org.apache.lucene.analysis.snowball: public class: SnowballFilter

org.apache.lucene.analysis.snowball
public class: SnowballFilter [javadoc | source]

java.lang.Object
   org.apache.lucene.analysis.TokenStream
      org.apache.lucene.analysis.TokenFilter
         org.apache.lucene.analysis.snowball.SnowballFilter

A filter that stems words using a Snowball-generated stemmer. Available stemmers are listed in net.sf.snowball.ext . The name of a stemmer is the part of the class name before "Stemmer", e.g., the stemmer in EnglishStemmer is named "English".

Fields inherited from org.apache.lucene.analysis.TokenFilter:
input

Constructor:

Constructor:
public SnowballFilter(TokenStream in, String name) { super(in); try { Class stemClass = Class.forName("net.sf.snowball.ext." + name + "Stemmer"); stemmer = (SnowballProgram) stemClass.newInstance(); // why doesn't the SnowballProgram class have an (abstract?) stem method? stemMethod = stemClass.getMethod("stem", new Class[0]); } catch (Exception e) { throw new RuntimeException(e.toString()); } } Construct the named stemming filter. Parameters: `in` - the input tokens to stem `name` - the name of a stemmer

 public SnowballFilter(TokenStream in,
    String name) {
                        
    super(in);
    try {
      Class stemClass =
        Class.forName("net.sf.snowball.ext." + name + "Stemmer");
      stemmer = (SnowballProgram) stemClass.newInstance();
      // why doesn't the SnowballProgram class have an (abstract?) stem method?
      stemMethod = stemClass.getMethod("stem", new Class[0]);
    } catch (Exception e) {
      throw new RuntimeException(e.toString());
    }
}

Construct the named stemming filter.

Parameters:

in - the input tokens to stem

name - the name of a stemmer

Method from org.apache.lucene.analysis.snowball.SnowballFilter Summary:
next

Methods from org.apache.lucene.analysis.TokenFilter:
close

Methods from org.apache.lucene.analysis.TokenStream:
close, next, next, reset

Methods from java.lang.Object:
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method from org.apache.lucene.analysis.snowball.SnowballFilter Detail:
public final Token next() throws IOException { Token token = input.next(); if (token == null) return null; stemmer.setCurrent(token.termText()); try { stemMethod.invoke(stemmer, EMPTY_ARGS); } catch (Exception e) { throw new RuntimeException(e.toString()); } Token newToken = new Token(stemmer.getCurrent(), token.startOffset(), token.endOffset(), token.type()); newToken.setPositionIncrement(token.getPositionIncrement()); return newToken; } Returns the next input Token, after being stemmed

Method from org.apache.lucene.analysis.snowball.SnowballFilter Detail:

 public final Token next() throws IOException {
    Token token = input.next();
    if (token == null)
      return null;
    stemmer.setCurrent(token.termText());
    try {
      stemMethod.invoke(stemmer, EMPTY_ARGS);
    } catch (Exception e) {
      throw new RuntimeException(e.toString());
    }
    Token newToken = new Token(stemmer.getCurrent(),
                      token.startOffset(), token.endOffset(), token.type());
    newToken.setPositionIncrement(token.getPositionIncrement());
    return newToken;
}

Returns the next input Token, after being stemmed