Class LowerCaseFilter

All Implemented Interfaces:
Closeable, AutoCloseable, Unwrappable<TokenStream>

public class LowerCaseFilter extends TokenFilter
Normalizes token text to lower case.
  • Constructor Details

    • LowerCaseFilter

      public LowerCaseFilter(TokenStream in)
      Create a new LowerCaseFilter, that normalizes token text to lower case.
      in - TokenStream to filter
  • Method Details

    • 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 AttributeImpls 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 AttributeImpls 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
      false for end of stream; true otherwise