org.apache.lucene.analysis.ngram
Class EdgeNGramTokenFilter

java.lang.Object
  org.apache.lucene.util.AttributeSource
      org.apache.lucene.analysis.TokenStream
          org.apache.lucene.analysis.TokenFilter
              org.apache.lucene.analysis.ngram.EdgeNGramTokenFilter

All Implemented Interfaces:

Closeable

public final class EdgeNGramTokenFilter
extends TokenFilter

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

This TokenFilter create n-grams from the beginning edge or ending edge of a input token.

Nested Class Summary

static class

EdgeNGramTokenFilter.Side Specifies which side of the input the n-gram should be generated from

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

AttributeSource.AttributeFactory, AttributeSource.State

Field Summary

static int	DEFAULT_MAX_GRAM_SIZE
static int	DEFAULT_MIN_GRAM_SIZE
static EdgeNGramTokenFilter.Side	DEFAULT_SIDE

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

input

Constructor Summary

EdgeNGramTokenFilter(TokenStream input, EdgeNGramTokenFilter.Side side, int minGram, int maxGram)
Creates EdgeNGramTokenFilter that can generate n-grams in the sizes of the given range

EdgeNGramTokenFilter(TokenStream input, String sideLabel, int minGram, int maxGram)
Creates EdgeNGramTokenFilter that can generate n-grams in the sizes of the given range

Method Summary

boolean	incrementToken() Consumers (i.e., IndexWriter) use this method to advance the stream to the next token.
void	reset() Reset the filter as well as the input TokenStream.

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

close, end

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_SIDE

public static final EdgeNGramTokenFilter.Side DEFAULT_SIDE

DEFAULT_MAX_GRAM_SIZE

public static final int DEFAULT_MAX_GRAM_SIZE

See Also:

Constant Field Values

DEFAULT_MIN_GRAM_SIZE

public static final int DEFAULT_MIN_GRAM_SIZE

See Also:

Constant Field Values

Constructor Detail

EdgeNGramTokenFilter

public EdgeNGramTokenFilter(TokenStream input,
                            EdgeNGramTokenFilter.Side side,
                            int minGram,
                            int maxGram)

Creates EdgeNGramTokenFilter that can generate n-grams in the sizes of the given range

Parameters:

input - TokenStream holding the input to be tokenized

side - the EdgeNGramTokenFilter.Side from which to chop off an n-gram

minGram - the smallest n-gram to generate

maxGram - the largest n-gram to generate

EdgeNGramTokenFilter

public EdgeNGramTokenFilter(TokenStream input,
                            String sideLabel,
                            int minGram,
                            int maxGram)

Creates EdgeNGramTokenFilter that can generate n-grams in the sizes of the given range

Parameters:

input - TokenStream holding the input to be tokenized

sideLabel - the name of the EdgeNGramTokenFilter.Side from which to chop off an n-gram

minGram - the smallest n-gram to generate

maxGram - the largest n-gram to generate

Method Detail

incrementToken

public final boolean incrementToken()
                             throws IOException

Description copied from class: TokenStream

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 AttributeSource.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 AttributeSource.addAttribute(Class) and AttributeSource.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 TokenStream.incrementToken().

Specified by:

incrementToken in class TokenStream

Returns:

false for end of stream; true otherwise

Throws:

IOException

reset

public void reset()
           throws IOException

Description copied from class: TokenFilter

Reset the filter as well as the input TokenStream.

Overrides:

reset in class TokenFilter

Throws:

IOException