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Lucene example source code file (ICUFoldingFilter.java)

This example Lucene source code file (ICUFoldingFilter.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lucene tags/keywords

icufoldingfilter, icufoldingfilter, icunormalizer2filter, icunormalizer2filter, normalizer2, normalizer2

The Lucene ICUFoldingFilter.java source code

package org.apache.lucene.analysis.icu;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import org.apache.lucene.analysis.TokenStream;

import com.ibm.icu.text.Normalizer2;

/**
 * A TokenFilter that applies search term folding to Unicode text,
 * applying foldings from UTR#30 Character Foldings.
 * <p>
 * This filter applies the following foldings from the report to unicode text:
 * <ul>
 * <li>Accent removal
 * <li>Case folding
 * <li>Canonical duplicates folding
 * <li>Dashes folding
 * <li>Diacritic removal (including stroke, hook, descender)
 * <li>Greek letterforms folding
 * <li>Han Radical folding
 * <li>Hebrew Alternates folding
 * <li>Jamo folding
 * <li>Letterforms folding
 * <li>Math symbol folding
 * <li>Multigraph Expansions: All
 * <li>Native digit folding
 * <li>No-break folding
 * <li>Overline folding
 * <li>Positional forms folding
 * <li>Small forms folding
 * <li>Space folding
 * <li>Spacing Accents folding
 * <li>Subscript folding
 * <li>Superscript folding
 * <li>Suzhou Numeral folding
 * <li>Symbol folding
 * <li>Underline folding
 * <li>Vertical forms folding
 * <li>Width folding
 * </ul>
 * <p>
 * Additionally, Default Ignorables are removed, and text is normalized to NFKC.
 * All foldings, case folding, and normalization mappings are applied recursively
 * to ensure a fully folded and normalized result.
 * </p>
 */
public final class ICUFoldingFilter extends ICUNormalizer2Filter {
  private static final Normalizer2 normalizer =  Normalizer2.getInstance(
      ICUFoldingFilter.class.getResourceAsStream("utr30.nrm"), 
      "utr30", Normalizer2.Mode.COMPOSE);
  
  /**
   * Create a new ICUFoldingFilter on the specified input
   */
  public ICUFoldingFilter(TokenStream input) {
    super(input, normalizer);
  }
}

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