org.apache.lucene.analysis.miscellaneous

## Class FingerprintFilter

- java.lang.Object
- - org.apache.lucene.util.AttributeSource
  - - org.apache.lucene.analysis.TokenStream
    - - org.apache.lucene.analysis.TokenFilter
      - - org.apache.lucene.analysis.miscellaneous.FingerprintFilter

- All Implemented Interfaces:
    Closeable, AutoCloseable

      public class FingerprintFilter
      extends TokenFilter

  Filter outputs a single token which is a concatenation of the sorted and de-duplicated set of input tokens. This can be useful for clustering/linking use cases.

- - ### 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 int` | `DEFAULT_MAX_OUTPUT_TOKEN_SIZE`
    `static char` | `DEFAULT_SEPARATOR`

    - ### 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
    `FingerprintFilter(TokenStream input)` Create a new FingerprintFilter with default settings
    `FingerprintFilter(TokenStream input, int maxOutputTokenSize, char separator)` Create a new FingerprintFilter with control over all settings

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `end()`
    `boolean` | `incrementToken()`
    `void` | `reset()`

    - ### 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_MAX_OUTPUT_TOKEN_SIZE

          public static final int DEFAULT_MAX_OUTPUT_TOKEN_SIZE

      See Also:
        Constant Field Values

    - #### DEFAULT_SEPARATOR

          public static final char DEFAULT_SEPARATOR

      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### FingerprintFilter

          public FingerprintFilter(TokenStream input)

      Create a new FingerprintFilter with default settings

    - #### FingerprintFilter

          public FingerprintFilter(TokenStream input,
                                   int maxOutputTokenSize,
                                   char separator)

      Create a new FingerprintFilter with control over all settings
      Parameters:
        `input` - the source of tokens to be summarized into a single token
        `maxOutputTokenSize` - the maximum length of the summarized output token. If exceeded, no output token is emitted
        `separator` - the character used to separate tokens combined into the single output token

  - ### Method Detail

    - #### incrementToken

          public final boolean incrementToken()
                                       throws IOException

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

    - #### end

          public final 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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