dragon.nlp.tool

Class PorterStemmer

java.lang.Object

dragon.nlp.tool.PorterStemmer

All Implemented Interfaces:

Lemmatiser

public class PorterStemmer
extends Object
implements Lemmatiser

Porter stemmer

Copyright: Copyright (c) 2005

Company: IST, Drexel University

Version:

1.0

Author:

Davis Zhou

Field Summary

Fields inherited from interface dragon.nlp.tool.Lemmatiser

FIRSTPOS, LASTPOS

Constructor Summary

Constructors

Constructor and Description
PorterStemmer()

Method Summary

Modifier and Type	Method and Description
void	add(char ch) Add a character to the word being stemmed.
void	add(char[] w, int wLen) Adds wLen characters to the word being stemmed contained in a portion of a char[] array.
char[]	getResultBuffer() Returns a reference to a character buffer containing the results of the stemming process.
int	getResultLength() Returns the length of the word resulting from the stemming process.
String	lemmatize(String word) Gets the base form of the word.
String	lemmatize(String word, int POS) Gets the base form of the word
static void	main(String[] args) Test program for demonstrating the Lemmatiser.
void	stem() Stem the word placed into the Lemmatiser buffer through calls to add().
String	stem(String word) Gets the stem of the word.
String	toString() After a word has been stemmed, it can be retrieved by toString(), or a reference to the internal buffer can be retrieved by getResultBuffer and getResultLength (which is generally more efficient.)

Methods inherited from class java.lang.Object

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

Constructor Detail

PorterStemmer

public PorterStemmer()

Method Detail

stem

public String stem(String word)

Description copied from interface: Lemmatiser

Gets the stem of the word. The result of stemming may be different from that of lemmasting. It is up to the implementations.

Specified by:

stem in interface Lemmatiser

Parameters:

word - the word for processing

Returns:

the stem of a word

lemmatize

public String lemmatize(String word)

Description copied from interface: Lemmatiser

Gets the base form of the word.

Specified by:

lemmatize in interface Lemmatiser

Parameters:

word - the word for lemmatising

Returns:

the base form

lemmatize

public String lemmatize(String word,
                        int POS)

Description copied from interface: Lemmatiser

Gets the base form of the word

Specified by:

lemmatize in interface Lemmatiser

Parameters:

word - the word for lemmatising

POS - the part of speech of the word

Returns:

the base form

add

public void add(char ch)

Add a character to the word being stemmed. When you are finished adding characters, you can call stem(void) to stem the word.

add

public void add(char[] w,
                int wLen)

Adds wLen characters to the word being stemmed contained in a portion of a char[] array. This is like repeated calls of add(char ch), but faster.

toString

public String toString()

After a word has been stemmed, it can be retrieved by toString(), or a reference to the internal buffer can be retrieved by getResultBuffer and getResultLength (which is generally more efficient.)

Overrides:

toString in class Object

getResultLength

public int getResultLength()

Returns the length of the word resulting from the stemming process.

getResultBuffer

public char[] getResultBuffer()

Returns a reference to a character buffer containing the results of the stemming process. You also need to consult getResultLength() to determine the length of the result.

stem

public void stem()

Stem the word placed into the Lemmatiser buffer through calls to add(). Returns true if the stemming process resulted in a word different from the input. You can retrieve the result with getResultLength()/getResultBuffer() or toString().

main

public static void main(String[] args)

Test program for demonstrating the Lemmatiser. It reads text from a a list of files, stems each word, and writes the result to standard output. Note that the word stemmed is expected to be in lower case: forcing lower case must be done outside the Lemmatiser class. Usage: Lemmatiser file-name file-name ...