org.apache.lucene.analysis.ja
Class JapaneseKatakanaStemFilter

java.lang.Object
  org.apache.lucene.util.AttributeSource
      org.apache.lucene.analysis.TokenStream
          org.apache.lucene.analysis.TokenFilter
              org.apache.lucene.analysis.ja.JapaneseKatakanaStemFilter

All Implemented Interfaces:

Closeable

public final class JapaneseKatakanaStemFilter
extends TokenFilter

A TokenFilter that normalizes common katakana spelling variations ending in a long sound character by removing this character (U+30FC). Only katakana words longer than a minimum length are stemmed (default is four).

Note that only full-width katakana characters are supported. Please use a CJKWidthFilter to convert half-width katakana to full-width before using this filter.

In order to prevent terms from being stemmed, use an instance of KeywordMarkerFilter or a custom TokenFilter that sets the KeywordAttribute before this TokenStream.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource

AttributeSource.AttributeFactory, AttributeSource.State

Field Summary

static int

DEFAULT_MINIMUM_LENGTH

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

input

Constructor Summary

JapaneseKatakanaStemFilter(TokenStream input)

JapaneseKatakanaStemFilter(TokenStream input, int minimumLength)

Method Summary

boolean

incrementToken() Consumers (i.e., IndexWriter) use this method to advance the stream to the next token.

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

close, end, reset

Methods inherited from class org.apache.lucene.util.AttributeSource

addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, restoreState, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

DEFAULT_MINIMUM_LENGTH

public static final int DEFAULT_MINIMUM_LENGTH

See Also:

Constant Field Values

Constructor Detail

JapaneseKatakanaStemFilter

public JapaneseKatakanaStemFilter(TokenStream input,
                                  int minimumLength)

JapaneseKatakanaStemFilter

public JapaneseKatakanaStemFilter(TokenStream input)

Method Detail

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