PorterStemFilter

extends TokenFilter

java.lang.Object
↳	org.apache.lucene.util.AttributeSource
	↳	org.apache.lucene.analysis.TokenStream
		↳	org.apache.lucene.analysis.TokenFilter
			↳	org.apache.lucene.analysis.PorterStemFilter

Class Overview

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));
      }
    }

Summary

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Inherited Fields

From class org.apache.lucene.analysis.TokenFilter

Public Constructors
	PorterStemFilter(TokenStream in)

Public Methods
final boolean	incrementToken() Consumers (i.e., `IndexWriter`) use this method to advance the stream to the next token.

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Inherited Methods

From class org.apache.lucene.analysis.TokenFilter

From class org.apache.lucene.analysis.TokenStream

From class org.apache.lucene.util.AttributeSource

From class java.lang.Object

From interface java.io.Closeable

Public Constructors

public PorterStemFilter (TokenStream in)

Public Methods

public final boolean incrementToken ()

Consumers (i.e., IndexWriter) use this method to advance the stream to the next token. Implementing classes must implement this method and update the appropriate AttributeImpls with the attributes of the next token.

The producer must make no assumptions about the attributes after the method has been returned: the caller may arbitrarily change it. If the producer needs to preserve the state for subsequent calls, it can use captureState() to create a copy of the current attribute state.

This method is called for every token of a document, so an efficient implementation is crucial for good performance. To avoid calls to addAttribute(Class) and getAttribute(Class), references to all AttributeImpls that this stream uses should be retrieved during instantiation.

To ensure that filters and consumers know which attributes are available, the attributes must be added during instantiation. Filters and consumers are not required to check for availability of attributes in incrementToken().

Returns

false for end of stream; true otherwise

Throws

IOException

Classes