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java.lang.Object org.apache.lucene.util.AttributeSource org.apache.lucene.analysis.TokenStream org.apache.lucene.analysis.Tokenizer org.apache.lucene.analysis.ngram.NGramTokenizer
public class NGramTokenizer
Tokenizes the input into n-grams of the given size(s).
Nested Class Summary |
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Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource |
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AttributeSource.AttributeFactory, AttributeSource.State |
Field Summary | |
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static int |
DEFAULT_MAX_NGRAM_SIZE
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static int |
DEFAULT_MIN_NGRAM_SIZE
|
Fields inherited from class org.apache.lucene.analysis.Tokenizer |
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input |
Constructor Summary | |
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NGramTokenizer(AttributeSource.AttributeFactory factory,
Reader input,
int minGram,
int maxGram)
Creates NGramTokenizer with given min and max n-grams. |
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NGramTokenizer(AttributeSource source,
Reader input,
int minGram,
int maxGram)
Creates NGramTokenizer with given min and max n-grams. |
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NGramTokenizer(Reader input)
Creates NGramTokenizer with default min and max n-grams. |
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NGramTokenizer(Reader input,
int minGram,
int maxGram)
Creates NGramTokenizer with given min and max n-grams. |
Method Summary | |
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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. |
Token |
next()
Deprecated. Will be removed in Lucene 3.0. This method is final, as it should not be overridden. Delegates to the backwards compatibility layer. |
Token |
next(Token reusableToken)
Deprecated. Will be removed in Lucene 3.0. This method is final, as it should not be overridden. Delegates to the backwards compatibility layer. |
void |
reset()
Resets this stream to the beginning. |
void |
reset(Reader input)
Expert: Reset the tokenizer to a new reader. |
Methods inherited from class org.apache.lucene.analysis.Tokenizer |
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close, correctOffset |
Methods inherited from class org.apache.lucene.analysis.TokenStream |
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getOnlyUseNewAPI, setOnlyUseNewAPI |
Methods inherited from class org.apache.lucene.util.AttributeSource |
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addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, restoreState, toString |
Methods inherited from class java.lang.Object |
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clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
Field Detail |
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public static final int DEFAULT_MIN_NGRAM_SIZE
public static final int DEFAULT_MAX_NGRAM_SIZE
Constructor Detail |
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public NGramTokenizer(Reader input, int minGram, int maxGram)
input
- Reader
holding the input to be tokenizedminGram
- the smallest n-gram to generatemaxGram
- the largest n-gram to generatepublic NGramTokenizer(AttributeSource source, Reader input, int minGram, int maxGram)
source
- AttributeSource
to useinput
- Reader
holding the input to be tokenizedminGram
- the smallest n-gram to generatemaxGram
- the largest n-gram to generatepublic NGramTokenizer(AttributeSource.AttributeFactory factory, Reader input, int minGram, int maxGram)
factory
- AttributeSource.AttributeFactory
to useinput
- Reader
holding the input to be tokenizedminGram
- the smallest n-gram to generatemaxGram
- the largest n-gram to generatepublic NGramTokenizer(Reader input)
input
- Reader
holding the input to be tokenizedMethod Detail |
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public final boolean incrementToken() throws IOException
incrementToken
in class TokenStream
Note that this method will be defined abstract in Lucene 3.0.
IOException
public final void end()
TokenStream
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.
end
in class TokenStream
public final Token next(Token reusableToken) throws IOException
TokenStream
This implicitly defines a "contract" between consumers (callers of this method) and producers (implementations of this method that are the source for tokens):
Token
before calling this method again.Token.clear()
before setting the fields in
it and returning itToken
after it
has been returned: the caller may arbitrarily change it. If the producer
needs to hold onto the Token
for subsequent calls, it must clone()
it before storing it. Note that a TokenFilter
is considered a
consumer.
next
in class TokenStream
reusableToken
- a Token
that may or may not be used to return;
this parameter should never be null (the callee is not required to
check for null before using it, but it is a good idea to assert that
it is not null.)
Token
in the stream or null if end-of-stream was hit
IOException
public final Token next() throws IOException
TokenStream
Token
in the stream, or null at EOS.
next
in class TokenStream
IOException
public void reset(Reader input) throws IOException
Tokenizer
reset
in class Tokenizer
IOException
public void reset() throws IOException
TokenStream
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()
).
reset
in class TokenStream
IOException
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