org.apache.lucene.analysis.ngram

Class NGramTokenizer

java.lang.Object

org.apache.lucene.util.AttributeSource

org.apache.lucene.analysis.TokenStream

org.apache.lucene.analysis.Tokenizer

org.apache.lucene.analysis.ngram.NGramTokenizer

All Implemented Interfaces:

Closeable

public final class NGramTokenizer
extends Tokenizer

Tokenizes the input into n-grams of the given size(s).

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource

AttributeSource.AttributeFactory, AttributeSource.State

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_MAX_NGRAM_SIZE
static int	DEFAULT_MIN_NGRAM_SIZE

Fields inherited from class org.apache.lucene.analysis.Tokenizer

input

Constructor Summary

Constructors

Constructor and Description
NGramTokenizer(AttributeSource.AttributeFactory factory, Reader input, int minGram, int maxGram) Creates NGramTokenizer with given min and max n-grams.
NGramTokenizer(AttributeSource source, Reader input, int minGram, int maxGram) Creates NGramTokenizer with given min and max n-grams.
NGramTokenizer(Reader input) Creates NGramTokenizer with default min and max n-grams.
NGramTokenizer(Reader input, int minGram, int maxGram) Creates NGramTokenizer with given min and max n-grams.

Method Summary

Methods

Modifier and Type	Method and Description
void	end() This method is called by the consumer after the last token has been consumed, after TokenStream.incrementToken() returned false (using the new TokenStream API).
boolean	incrementToken() Returns the next token in the stream, or null at EOS.
void	reset() Resets this stream to the beginning.

Methods inherited from class org.apache.lucene.analysis.Tokenizer

close, correctOffset, reset

Methods inherited from class org.apache.lucene.util.AttributeSource

addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, restoreState, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

DEFAULT_MIN_NGRAM_SIZE

public static final int DEFAULT_MIN_NGRAM_SIZE

See Also:

Constant Field Values

DEFAULT_MAX_NGRAM_SIZE

public static final int DEFAULT_MAX_NGRAM_SIZE

See Also:

Constant Field Values

Constructor Detail

NGramTokenizer

public NGramTokenizer(Reader input,
              int minGram,
              int maxGram)

Creates NGramTokenizer with given min and max n-grams.

Parameters:

input - Reader holding the input to be tokenized

minGram - the smallest n-gram to generate

maxGram - the largest n-gram to generate

NGramTokenizer

public NGramTokenizer(AttributeSource source,
              Reader input,
              int minGram,
              int maxGram)

Creates NGramTokenizer with given min and max n-grams.

Parameters:

source - AttributeSource to use

input - Reader holding the input to be tokenized

minGram - the smallest n-gram to generate

maxGram - the largest n-gram to generate

NGramTokenizer

public NGramTokenizer(AttributeSource.AttributeFactory factory,
              Reader input,
              int minGram,
              int maxGram)

Creates NGramTokenizer with given min and max n-grams.

Parameters:

factory - AttributeSource.AttributeFactory to use

input - Reader holding the input to be tokenized

minGram - the smallest n-gram to generate

maxGram - the largest n-gram to generate

NGramTokenizer

public NGramTokenizer(Reader input)

Creates NGramTokenizer with default min and max n-grams.

Parameters:

input - Reader holding the input to be tokenized

Method Detail

incrementToken

public boolean incrementToken()
                       throws IOException

Returns the next token in the stream, or null at EOS.

Specified by:

incrementToken in class TokenStream

Returns:

false for end of stream; true otherwise

Throws:

IOException

end

public void end()

Description copied from class: TokenStream

This method is called by the consumer after the last token has been consumed, after TokenStream.incrementToken() returned false (using the new TokenStream API). Streams implementing the old API should upgrade to use this feature.

This method can be used to perform any end-of-stream operations, such as setting the final offset of a stream. The final offset of a stream might differ from the offset of the last token eg in case one or more whitespaces followed after the last token, but a WhitespaceTokenizer was used.

Overrides:

end in class TokenStream

reset

public void reset()
           throws IOException

Description copied from class: TokenStream

Resets this stream to the beginning. This is an optional operation, so subclasses may or may not implement this method. TokenStream.reset() is not needed for the standard indexing process. However, if the tokens of a TokenStream are intended to be consumed more than once, it is necessary to implement TokenStream.reset(). Note that if your TokenStream caches tokens and feeds them back again after a reset, it is imperative that you clone the tokens when you store them away (on the first pass) as well as when you return them (on future passes after TokenStream.reset()).

Overrides:

reset in class TokenStream

Throws:

IOException