Package org.apache.lucene.analysis.util

Class CharTokenizer

java.lang.Object
org.apache.lucene.util.AttributeSource
org.apache.lucene.analysis.TokenStream
org.apache.lucene.analysis.Tokenizer
org.apache.lucene.analysis.util.CharTokenizer
All Implemented Interfaces:
Closeable, AutoCloseable
Direct Known Subclasses:
CRTokenizer, IndicTokenizer, LetterTokenizer, RussianLetterTokenizer, WhitespaceTokenizer
public abstract class CharTokenizer extends Tokenizer
An abstract base class for simple, character-oriented tokenizers.

You must specify the required Version compatibility when creating CharTokenizer:

  • As of 3.1, CharTokenizer uses an int based API to normalize and detect token codepoints. See isTokenChar(int) and normalize(int) for details.

A new CharTokenizer API has been introduced with Lucene 3.1. This API moved from UTF-16 code units to UTF-32 codepoints to eventually add support for supplementary characters. The old char based API has been deprecated and should be replaced with the int based methods isTokenChar(int) and normalize(int).

As of Lucene 3.1 each CharTokenizer - constructor expects a Version argument. Based on the given Version either the new API or a backwards compatibility layer is used at runtime. For Version invalid input: '<' 3.1 the backwards compatibility layer ensures correct behavior even for indexes build with previous versions of Lucene. If a Version >= 3.1 is used CharTokenizer requires the new API to be implemented by the instantiated class. Yet, the old char based API is not required anymore even if backwards compatibility must be preserved. CharTokenizer subclasses implementing the new API are fully backwards compatible if instantiated with Version invalid input: '<' 3.1.

Note: If you use a subclass of CharTokenizer with Version >= 3.1 on an index build with a version invalid input: '<' 3.1, created tokens might not be compatible with the terms in your index.

  • Constructor Details

    • CharTokenizer

      public CharTokenizer(Version matchVersion, Reader input)
      Creates a new CharTokenizer instance
      Parameters:
      matchVersion - Lucene version to match
      input - the input to split up into tokens

    • CharTokenizer

      public CharTokenizer(Version matchVersion, AttributeSource.AttributeFactory factory, Reader input)
      Creates a new CharTokenizer instance
      Parameters:
      matchVersion - Lucene version to match
      factory - the attribute factory to use for this Tokenizer
      input - the input to split up into tokens

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

    • 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().

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

    • 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