org.apache.lucene.analysis

Class Analyzer

public abstract class Analyzer extends Object

An Analyzer builds TokenStreams, which analyze text. It thus represents a policy for extracting index terms from text.

Typical implementations first build a Tokenizer, which breaks the stream of characters from the Reader into raw Tokens. One or more TokenFilters may then be applied to the output of the Tokenizer.

WARNING: You must override one of the methods defined by this class in your subclass or the Analyzer will enter an infinite loop.

Method Summary
intgetPositionIncrementGap(String fieldName)
Invoked before indexing a Fieldable instance if terms have already been added to that field.
abstract TokenStreamtokenStream(String fieldName, Reader reader)
Creates a TokenStream which tokenizes all the text in the provided Reader.

Method Detail

getPositionIncrementGap

public int getPositionIncrementGap(String fieldName)
Invoked before indexing a Fieldable instance if terms have already been added to that field. This allows custom analyzers to place an automatic position increment gap between Fieldable instances using the same field name. The default value position increment gap is 0. With a 0 position increment gap and the typical default token position increment of 1, all terms in a field, including across Fieldable instances, are in successive positions, allowing exact PhraseQuery matches, for instance, across Fieldable instance boundaries.

Parameters: fieldName Fieldable name being indexed.

Returns: position increment gap, added to the next token emitted from tokenStream

tokenStream

public abstract TokenStream tokenStream(String fieldName, Reader reader)
Creates a TokenStream which tokenizes all the text in the provided Reader. Default implementation forwards to tokenStream(Reader) for compatibility with older version. Override to allow Analyzer to choose strategy based on document and/or field. Must be able to handle null field name for backward compatibility.
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