Class KoreanTokenizer

  • All Implemented Interfaces:
    java.io.Closeable, java.lang.AutoCloseable

    public final class KoreanTokenizer
    extends Tokenizer
    Tokenizer for Korean 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.

    • Constructor Detail

      • KoreanTokenizer

        public KoreanTokenizer()
        Creates a new KoreanTokenizer with default parameters.

        Uses the default AttributeFactory.

      • KoreanTokenizer

        public KoreanTokenizer​(AttributeFactory factory,
                               UserDictionary userDictionary,
                               KoreanTokenizer.DecompoundMode mode,
                               boolean outputUnknownUnigrams)
        Create a new KoreanTokenizer.
        Parameters:
        factory - the AttributeFactory to use
        userDictionary - Optional: if non-null, user dictionary.
        mode - Decompound mode.
        outputUnknownUnigrams - If true outputs unigrams for unknown words.
      • KoreanTokenizer

        public KoreanTokenizer​(AttributeFactory factory,
                               UserDictionary userDictionary,
                               KoreanTokenizer.DecompoundMode mode,
                               boolean outputUnknownUnigrams,
                               boolean discardPunctuation)
        Create a new KoreanTokenizer.
        Parameters:
        factory - the AttributeFactory to use
        userDictionary - Optional: if non-null, user dictionary.
        mode - Decompound mode.
        outputUnknownUnigrams - If true outputs unigrams for unknown words.
        discardPunctuation - true if punctuation tokens should be dropped from the output.
    • Method Detail

      • setGraphvizFormatter

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

        public void close()
                   throws java.io.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 java.lang.AutoCloseable
        Specified by:
        close in interface java.io.Closeable
        Overrides:
        close in class Tokenizer
        Throws:
        java.io.IOException
      • reset

        public void reset()
                   throws java.io.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:
        java.io.IOException
      • resetState

        private void resetState()
      • end

        public void end()
                 throws java.io.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:
        java.io.IOException - If an I/O error occurs
      • computeSpacePenalty

        private int computeSpacePenalty​(POS.Tag leftPOS,
                                        int numSpaces)
        Returns the space penalty associated with the provided POS.Tag.
        Parameters:
        leftPOS - the left part of speech of the current token.
        numSpaces - the number of spaces before the current token.
      • incrementToken

        public boolean incrementToken()
                               throws java.io.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:
        java.io.IOException
      • parse

        private void parse()
                    throws java.io.IOException
        Throws:
        java.io.IOException
      • shouldFilterToken

        private boolean shouldFilterToken​(Token token)
      • isPunctuation

        private static boolean isPunctuation​(char ch)
      • isPunctuation

        private static boolean isPunctuation​(char ch,
                                             int cid)
      • isCommonOrInherited

        private static boolean isCommonOrInherited​(java.lang.Character.UnicodeScript script)
      • isSameScript

        private static boolean isSameScript​(java.lang.Character.UnicodeScript scriptOne,
                                            java.lang.Character.UnicodeScript scriptTwo)
        Determine if two scripts are compatible.