexMapping().length) {
    232            throw new IllegalArgumentException("The character is not mapped: " + ch);
    233        }
    234        return this.getSoundexMapping()[index];
    235    }
    236
    237    /**
    238     * Sets the maxLength.
    239     *
    240     * @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
    241     * @param maxLength
    242     *                  The maxLength to set
    243     */
    244    @Deprecated
    245    public void setMaxLength(final int maxLength) {
    246        this.maxLength = maxLength;
    247    }
    248
    249    /**
    250     * Retrieves the Soundex code for a given String object.
    251     *
    252     * @param str
    253     *                  String to encode using the Soundex algorithm
    254     * @return A soundex code for the String supplied
    255     * @throws IllegalArgumentException
    256     *                  if a character is not mapped
    257     */
    258    public String soundex(String str) {
    259        if (str == null) {
    260            return null;
    261        }
    262        str = SoundexUtils.clean(str);
    263        if (str.length() == 0) {
    264            return str;
    265        }
    266        final char out[] = {'0', '0', '0', '0'};
    267        char last, mapped;
    268        int incount = 1, count = 1;
    269        out[0] = str.charAt(0);
    270        // getMappingCode() throws IllegalArgumentException
    271        last = getMappingCode(str, 0);
    272        while (incount < str.length() && count < out.length) {
    273            mapped = getMappingCode(str, incount++);
    274            if (mapped != 0) {
    275                if (mapped != '0' && mapped != last) {
    276                    out[count++] = mapped;
    277                }
    278                last = mapped;
    279            }
    280        }
    281        return new String(out);
    282    }
    283
    284}