org.apache.lucene.analysis
Class CharTokenizer

java.lang.Object
  org.apache.lucene.analysis.TokenStream
      org.apache.lucene.analysis.Tokenizer
          org.apache.lucene.analysis.CharTokenizer

Direct Known Subclasses:

LetterTokenizer, RussianLetterTokenizer, WhitespaceTokenizer

public abstract class CharTokenizer
extends Tokenizer

An abstract base class for simple, character-oriented tokenizers.

Field Summary

Fields inherited from class org.apache.lucene.analysis.Tokenizer

input

Constructor Summary

CharTokenizer(Reader input)

Method Summary

protected abstract boolean	isTokenChar(char c) Returns true iff a character should be included in a token.
Token	next(Token reusableToken) Returns the next token in the stream, or null at EOS.
protected char	normalize(char c) Called on each token character to normalize it before it is added to the token.
void	reset(Reader input) Expert: Reset the tokenizer to a new reader.

Methods inherited from class org.apache.lucene.analysis.Tokenizer

close

Methods inherited from class org.apache.lucene.analysis.TokenStream

next, reset

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CharTokenizer

public CharTokenizer(Reader input)

Method Detail

isTokenChar

protected abstract boolean isTokenChar(char c)

Returns true iff a character should be included in a token. This tokenizer generates as tokens adjacent sequences of characters which satisfy this predicate. Characters for which this is false are used to define token boundaries and are not included in tokens.

normalize

protected char normalize(char c)

Called on each token character to normalize it before it is added to the token. The default implementation does nothing. Subclasses may use this to, e.g., lowercase tokens.

next

public final Token next(Token reusableToken)
                 throws IOException

Description copied from class: TokenStream

Returns the next token in the stream, or null at EOS. When possible, the input Token should be used as the returned Token (this gives fastest tokenization performance), but this is not required and a new Token may be returned. Callers may re-use a single Token instance for successive calls to this method.

This implicitly defines a "contract" between consumers (callers of this method) and producers (implementations of this method that are the source for tokens):

• A consumer must fully consume the previously returned Token before calling this method again.
• A producer must call Token.clear() before setting the fields in it & returning it

Also, the producer must make no assumptions about a Token after it has been returned: the caller may arbitrarily change it. If the producer needs to hold onto the token for subsequent calls, it must clone() it before storing it. Note that a TokenFilter is considered a consumer.

Overrides:

next in class TokenStream

Parameters:

reusableToken - a Token that may or may not be used to return; this parameter should never be null (the callee is not required to check for null before using it, but it is a good idea to assert that it is not null.)

Returns:

next token in the stream or null if end-of-stream was hit

Throws:

IOException

reset

public void reset(Reader input)
           throws IOException

Description copied from class: Tokenizer

Expert: Reset the tokenizer to a new reader. Typically, an analyzer (in its reusableTokenStream method) will use this to re-use a previously created tokenizer.

Overrides:

reset in class Tokenizer

Throws:

IOException