Class StandardTokenizer

All Implemented Interfaces:
Closeable, AutoCloseable

public final class StandardTokenizer extends Tokenizer
A grammar-based tokenizer constructed with JFlex.

This class implements the Word Break rules from the Unicode Text Segmentation algorithm, as specified in Unicode Standard Annex #29.

Many applications have specific tokenizer needs. If this tokenizer does not suit your application, please consider copying this source code directory to your project and maintaining your own grammar-based tokenizer.

  • Field Details


      public static final int ALPHANUM
      Alpha/numeric token type
      See Also:
    • NUM

      public static final int NUM
      Numeric token type
      See Also:

      public static final int SOUTHEAST_ASIAN
      Southeast Asian token type
      See Also:

      public static final int IDEOGRAPHIC
      Ideographic token type
      See Also:

      public static final int HIRAGANA
      Hiragana token type
      See Also:

      public static final int KATAKANA
      Katakana token type
      See Also:
    • HANGUL

      public static final int HANGUL
      Hangul token type
      See Also:
    • EMOJI

      public static final int EMOJI
      Emoji token type.
      See Also:

      public static final String[] TOKEN_TYPES
      String token types that correspond to token type int constants

      public static final int MAX_TOKEN_LENGTH_LIMIT
      Absolute maximum sized token
      See Also:
  • Constructor Details

    • StandardTokenizer

      public StandardTokenizer()
      Creates a new instance of the StandardTokenizer. Attaches the input to the newly created JFlex scanner.


    • StandardTokenizer

      public StandardTokenizer(AttributeFactory factory)
      Creates a new StandardTokenizer with a given AttributeFactory
  • Method Details

    • setMaxTokenLength

      public void setMaxTokenLength(int length)
      Set the max allowed token length. Tokens larger than this will be chopped up at this token length and emitted as multiple tokens. If you need to skip such large tokens, you could increase this max length, and then use LengthFilter to remove long tokens. The default is StandardAnalyzer.DEFAULT_MAX_TOKEN_LENGTH.
      IllegalArgumentException - if the given length is outside of the range [1, 1048576].
    • getMaxTokenLength

      public int getMaxTokenLength()
      Returns the current maximum token length
      See Also:
    • 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
    • end

      public final void end() throws IOException
      Description copied from class: TokenStream
      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().

      end in class TokenStream
      IOException - If an I/O error occurs
    • close

      public void close() throws IOException
      Description copied from class: Tokenizer
      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 closes the input Reader, so be sure to call super.close() when overriding this method.

      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      close in class Tokenizer
    • reset

      public void reset() throws IOException
      Description copied from class: TokenStream
      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).

      reset in class Tokenizer