org.apache.commons.codec.language

Class Soundex

java.lang.Object

org.apache.commons.codec.language.Soundex

All Implemented Interfaces:

Encoder, StringEncoder

public class Soundex
extends Object
implements 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 maxLength field is not actually used.

Field Summary

Fields

Modifier and Type	Field and Description
static char	SILENT_MARKER The marker character used to indicate a silent (ignored) character.
static Soundex	US_ENGLISH An instance of Soundex using the US_ENGLISH_MAPPING mapping.
static Soundex	US_ENGLISH_GENEALOGY An instance of Soundex using the mapping as per the Genealogy site: http://www.genealogy.com/articles/research/00000060.html
static String	US_ENGLISH_MAPPING_STRING This is a default mapping of the 26 letters used in US English.
static Soundex	US_ENGLISH_SIMPLIFIED An instance of Soundex using the Simplified Soundex mapping, as described here: http://west-penwith.org.uk/misc/soundex.htm

Constructor Summary

Constructors

Constructor and Description
Soundex() Creates an instance using US_ENGLISH_MAPPING
Soundex(char[] mapping) Creates a soundex instance using the given mapping.
Soundex(String mapping) Creates a refined soundex instance using a custom mapping.
Soundex(String mapping, boolean specialCaseHW) Creates a refined soundex instance using a custom mapping.

Method Summary

Modifier and Type	Method and Description
int	difference(String s1, String s2) Encodes the Strings and returns the number of characters in the two encoded Strings that are the same.
Object	encode(Object obj) Encodes an Object using the soundex algorithm.
String	encode(String str) Encodes a String using the soundex algorithm.
String	soundex(String str) Retrieves the Soundex code for a given String object.

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

SILENT_MARKER

public static final char SILENT_MARKER

The marker character used to indicate a silent (ignored) character. These are ignored except when they appear as the first character.

Note: the US_ENGLISH_MAPPING_STRING does not use this mechanism because changing it might break existing code. Mappings that don't contain a silent marker code are treated as though H and W are silent.

To override this, use the Soundex(String, boolean) constructor.

Since:

1.11

See Also:

Constant Field Values

US_ENGLISH

public static final Soundex US_ENGLISH

An instance of Soundex using the US_ENGLISH_MAPPING mapping. This treats H and W as silent letters. Apart from when they appear as the first letter, they are ignored. They don't act as separators between duplicate codes.

See Also:

US_ENGLISH_MAPPING, US_ENGLISH_MAPPING_STRING

US_ENGLISH_GENEALOGY

public static final Soundex US_ENGLISH_GENEALOGY

An instance of Soundex using the mapping as per the Genealogy site: http://www.genealogy.com/articles/research/00000060.html

This treats vowels (AEIOUY), H and W as silent letters. Such letters are ignored (after the first) and do not act as separators when dropping duplicate codes.

The codes for consonants are otherwise the same as for US_ENGLISH_MAPPING_STRING and US_ENGLISH_SIMPLIFIED

Since:

1.11

US_ENGLISH_MAPPING_STRING

public static final String US_ENGLISH_MAPPING_STRING

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, but treat as a separator when it occurs between consonants with the same code.

(This constant is provided as both an implementation convenience and to allow Javadoc to pick up the value for the constant values page.)

Note that letters H and W are treated specially. They are ignored (after the first letter) and don't act as separators between consonants with the same code.

See Also:

US_ENGLISH_MAPPING, Constant Field Values

US_ENGLISH_SIMPLIFIED

public static final Soundex US_ENGLISH_SIMPLIFIED

An instance of Soundex using the Simplified Soundex mapping, as described here: http://west-penwith.org.uk/misc/soundex.htm

This treats H and W the same as vowels (AEIOUY). Such letters aren't encoded (after the first), but they do act as separators when dropping duplicate codes. The mapping is otherwise the same as for US_ENGLISH

Since:

1.11

Constructor Detail

Soundex

public Soundex()

Creates an instance using US_ENGLISH_MAPPING

See Also:

Soundex(char[]), US_ENGLISH_MAPPING

Soundex

public Soundex(char[] 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

If the mapping contains an instance of SILENT_MARKER then H and W are not given special treatment

Parameters:

mapping - Mapping array to use when finding the corresponding code for a given character

Soundex

public Soundex(String 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.

If the mapping contains an instance of SILENT_MARKER then H and W are not given special treatment

Parameters:

mapping - Mapping string to use when finding the corresponding code for a given character

Since:

1.4

Soundex

public Soundex(String mapping,
               boolean specialCaseHW)

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.

Parameters:

mapping - Mapping string to use when finding the corresponding code for a given character

specialCaseHW - if true, then

Since:

1.11

Method Detail

difference

public int difference(String s1,
                      String s2)
               throws EncoderException

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.

Parameters:

s1 - A String that will be encoded and compared.

s2 - A String that will be encoded and compared.

Returns:

The number of characters in the two encoded Strings that are the same from 0 to 4.

Throws:

EncoderException - if an error occurs encoding one of the strings

Since:

1.3

See Also:

SoundexUtils.difference(StringEncoder,String,String), MS T-SQL DIFFERENCE

encode

public Object encode(Object obj)
              throws EncoderException

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.

Specified by:

encode in interface Encoder

Parameters:

obj - Object to encode

Returns:

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

IllegalArgumentException - if a character is not mapped

encode

public String encode(String str)

Encodes a String using the soundex algorithm.

Specified by:

encode in interface StringEncoder

Parameters:

str - A String object to encode

Returns:

A Soundex code corresponding to the String supplied

Throws:

IllegalArgumentException - if a character is not mapped

soundex

public String soundex(String str)

Retrieves the Soundex code for a given String object.

Parameters:

str - String to encode using the Soundex algorithm

Returns:

A soundex code for the String supplied

Throws:

IllegalArgumentException - if a character is not mapped