org.apache.commons.codec.language.Soundex Maven / Gradle / Ivy
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* 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 Soundex value. Soundex is an encoding used to relate similar names, but can also be used as a
* general purpose scheme to find word with similar phonemes.
*
* This class is thread-safe.
* Although not strictly immutable, the {@link #maxLength} field is not actually used.
*
* @version $Id: Soundex.java 1429868 2013-01-07 16:08:05Z ggregory $
*/
public class Soundex implements StringEncoder {
/**
* This is a default mapping of the 26 letters used in US English. A value of 0 for a letter position
* means do not encode.
*
* (This constant is provided as both an implementation convenience and to allow Javadoc to pick
* up the value for the constant values page.)
*
*
* @see #US_ENGLISH_MAPPING
*/
public static final String US_ENGLISH_MAPPING_STRING = "01230120022455012623010202";
/**
* This is a default mapping of the 26 letters used in US English. A value of 0 for a letter position
* means do not encode.
*
* @see Soundex#Soundex(char[])
*/
private static final char[] US_ENGLISH_MAPPING = US_ENGLISH_MAPPING_STRING.toCharArray();
/**
* An instance of Soundex using the US_ENGLISH_MAPPING mapping.
*
* @see #US_ENGLISH_MAPPING
*/
public static final Soundex US_ENGLISH = new Soundex();
/**
* The maximum length of a Soundex code - Soundex codes are only four characters by definition.
*
* @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
*/
@Deprecated
private int maxLength = 4;
/**
* 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 using US_ENGLISH_MAPPING
*
* @see Soundex#Soundex(char[])
* @see Soundex#US_ENGLISH_MAPPING
*/
public Soundex() {
this.soundexMapping = US_ENGLISH_MAPPING;
}
/**
* Creates a soundex instance using the given mapping. This constructor can be used to provide an internationalized
* mapping for a non-Western character set.
*
* 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
*
* @param mapping
* Mapping array to use when finding the corresponding code for a given character
*/
public Soundex(final char[] mapping) {
this.soundexMapping = new char[mapping.length];
System.arraycopy(mapping, 0, this.soundexMapping, 0, mapping.length);
}
/**
* 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 Soundex(final String mapping) {
this.soundexMapping = mapping.toCharArray();
}
/**
* Encodes the Strings and returns the number of characters in the two encoded Strings that are the same. This
* return value ranges from 0 through 4: 0 indicates little or no similarity, and 4 indicates strong similarity or
* identical values.
*
* @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 4.
*
* @see SoundexUtils#difference(StringEncoder,String,String)
* @see MS
* T-SQL DIFFERENCE
*
* @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 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 java.lang.String.
*
* @param obj
* Object to encode
* @return An object (or type java.lang.String) containing the soundex code which corresponds to the String
* supplied.
* @throws EncoderException
* if the parameter supplied is not of type java.lang.String
* @throws IllegalArgumentException
* if a character is not mapped
*/
@Override
public Object encode(final Object obj) throws EncoderException {
if (!(obj instanceof String)) {
throw new EncoderException("Parameter supplied to Soundex encode is not of type java.lang.String");
}
return soundex((String) obj);
}
/**
* Encodes a String using the soundex algorithm.
*
* @param str
* A String object to encode
* @return A Soundex code corresponding to the String supplied
* @throws IllegalArgumentException
* if a character is not mapped
*/
@Override
public String encode(final String str) {
return soundex(str);
}
/**
* Used internally by the SoundEx algorithm.
*
* Consonants from the same code group separated by W or H are treated as one.
*
* @param str
* the cleaned working string to encode (in upper case).
* @param index
* the character position to encode
* @return Mapping code for a particular character
* @throws IllegalArgumentException
* if the character is not mapped
*/
private char getMappingCode(final String str, final int index) {
// map() throws IllegalArgumentException
final char mappedChar = this.map(str.charAt(index));
// HW rule check
if (index > 1 && mappedChar != '0') {
final char hwChar = str.charAt(index - 1);
if ('H' == hwChar || 'W' == hwChar) {
final char preHWChar = str.charAt(index - 2);
final char firstCode = this.map(preHWChar);
if (firstCode == mappedChar || 'H' == preHWChar || 'W' == preHWChar) {
return 0;
}
}
}
return mappedChar;
}
/**
* Returns the maxLength. Standard Soundex
*
* @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
* @return int
*/
@Deprecated
public int getMaxLength() {
return this.maxLength;
}
/**
* Returns the soundex mapping.
*
* @return soundexMapping.
*/
private char[] getSoundexMapping() {
return this.soundexMapping;
}
/**
* Maps the given upper-case character to its Soundex code.
*
* @param ch
* An upper-case character.
* @return A Soundex code.
* @throws IllegalArgumentException
* Thrown if ch is not mapped.
*/
private char map(final char ch) {
final int index = ch - 'A';
if (index < 0 || index >= this.getSoundexMapping().length) {
throw new IllegalArgumentException("The character is not mapped: " + ch);
}
return this.getSoundexMapping()[index];
}
/**
* Sets the maxLength.
*
* @deprecated This feature is not needed since the encoding size must be constant. Will be removed in 2.0.
* @param maxLength
* The maxLength to set
*/
@Deprecated
public void setMaxLength(final int maxLength) {
this.maxLength = maxLength;
}
/**
* Retrieves the Soundex code for a given String object.
*
* @param str
* String to encode using the Soundex algorithm
* @return A soundex code for the String supplied
* @throws IllegalArgumentException
* if a character is not mapped
*/
public String soundex(String str) {
if (str == null) {
return null;
}
str = SoundexUtils.clean(str);
if (str.length() == 0) {
return str;
}
final char out[] = {'0', '0', '0', '0'};
char last, mapped;
int incount = 1, count = 1;
out[0] = str.charAt(0);
// getMappingCode() throws IllegalArgumentException
last = getMappingCode(str, 0);
while (incount < str.length() && count < out.length) {
mapped = getMappingCode(str, incount++);
if (mapped != 0) {
if (mapped != '0' && mapped != last) {
out[count++] = mapped;
}
last = mapped;
}
}
return new String(out);
}
}
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