org.apache.commons.codec.language
Class Nysiis

java.lang.Object
  org.apache.commons.codec.language.Nysiis

All Implemented Interfaces:

Encoder, StringEncoder

public class Nysiis
extends Object
implements StringEncoder

Encodes a string into a NYSIIS value. NYSIIS is an encoding used to relate similar names, but can also be used as a general purpose scheme to find word with similar phonemes.

NYSIIS features an accuracy increase of 2.7% over the traditional Soundex algorithm.

Algorithm description:

 1. Transcode first characters of name
   1a. MAC ->   MCC
   1b. KN  ->   NN
   1c. K   ->   C
   1d. PH  ->   FF
   1e. PF  ->   FF
   1f. SCH ->   SSS
 2. Transcode last characters of name
   2a. EE, IE          ->   Y
   2b. DT,RT,RD,NT,ND  ->   D
 3. First character of key = first character of name
 4. Transcode remaining characters by following these rules, incrementing by one character each time
   4a. EV  ->   AF  else A,E,I,O,U -> A
   4b. Q   ->   G
   4c. Z   ->   S
   4d. M   ->   N
   4e. KN  ->   N   else K -> C
   4f. SCH ->   SSS
   4g. PH  ->   FF
   4h. H   ->   If previous or next is nonvowel, previous
   4i. W   ->   If previous is vowel, previous
   4j. Add current to key if current != last key character
 5. If last character is S, remove it
 6. If last characters are AY, replace with Y
 7. If last character is A, remove it
 8. Collapse all strings of repeated characters
 9. Add original first character of name as first character of key
 

This class is immutable and thread-safe.

Since:

1.7

Version:

$Id: Nysiis.java 1429868 2013-01-07 16:08:05Z ggregory $

See Also:

NYSIIS on Wikipedia, NYSIIS on dropby.com, Soundex

Field Summary

private static char[]	CHARS_A
private static char[]	CHARS_AF
private static char[]	CHARS_C
private static char[]	CHARS_FF
private static char[]	CHARS_G
private static char[]	CHARS_N
private static char[]	CHARS_NN
private static char[]	CHARS_S
private static char[]	CHARS_SSS
private static Pattern	PAT_DT_ETC
private static Pattern	PAT_EE_IE
private static Pattern	PAT_K
private static Pattern	PAT_KN
private static Pattern	PAT_MAC
private static Pattern	PAT_PH_PF
private static Pattern	PAT_SCH
private static char	SPACE
private boolean	strict Indicates the strict mode.
private static int	TRUE_LENGTH

Constructor Summary

Nysiis()
Creates an instance of the Nysiis encoder with strict mode (original form), i.e.

Nysiis(boolean strict)
Create an instance of the Nysiis encoder with the specified strict mode: true: encoded strings have a maximum length of 6 false: encoded strings may have arbitrary length

Method Summary

Object	encode(Object obj) Encodes an Object using the NYSIIS algorithm.
String	encode(String str) Encodes a String using the NYSIIS algorithm.
boolean	isStrict() Indicates the strict mode for this Nysiis encoder.
private static boolean	isVowel(char c) Tests if the given character is a vowel.
String	nysiis(String str) Retrieves the NYSIIS code for a given String object.
private static char[]	transcodeRemaining(char prev, char curr, char next, char aNext) Transcodes the remaining parts of the String.

Methods inherited from class java.lang.Object

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

Field Detail

CHARS_A

private static final char[] CHARS_A

CHARS_AF

private static final char[] CHARS_AF

CHARS_C

private static final char[] CHARS_C

CHARS_FF

private static final char[] CHARS_FF

CHARS_G

private static final char[] CHARS_G

CHARS_N

private static final char[] CHARS_N

CHARS_NN

private static final char[] CHARS_NN

CHARS_S

private static final char[] CHARS_S

CHARS_SSS

private static final char[] CHARS_SSS

PAT_MAC

private static final Pattern PAT_MAC

PAT_KN

private static final Pattern PAT_KN

PAT_K

private static final Pattern PAT_K

PAT_PH_PF

private static final Pattern PAT_PH_PF

PAT_SCH

private static final Pattern PAT_SCH

PAT_EE_IE

private static final Pattern PAT_EE_IE

PAT_DT_ETC

private static final Pattern PAT_DT_ETC

SPACE

private static final char SPACE

See Also:

Constant Field Values

TRUE_LENGTH

private static final int TRUE_LENGTH

See Also:

Constant Field Values

strict

private final boolean strict

Indicates the strict mode.

Constructor Detail

Nysiis

public Nysiis()

Creates an instance of the Nysiis encoder with strict mode (original form), i.e. encoded strings have a maximum length of 6.

Nysiis

public Nysiis(boolean strict)

Create an instance of the Nysiis encoder with the specified strict mode:

• true: encoded strings have a maximum length of 6
• false: encoded strings may have arbitrary length

Parameters:

strict - the strict mode

Method Detail

isVowel

private static boolean isVowel(char c)

Tests if the given character is a vowel.

Parameters:

c - the character to test

Returns:

true if the character is a vowel, false otherwise

transcodeRemaining

private static char[] transcodeRemaining(char prev,
                                         char curr,
                                         char next,
                                         char aNext)

Transcodes the remaining parts of the String. The method operates on a sliding window, looking at 4 characters at a time: [i-1, i, i+1, i+2].

Parameters:

prev - the previous character

curr - the current character

next - the next character

aNext - the after next character

Returns:

a transcoded array of characters, starting from the current position

encode

public Object encode(Object obj)
              throws EncoderException

Encodes an Object using the NYSIIS 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 String.

Specified by:

encode in interface Encoder

Parameters:

obj - Object to encode

Returns:

An object (or a String) containing the NYSIIS code which corresponds to the given String.

Throws:

EncoderException - if the parameter supplied is not of a String

IllegalArgumentException - if a character is not mapped

encode

public String encode(String str)

Encodes a String using the NYSIIS algorithm.

Specified by:

encode in interface StringEncoder

Parameters:

str - A String object to encode

Returns:

A Nysiis code corresponding to the String supplied

Throws:

IllegalArgumentException - if a character is not mapped

isStrict

public boolean isStrict()

Indicates the strict mode for this Nysiis encoder.

Returns:

true if the encoder is configured for strict mode, false otherwise

nysiis

public String nysiis(String str)

Retrieves the NYSIIS code for a given String object.

Parameters:

str - String to encode using the NYSIIS algorithm

Returns:

A NYSIIS code for the String supplied