org.apache.lucene.analysis.shingle
Class ShingleFilter

java.lang.Object
  extended by org.apache.lucene.analysis.TokenStream
      extended by org.apache.lucene.analysis.TokenFilter
          extended by org.apache.lucene.analysis.shingle.ShingleFilter

public class ShingleFilter
extends TokenFilter

A ShingleFilter constructs shingles (token n-grams) from a token stream. In other words, it creates combinations of tokens as a single token.

For example, the sentence "please divide this sentence into shingles" might be tokenized into shingles "please divide", "divide this", "this sentence", "sentence into", and "into shingles".

This filter handles position increments > 1 by inserting filler tokens (tokens with termtext "_"). It does not handle a position increment of 0.


Field Summary
static int DEFAULT_MAX_SHINGLE_SIZE
          default maximum shingle size is 2.
static char[] FILLER_TOKEN
          filler token for when positionIncrement is more than 1
static java.lang.String TOKEN_SEPARATOR
          The string to use when joining adjacent tokens to form a shingle
 
Fields inherited from class org.apache.lucene.analysis.TokenFilter
input
 
Constructor Summary
ShingleFilter(TokenStream input)
          Construct a ShingleFilter with default shingle size.
ShingleFilter(TokenStream input, int maxShingleSize)
          Constructs a ShingleFilter with the specified single size from the TokenStream input
ShingleFilter(TokenStream input, java.lang.String tokenType)
          Construct a ShingleFilter with the specified token type for shingle tokens.
 
Method Summary
 Token next(Token reusableToken)
           
 void setMaxShingleSize(int maxShingleSize)
          Set the max shingle size (default: 2)
 void setOutputUnigrams(boolean outputUnigrams)
          Shall the output stream contain the input tokens (unigrams) as well as shingles? (default: true.)
 void setTokenType(java.lang.String tokenType)
          Set the type of the shingle tokens produced by this filter.
 
Methods inherited from class org.apache.lucene.analysis.TokenFilter
close, reset
 
Methods inherited from class org.apache.lucene.analysis.TokenStream
next
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

FILLER_TOKEN

public static final char[] FILLER_TOKEN
filler token for when positionIncrement is more than 1


DEFAULT_MAX_SHINGLE_SIZE

public static final int DEFAULT_MAX_SHINGLE_SIZE
default maximum shingle size is 2.

See Also:
Constant Field Values

TOKEN_SEPARATOR

public static final java.lang.String TOKEN_SEPARATOR
The string to use when joining adjacent tokens to form a shingle

See Also:
Constant Field Values
Constructor Detail

ShingleFilter

public ShingleFilter(TokenStream input,
                     int maxShingleSize)
Constructs a ShingleFilter with the specified single size from the TokenStream input

Parameters:
input - input stream
maxShingleSize - maximum shingle size produced by the filter.

ShingleFilter

public ShingleFilter(TokenStream input)
Construct a ShingleFilter with default shingle size.

Parameters:
input - input stream

ShingleFilter

public ShingleFilter(TokenStream input,
                     java.lang.String tokenType)
Construct a ShingleFilter with the specified token type for shingle tokens.

Parameters:
input - input stream
tokenType - token type for shingle tokens
Method Detail

setTokenType

public void setTokenType(java.lang.String tokenType)
Set the type of the shingle tokens produced by this filter. (default: "shingle")

Parameters:
tokenType - token tokenType

setOutputUnigrams

public void setOutputUnigrams(boolean outputUnigrams)
Shall the output stream contain the input tokens (unigrams) as well as shingles? (default: true.)

Parameters:
outputUnigrams - Whether or not the output stream shall contain the input tokens (unigrams)

setMaxShingleSize

public void setMaxShingleSize(int maxShingleSize)
Set the max shingle size (default: 2)

Parameters:
maxShingleSize - max size of output shingles

next

public Token next(Token reusableToken)
           throws java.io.IOException
Overrides:
next in class TokenStream
Throws:
java.io.IOException


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