org.apache.lucene.analysis.ja

Class JapaneseTokenizer

  • All Implemented Interfaces:
    Closeable, AutoCloseable


    public final class JapaneseTokenizer
    extends Tokenizer
    Tokenizer for Japanese that uses morphological analysis.

    This tokenizer sets a number of additional attributes:

    This tokenizer uses a rolling Viterbi search to find the least cost segmentation (path) of the incoming characters. For tokens that appear to be compound (> length 2 for all Kanji, or > length 7 for non-Kanji), we see if there is a 2nd best segmentation of that token after applying penalties to the long tokens. If so, and the Mode is JapaneseTokenizer.Mode.SEARCH, we output the alternate segmentation as well.

    • Constructor Detail

      • JapaneseTokenizer

        public JapaneseTokenizer(UserDictionary userDictionary,
                                 boolean discardPunctuation,
                                 JapaneseTokenizer.Mode mode)
        Create a new JapaneseTokenizer.

        Uses the default AttributeFactory.

        Parameters:
        userDictionary - Optional: if non-null, user dictionary.
        discardPunctuation - true if punctuation tokens should be dropped from the output.
        mode - tokenization mode.
      • JapaneseTokenizer

        public JapaneseTokenizer(AttributeFactory factory,
                                 UserDictionary userDictionary,
                                 boolean discardPunctuation,
                                 JapaneseTokenizer.Mode mode)
        Create a new JapaneseTokenizer.
        Parameters:
        factory - the AttributeFactory to use
        userDictionary - Optional: if non-null, user dictionary.
        discardPunctuation - true if punctuation tokens should be dropped from the output.
        mode - tokenization mode.
    • Method Detail

      • 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 Closeable
        Specified by:
        close in interface AutoCloseable
        Overrides:
        close in class Tokenizer
        Throws:
        IOException
      • 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).

        Overrides:
        reset in class Tokenizer
        Throws:
        IOException
      • end

        public 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().

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

        public 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
        Returns:
        false for end of stream; true otherwise
        Throws:
        IOException