org.apache.lucene.analysis

## Class TokenFilter

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

- All Implemented Interfaces:
    Closeable, AutoCloseable
  Direct Known Subclasses:
    CachingTokenFilter, FilteringTokenFilter, GraphTokenFilter, LowerCaseFilter

      public abstract class TokenFilter
      extends TokenStream

  A TokenFilter is a TokenStream whose input is another TokenStream.

  This is an abstract class; subclasses must override `TokenStream.incrementToken()`.

  See Also:
    `TokenStream`

- - ### 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
    --- | ---
    `protected TokenStream` | `input` The source of tokens for this filter.

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

      `DEFAULT_TOKEN_ATTRIBUTE_FACTORY`

  - ### Constructor Summary

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `protected` | `TokenFilter(TokenStream input)` Construct a token stream filtering the given input.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `close()` Releases resources associated with this stream.
    `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).
    `void` | `reset()` This method is called by a consumer before it begins consumption using `TokenStream.incrementToken()`.

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

      `incrementToken`

    - ### 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

    - #### input

          protected final TokenStream input

      The source of tokens for this filter.

  - ### Constructor Detail

    - #### TokenFilter

          protected TokenFilter(TokenStream input)

      Construct a token stream filtering the given input.

  - ### Method Detail

    - #### end

          public void end()
                   throws IOException

      This method is called by the consumer after the last token has been consumed, after `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.

      Additionally any skipped positions (such as those removed by a stopfilter) can be applied to the position increment, or any adjustment of other attributes where the end-of-stream value may be important.

      If you override this method, always call `super.end()`.

      NOTE: The default implementation chains the call to the input TokenStream, so be sure to call `super.end()` first when overriding this method.

      Overrides:
        `end` in class `TokenStream`
      Throws:
        `IOException` - If an I/O error occurs

    - #### close

          public void close()
                     throws IOException

      Releases resources associated with this stream.

      If you override this method, always call `super.close()`, otherwise some internal state will not be correctly reset (e.g., `Tokenizer` will throw `IllegalStateException` on reuse).

      NOTE: The default implementation chains the call to the input TokenStream, so be sure to call `super.close()` when overriding this method.

      Specified by:
        `close` in interface `Closeable`
      Specified by:
        `close` in interface `AutoCloseable`
      Overrides:
        `close` in class `TokenStream`
      Throws:
        `IOException`

    - #### reset

          public void reset()
                     throws IOException

      This method is called by a consumer before it begins consumption using `TokenStream.incrementToken()`.

      Resets this stream to a clean state. Stateful implementations must implement this method so that they can be reused, just as if they had been created fresh.

      If you override this method, always call `super.reset()`, otherwise some internal state will not be correctly reset (e.g., `Tokenizer` will throw `IllegalStateException` on further usage).

      NOTE: The default implementation chains the call to the input TokenStream, so be sure to call `super.reset()` when overriding this method.

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

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