    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
    018    package org.apache.commons.codec.language;
    019
    020    import org.apache.commons.codec.EncoderException;
    021    import 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     */
    032    public 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    }