Class PorterStemFilter

  • All Implemented Interfaces:
    Closeable, AutoCloseable

    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 {
          protected TokenStreamComponents createComponents(String fieldName) {
            Tokenizer source = new LowerCaseTokenizer(version, reader);
            return new TokenStreamComponents(source, new PorterStemFilter(source));

    Note: This filter is aware of the KeywordAttribute. To prevent certain terms from being passed to the stemmer KeywordAttribute.isKeyword() should be set to true in a previous TokenStream. Note: For including the original term as well as the stemmed version, see KeywordRepeatFilterFactory