org.apache.lucene.analysis.shingle

## Class ShingleFilter

- java.lang.Object
- - org.apache.lucene.util.AttributeSource
  - - org.apache.lucene.analysis.TokenStream
    - - org.apache.lucene.analysis.TokenFilter
      - - org.apache.lucene.analysis.shingle.ShingleFilter

- All Implemented Interfaces:
    Closeable, AutoCloseable

      public final 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.

- - ### Nested Class Summary

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

      `AttributeSource.State`

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static String` | `DEFAULT_FILLER_TOKEN` filler token for when positionIncrement is more than 1
    `static int` | `DEFAULT_MAX_SHINGLE_SIZE` default maximum shingle size is 2.
    `static int` | `DEFAULT_MIN_SHINGLE_SIZE` default minimum shingle size is 2.
    `static String` | `DEFAULT_TOKEN_SEPARATOR` The default string to use when joining adjacent tokens to form a shingle
    `static String` | `DEFAULT_TOKEN_TYPE` default token type attribute value is "shingle"

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

      `input`

    - ### Fields inherited from class org.apache.lucene.analysis.TokenStream

      `DEFAULT_TOKEN_ATTRIBUTE_FACTORY`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `ShingleFilter(TokenStream input)` Construct a ShingleFilter with default shingle size: 2.
    `ShingleFilter(TokenStream input, int maxShingleSize)` Constructs a ShingleFilter with the specified shingle size from the `TokenStream` `input`
    `ShingleFilter(TokenStream input, int minShingleSize, int maxShingleSize)` Constructs a ShingleFilter with the specified shingle size from the `TokenStream` `input`
    `ShingleFilter(TokenStream input, String tokenType)` Construct a ShingleFilter with the specified token type for shingle tokens and the default shingle size: 2

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `end()`
    `boolean` | `incrementToken()`
    `void` | `reset()`
    `void` | `setFillerToken(String fillerToken)` Sets the string to insert for each position at which there is no token (i.e., when position increment is greater than one).
    `void` | `setMaxShingleSize(int maxShingleSize)` Set the max shingle size (default: 2)
    `void` | `setMinShingleSize(int minShingleSize)` Set the min shingle size (default: 2).
    `void` | `setOutputUnigrams(boolean outputUnigrams)` Shall the output stream contain the input tokens (unigrams) as well as shingles? (default: true.)
    `void` | `setOutputUnigramsIfNoShingles(boolean outputUnigramsIfNoShingles)` Shall we override the behavior of outputUnigrams==false for those times when no shingles are available (because there are fewer than minShingleSize tokens in the input stream)? (default: false.)
    `void` | `setTokenSeparator(String tokenSeparator)` Sets the string to use when joining adjacent tokens to form a shingle
    `void` | `setTokenType(String tokenType)` Set the type of the shingle tokens produced by this filter.

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

      `close`

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

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

    - ### Methods inherited from class java.lang.Object

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

- - ### Field Detail

    - #### DEFAULT_FILLER_TOKEN

          public static final String DEFAULT_FILLER_TOKEN

      filler token for when positionIncrement is more than 1
      See Also:
        Constant Field Values

    - #### DEFAULT_MAX_SHINGLE_SIZE

          public static final int DEFAULT_MAX_SHINGLE_SIZE

      default maximum shingle size is 2.
      See Also:
        Constant Field Values

    - #### DEFAULT_MIN_SHINGLE_SIZE

          public static final int DEFAULT_MIN_SHINGLE_SIZE

      default minimum shingle size is 2.
      See Also:
        Constant Field Values

    - #### DEFAULT_TOKEN_TYPE

          public static final String DEFAULT_TOKEN_TYPE

      default token type attribute value is "shingle"
      See Also:
        Constant Field Values

    - #### DEFAULT_TOKEN_SEPARATOR

          public static final String DEFAULT_TOKEN_SEPARATOR

      The default string to use when joining adjacent tokens to form a shingle
      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### ShingleFilter

          public ShingleFilter(TokenStream input,
                               int minShingleSize,
                               int maxShingleSize)

      Constructs a ShingleFilter with the specified shingle size from the `TokenStream` `input`
      Parameters:
        `input` - input stream
        `minShingleSize` - minimum shingle size produced by the filter.
        `maxShingleSize` - maximum shingle size produced by the filter.

    - #### ShingleFilter

          public ShingleFilter(TokenStream input,
                               int maxShingleSize)

      Constructs a ShingleFilter with the specified shingle 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: 2.
      Parameters:
        `input` - input stream

    - #### ShingleFilter

          public ShingleFilter(TokenStream input,
                               String tokenType)

      Construct a ShingleFilter with the specified token type for shingle tokens and the default shingle size: 2
      Parameters:
        `input` - input stream
        `tokenType` - token type for shingle tokens

  - ### Method Detail

    - #### setTokenType

          public void setTokenType(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)

    - #### setOutputUnigramsIfNoShingles

          public void setOutputUnigramsIfNoShingles(boolean outputUnigramsIfNoShingles)

      Shall we override the behavior of outputUnigrams==false for those times when no shingles are available (because there are fewer than minShingleSize tokens in the input stream)? (default: false.)

      Note that if outputUnigrams==true, then unigrams are always output, regardless of whether any shingles are available.

      Parameters:
        `outputUnigramsIfNoShingles` - Whether or not to output a single unigram when no shingles are available.

    - #### setMaxShingleSize

          public void setMaxShingleSize(int maxShingleSize)

      Set the max shingle size (default: 2)
      Parameters:
        `maxShingleSize` - max size of output shingles

    - #### setMinShingleSize

          public void setMinShingleSize(int minShingleSize)

      Set the min shingle size (default: 2).

      This method requires that the passed in minShingleSize is not greater than maxShingleSize, so make sure that maxShingleSize is set before calling this method.

      The unigram output option is independent of the min shingle size.

      Parameters:
        `minShingleSize` - min size of output shingles

    - #### setTokenSeparator

          public void setTokenSeparator(String tokenSeparator)

      Sets the string to use when joining adjacent tokens to form a shingle
      Parameters:
        `tokenSeparator` - used to separate input stream tokens in output shingles

    - #### setFillerToken

          public void setFillerToken(String fillerToken)

      Sets the string to insert for each position at which there is no token (i.e., when position increment is greater than one).
      Parameters:
        `fillerToken` - string to insert at each position where there is no token

    - #### incrementToken

          public boolean incrementToken()
                                 throws IOException

      Specified by:
        `incrementToken` in class `TokenStream`
      Throws:
        `IOException`

    - #### end

          public void end()
                   throws IOException

      Overrides:
        `end` in class `TokenFilter`
      Throws:
        `IOException`

    - #### reset

          public void reset()
                     throws IOException

      Overrides:
        `reset` in class `TokenFilter`
      Throws:
        `IOException`

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