org.apache.lucene.analysis

## Class LowerCaseFilter

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

- All Implemented Interfaces:
    Closeable, AutoCloseable

      public class LowerCaseFilter
      extends TokenFilter

  Normalizes token text to lower case.

- - ### Nested Class Summary

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

      `AttributeSource.State`

  - ### Field Summary

    - ### 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
    `LowerCaseFilter(TokenStream in)` Create a new LowerCaseFilter, that normalizes token text to lower case.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `boolean` | `incrementToken()` Consumers (i.e., `IndexWriter`) use this method to advance the stream to the next token.

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

      `close, end, reset`

    - ### 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`

- - ### Constructor Detail

    - #### LowerCaseFilter

          public LowerCaseFilter(TokenStream in)

      Create a new LowerCaseFilter, that normalizes token text to lower case.
      Parameters:
        `in` - TokenStream to filter

  - ### Method Detail

    - #### incrementToken

          public final boolean incrementToken()
                                       throws IOException

      Description copied from class: `TokenStream`
      Consumers (i.e., `IndexWriter`) use this method to advance the stream to the next token. Implementing classes must implement this method and update the appropriate `AttributeImpl`s with the attributes of the next token.

      The producer must make no assumptions about the attributes after the method has been returned: the caller may arbitrarily change it. If the producer needs to preserve the state for subsequent calls, it can use `AttributeSource.captureState()` to create a copy of the current attribute state.

      This method is called for every token of a document, so an efficient implementation is crucial for good performance. To avoid calls to `AttributeSource.addAttribute(Class)` and `AttributeSource.getAttribute(Class)`, references to all `AttributeImpl`s that this stream uses should be retrieved during instantiation.

      To ensure that filters and consumers know which attributes are available, the attributes must be added during instantiation. Filters and consumers are not required to check for availability of attributes in `TokenStream.incrementToken()`.

      Specified by:
        `incrementToken` in class `TokenStream`
      Returns:
        false for end of stream; true otherwise
      Throws:
        `IOException`

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