LetterTokenizer.java

package org.apache.lucene.analysis;

/**
 * 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 java.io.Reader;

import org.apache.lucene.util.AttributeSource;

/** A LetterTokenizer is a tokenizer that divides text at non-letters.  That's
  to say, it defines tokens as maximal strings of adjacent letters, as defined
  by java.lang.Character.isLetter() predicate.

  Note: this does a decent job for most European languages, but does a terrible
  job for some Asian languages, where words are not separated by spaces. */

public class LetterTokenizer extends CharTokenizer {
  /** Construct a new LetterTokenizer. */
  public LetterTokenizer(Reader in) {
    super(in);
  }
  
  /** Construct a new LetterTokenizer using a given {@link AttributeSource}. */
  public LetterTokenizer(AttributeSource source, Reader in) {
    super(source, in);
  }
  
  /** Construct a new LetterTokenizer using a given {@link org.apache.lucene.util.AttributeSource.AttributeFactory}. */
  public LetterTokenizer(AttributeFactory factory, Reader in) {
    super(factory, in);
  }

  /** Collects only characters which satisfy
   * {@link Character#isLetter(char)}.*/
  @Override
  protected boolean isTokenChar(char c) {
    return Character.isLetter(c);
  }
}