org.apache.lucene.analysis
Class PorterStemFilter

java.lang.Object
  extended by org.apache.lucene.analysis.TokenStream
      extended by org.apache.lucene.analysis.TokenFilter
          extended by org.apache.lucene.analysis.PorterStemFilter

public final class PorterStemFilter
extends TokenFilter

Transforms the token stream as per the Porter stemming algorithm. Note: the input to the stemming filter must already be in lower case, so you will need to use LowerCaseFilter or LowerCaseTokenizer farther down the Tokenizer chain in order for this to work properly!

To use this filter with other analyzers, you'll want to write an Analyzer class that sets up the TokenStream chain as you want it. To use this with LowerCaseTokenizer, for example, you'd write an analyzer like this:

    class MyAnalyzer extends Analyzer {
      public final TokenStream tokenStream(String fieldName, Reader reader) {
        return new PorterStemFilter(new LowerCaseTokenizer(reader));
      }
    }
    


Field Summary
 
Fields inherited from class org.apache.lucene.analysis.TokenFilter
input
 
Constructor Summary
PorterStemFilter(TokenStream in)
           
 
Method Summary
 Token next(Token result)
          Returns the next token in the stream, or null at EOS.
 
Methods inherited from class org.apache.lucene.analysis.TokenFilter
close
 
Methods inherited from class org.apache.lucene.analysis.TokenStream
next, reset
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

PorterStemFilter

public PorterStemFilter(TokenStream in)
Method Detail

next

public final Token next(Token result)
                 throws IOException
Description copied from class: TokenStream
Returns the next token in the stream, or null at EOS. When possible, the input Token should be used as the returned Token (this gives fastest tokenization performance), but this is not required and a new Token may be returned. Callers may re-use a single Token instance for successive calls to this method.

This implicitly defines a "contract" between consumers (callers of this method) and producers (implementations of this method that are the source for tokens):

Note that a TokenFilter is considered a consumer.

Overrides:
next in class TokenStream
Parameters:
result - a Token that may or may not be used to return
Returns:
next token in the stream or null if end-of-stream was hit
Throws:
IOException


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