russianlettertokenizer.java

一套java版本的搜索引擎源码

package org.apache.lucene.analysis.ru;

/**
 * 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.analysis.CharTokenizer;

/**
 * A RussianLetterTokenizer is a tokenizer that extends LetterTokenizer by additionally looking up letters
 * in a given "russian charset". The problem with LeterTokenizer is that it uses Character.isLetter() method,
 * which doesn't know how to detect letters in encodings like CP1252 and KOI8
 * (well-known problems with 0xD7 and 0xF7 chars)
 *
 * @author  Boris Okner, [e-mail]
 * @version $Id: RussianLetterTokenizer.java 472959 2006-11-09 16:21:50Z yonik $
 */

public class RussianLetterTokenizer extends CharTokenizer
{
    /** Construct a new LetterTokenizer. */
    private char[] charset;

    public RussianLetterTokenizer(Reader in, char[] charset)
    {
        super(in);
        this.charset = charset;
    }

    /**
     * Collects only characters which satisfy
     * {@link Character#isLetter(char)}.
     */
    protected boolean isTokenChar(char c)
    {
        if (Character.isLetter(c))
            return true;
        for (int i = 0; i < charset.length; i++)
        {
            if (c == charset[i])
                return true;
        }
        return false;
    }
}