RefinedSoundex.java
/*
* 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 Refined Soundex value. A refined soundex code is
* optimized for spell checking words. Soundex method originally developed by
* <CITE>Margaret Odell</CITE> and <CITE>Robert Russell</CITE>.
*
* <p>This class is immutable and thread-safe.</p>
*/
public class RefinedSoundex implements StringEncoder {
/**
* Mapping:
* <pre>
* 0: A E I O U Y H W
* 1: B P
* 2: F V
* 3: C K S
* 4: G J
* 5: Q X Z
* 6: D T
* 7: L
* 8: M N
* 9: R
* </pre>
* @since 1.4
*/
// ABCDEFGHIJKLMNOPQRSTUVWXYZ
public static final String US_ENGLISH_MAPPING_STRING = "01360240043788015936020505";
/**
* RefinedSoundex is *refined* for a number of reasons one being that the
* mappings have been altered. This implementation contains default
* mappings for US English.
*/
private static final char[] US_ENGLISH_MAPPING = US_ENGLISH_MAPPING_STRING.toCharArray();
/**
* This static variable contains an instance of the RefinedSoundex using
* the US_ENGLISH mapping.
*/
public static final RefinedSoundex US_ENGLISH = new RefinedSoundex();
/**
* 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;
/**
* Creates an instance of the RefinedSoundex object using the default US
* English mapping.
*/
public RefinedSoundex() {
this.soundexMapping = US_ENGLISH_MAPPING;
}
/**
* 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 array to use when finding the corresponding code for
* a given character
*/
public RefinedSoundex(final char[] mapping) {
this.soundexMapping = mapping.clone();
}
/**
* 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
* @since 1.4
*/
public RefinedSoundex(final String mapping) {
this.soundexMapping = mapping.toCharArray();
}
/**
* Returns the number of characters in the two encoded Strings that are the
* same. This return value ranges from 0 to the length of the shortest
* encoded String: 0 indicates little or no similarity, and 4 out of 4 (for
* example) indicates strong similarity or identical values. For refined
* Soundex, the return value can be greater than 4.
*
* @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 the length of the shortest encoded String.
*
* @see SoundexUtils#difference(StringEncoder,String,String)
* @see <a href="https://msdn.microsoft.com/library/default.asp?url=/library/en-us/tsqlref/ts_de-dz_8co5.asp">
* MS T-SQL DIFFERENCE</a>
*
* @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 refined 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
* {@link String}.
*
* @param obj
* Object to encode
* @return An object (or type {@link String}) containing the refined
* soundex code which corresponds to the String supplied.
* @throws EncoderException
* if the parameter supplied is not of type {@link String}
*/
@Override
public Object encode(final Object obj) throws EncoderException {
if (!(obj instanceof String)) {
throw new EncoderException("Parameter supplied to RefinedSoundex encode is not of type java.lang.String");
}
return soundex((String) obj);
}
/**
* Encodes a String using the refined soundex algorithm.
*
* @param str
* A String object to encode
* @return A Soundex code corresponding to the String supplied
*/
@Override
public String encode(final String str) {
return soundex(str);
}
/**
* Returns the mapping code for a given character. The mapping codes are
* maintained in an internal char array named soundexMapping, and the
* default values of these mappings are US English.
*
* @param c
* char to get mapping for
* @return A character (really a numeral) to return for the given char
*/
char getMappingCode(final char c) {
if (!Character.isLetter(c)) {
return 0;
}
final int index = Character.toUpperCase(c) - 'A';
if (index < 0 || index >= this.soundexMapping.length) {
return 0;
}
return this.soundexMapping[index];
}
/**
* Retrieves the Refined Soundex code for a given String object.
*
* @param str
* String to encode using the Refined Soundex algorithm
* @return A soundex code for the String supplied
*/
public String soundex(String str) {
if (str == null) {
return null;
}
str = SoundexUtils.clean(str);
if (str.isEmpty()) {
return str;
}
final StringBuilder sBuf = new StringBuilder();
sBuf.append(str.charAt(0));
char last, current;
last = '*';
for (int i = 0; i < str.length(); i++) {
current = getMappingCode(str.charAt(i));
if (current == last) {
continue;
}
if (current != 0) {
sBuf.append(current);
}
last = current;
}
return sBuf.toString();
}
}