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## org.apache.lucene.collation
Class ICUCollationKeyAnalyzer

    java.lang.Object
      org.apache.lucene.analysis.Analyzer
          org.apache.lucene.collation.ICUCollationKeyAnalyzer

All Implemented Interfaces:
  Closeable

    public final class ICUCollationKeyAnalyzer

extends org.apache.lucene.analysis.Analyzer

Filters `KeywordTokenizer` with `ICUCollationKeyFilter`.

Converts the token into its `CollationKey`, and then encodes the CollationKey with `IndexableBinaryStringTools`, to allow it to be stored as an index term.

WARNING: Make sure you use exactly the same Collator at index and query time -- CollationKeys are only comparable when produced by the same Collator. `RuleBasedCollator`s are independently versioned, so it is safe to search against stored CollationKeys if the following are exactly the same (best practice is to store this information with the index and check that they remain the same at query time):

1. Collator version - see `Collator.getVersion()`
2. The collation strength used - see `Collator.setStrength(int)`

CollationKeys generated by ICU Collators are not compatible with those generated by java.text.Collators. Specifically, if you use ICUCollationKeyAnalyzer to generate index terms, do not use `CollationKeyAnalyzer` on the query side, or vice versa.

ICUCollationKeyAnalyzer is significantly faster and generates significantly shorter keys than CollationKeyAnalyzer. See http://site.icu-project.org/charts/collation-icu4j-sun for key generation timing and key length comparisons between ICU4J and java.text.Collator over several languages.

Constructor Summary
`ICUCollationKeyAnalyzer(com.ibm.icu.text.Collator collator)`

Method Summary
`org.apache.lucene.analysis.TokenStream` | `reusableTokenStream(String fieldName, Reader reader)`
`org.apache.lucene.analysis.TokenStream` | `tokenStream(String fieldName, Reader reader)`

Methods inherited from class org.apache.lucene.analysis.Analyzer
`close, getOffsetGap, getPositionIncrementGap, getPreviousTokenStream, setPreviousTokenStream`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### ICUCollationKeyAnalyzer

    public ICUCollationKeyAnalyzer(com.ibm.icu.text.Collator collator)

Method Detail

### tokenStream

    public org.apache.lucene.analysis.TokenStream tokenStream(String fieldName,
                                                              Reader reader)

  Specified by:
    `tokenStream` in class `org.apache.lucene.analysis.Analyzer`

### reusableTokenStream

    public org.apache.lucene.analysis.TokenStream reusableTokenStream(String fieldName,
                                                                      Reader reader)
                                                               throws IOException

  Overrides:
    `reusableTokenStream` in class `org.apache.lucene.analysis.Analyzer`
  Throws:
    `IOException`

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