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.

  • Field Details

  • Constructor Details

    • 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(UserDictionary userDictionary, boolean discardPunctuation, boolean discardCompoundToken, 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.
      discardCompoundToken - true if compound tokens should be dropped from the output when tokenization mode is not NORMAL.
      mode - tokenization mode.
    • JapaneseTokenizer

      public JapaneseTokenizer(AttributeFactory factory, UserDictionary userDictionary, boolean discardPunctuation, JapaneseTokenizer.Mode mode)
      Create a new JapaneseTokenizer using the system and unknown dictionaries shipped with Lucene.
      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.
    • JapaneseTokenizer

      public JapaneseTokenizer(AttributeFactory factory, UserDictionary userDictionary, boolean discardPunctuation, boolean discardCompoundToken, JapaneseTokenizer.Mode mode)
      Create a new JapaneseTokenizer using the system and unknown dictionaries shipped with Lucene.
      Parameters:
      factory - the AttributeFactory to use
      userDictionary - Optional: if non-null, user dictionary.
      discardPunctuation - true if punctuation tokens should be dropped from the output.
      discardCompoundToken - true if compound tokens should be dropped from the output when tokenization mode is not NORMAL.
      mode - tokenization mode.
    • JapaneseTokenizer

      public JapaneseTokenizer(AttributeFactory factory, TokenInfoDictionary systemDictionary, UnknownDictionary unkDictionary, ConnectionCosts connectionCosts, UserDictionary userDictionary, boolean discardPunctuation, boolean discardCompoundToken, JapaneseTokenizer.Mode mode)
      Create a new JapaneseTokenizer, supplying a custom system dictionary and unknown dictionary. This constructor provides an entry point for users that want to construct custom language models that can be used as input to DictionaryBuilder.
      Parameters:
      factory - the AttributeFactory to use
      systemDictionary - a custom known token dictionary
      unkDictionary - a custom unknown token dictionary
      connectionCosts - custom token transition costs
      userDictionary - Optional: if non-null, user dictionary.
      discardPunctuation - true if punctuation tokens should be dropped from the output.
      discardCompoundToken - true if compound tokens should be dropped from the output when tokenization mode is not NORMAL.
      mode - tokenization mode.
  • Method Details

    • setGraphvizFormatter

      public void setGraphvizFormatter(GraphvizFormatter dotOut)
      Expert: set this to produce graphviz (dot) output of the Viterbi lattice
    • 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
      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
    • resetState

      private void resetState()
    • 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
    • computeSecondBestThreshold

      private int computeSecondBestThreshold(int pos, int length) throws IOException
      Throws:
      IOException
    • computePenalty

      private int computePenalty(int pos, int length) throws IOException
      Throws:
      IOException
    • add

      private void add(Dictionary dict, JapaneseTokenizer.Position fromPosData, int endPos, int wordID, JapaneseTokenizer.Type type, boolean addPenalty) throws IOException
      Throws:
      IOException
    • 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
    • parse

      private void parse() throws IOException
      Throws:
      IOException
    • pruneAndRescore

      private void pruneAndRescore(int startPos, int endPos, int bestStartIDX) throws IOException
      Throws:
      IOException
    • registerNode

      private void registerNode(int node, char[] fragment)
    • fixupPendingList

      private void fixupPendingList()
    • probeDelta

      private int probeDelta(String inText, String requiredToken) throws IOException
      Throws:
      IOException
    • calcNBestCost

      public int calcNBestCost(String examples)
    • setNBestCost

      public void setNBestCost(int value)
    • backtraceNBest

      private void backtraceNBest(JapaneseTokenizer.Position endPosData, boolean useEOS) throws IOException
      Throws:
      IOException
    • backtrace

      private void backtrace(JapaneseTokenizer.Position endPosData, int fromIDX) throws IOException
      Throws:
      IOException
    • getDict

    • isPunctuation

      private static boolean isPunctuation(char ch)