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## org.apache.lucene.analysis.ja
Class JapaneseTokenizer

    java.lang.Object
      org.apache.lucene.util.AttributeSource
          org.apache.lucene.analysis.TokenStream
              org.apache.lucene.analysis.Tokenizer
                  org.apache.lucene.analysis.ja.JapaneseTokenizer

All Implemented Interfaces:
  Closeable

    public final class JapaneseTokenizer

extends Tokenizer

Tokenizer for Japanese that uses morphological analysis.

This tokenizer sets a number of additional attributes:

- `BaseFormAttribute` containing base form for inflected adjectives and verbs.
- `PartOfSpeechAttribute` containing part-of-speech.
- `ReadingAttribute` containing reading and pronunciation.
- `InflectionAttribute` containing additional part-of-speech information for inflected forms.

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.

Nested Class Summary
`static class` | `JapaneseTokenizer.Mode` Tokenization mode: this determines how the tokenizer handles compound and unknown words.

Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
`AttributeSource.AttributeFactory, AttributeSource.State`

Field Summary
`static JapaneseTokenizer.Mode` | `DEFAULT_MODE` Default tokenization mode.

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

Constructor Summary
`JapaneseTokenizer(Reader input, UserDictionary userDictionary, boolean discardPunctuation, JapaneseTokenizer.Mode mode)` Create a new JapaneseTokenizer.

Method Summary
`void` | `end()` This method is called by the consumer after the last token has been consumed, after `TokenStream.incrementToken()` returned `false` (using the new `TokenStream` API).
`boolean` | `incrementToken()` Consumers (i.e., `IndexWriter`) use this method to advance the stream to the next token.
`void` | `reset()` Resets this stream to the beginning.
`void` | `reset(Reader input)` Expert: Reset the tokenizer to a new reader.
`void` | `setGraphvizFormatter(GraphvizFormatter dotOut)` Expert: set this to produce graphviz (dot) output of the Viterbi lattice

Methods inherited from class org.apache.lucene.analysis.Tokenizer
`close, correctOffset`

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_MODE

    public static final JapaneseTokenizer.Mode DEFAULT_MODE

  Default tokenization mode. Currently this is `JapaneseTokenizer.Mode.SEARCH`.

Constructor Detail

### JapaneseTokenizer

    public JapaneseTokenizer(Reader input,
                             UserDictionary userDictionary,
                             boolean discardPunctuation,
                             JapaneseTokenizer.Mode mode)

  Create a new JapaneseTokenizer.

  Parameters:
    `input` - Reader containing text
    `userDictionary` - Optional: if non-null, user dictionary.
    `discardPunctuation` - true if punctuation tokens should be dropped from the output.
    `mode` - tokenization mode.

Method Detail

### setGraphvizFormatter

    public void setGraphvizFormatter(GraphvizFormatter dotOut)

  Expert: set this to produce graphviz (dot) output of the Viterbi lattice

### 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`

### reset

    public void reset()
               throws IOException

  Description copied from class: `TokenStream`
  Resets this stream to the beginning. This is an optional operation, so subclasses may or may not implement this method. `TokenStream.reset()` is not needed for the standard indexing process. However, if the tokens of a `TokenStream` are intended to be consumed more than once, it is necessary to implement `TokenStream.reset()`. Note that if your TokenStream caches tokens and feeds them back again after a reset, it is imperative that you clone the tokens when you store them away (on the first pass) as well as when you return them (on future passes after `TokenStream.reset()`).

  Overrides:
    `reset` in class `TokenStream`
  Throws:
    `IOException`

### end

    public void end()

  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.

  Overrides:
    `end` in class `TokenStream`

### 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 `AttributeImpl`s 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 `AttributeImpl`s 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`

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