| package org.apache.lucene.analysis; |
| |
| /* ==================================================================== |
| * The Apache Software License, Version 1.1 |
| * |
| * Copyright (c) 2001 The Apache Software Foundation. All rights |
| * reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in |
| * the documentation and/or other materials provided with the |
| * distribution. |
| * |
| * 3. The end-user documentation included with the redistribution, |
| * if any, must include the following acknowledgment: |
| * "This product includes software developed by the |
| * Apache Software Foundation (http://www.apache.org/)." |
| * Alternately, this acknowledgment may appear in the software itself, |
| * if and wherever such third-party acknowledgments normally appear. |
| * |
| * 4. The names "Apache" and "Apache Software Foundation" and |
| * "Apache Lucene" must not be used to endorse or promote products |
| * derived from this software without prior written permission. For |
| * written permission, please contact apache@apache.org. |
| * |
| * 5. Products derived from this software may not be called "Apache", |
| * "Apache Lucene", nor may "Apache" appear in their name, without |
| * prior written permission of the Apache Software Foundation. |
| * |
| * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED |
| * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
| * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR |
| * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF |
| * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |
| * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
| * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT |
| * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| * ==================================================================== |
| * |
| * This software consists of voluntary contributions made by many |
| * individuals on behalf of the Apache Software Foundation. For more |
| * information on the Apache Software Foundation, please see |
| * <http://www.apache.org/>. |
| */ |
| |
| import java.io.IOException; |
| import java.util.Hashtable; |
| |
| /** Removes stop words from a token stream. */ |
| |
| public final class StopFilter extends TokenFilter { |
| |
| private Hashtable table; |
| |
| /** Constructs a filter which removes words from the input |
| TokenStream that are named in the array of words. */ |
| public StopFilter(TokenStream in, String[] stopWords) { |
| input = in; |
| table = makeStopTable(stopWords); |
| } |
| |
| /** Constructs a filter which removes words from the input |
| TokenStream that are named in the Hashtable. */ |
| public StopFilter(TokenStream in, Hashtable stopTable) { |
| input = in; |
| table = stopTable; |
| } |
| |
| /** Builds a Hashtable from an array of stop words, appropriate for passing |
| into the StopFilter constructor. This permits this table construction to |
| be cached once when an Analyzer is constructed. */ |
| public final static Hashtable makeStopTable(String[] stopWords) { |
| Hashtable stopTable = new Hashtable(stopWords.length); |
| for (int i = 0; i < stopWords.length; i++) |
| stopTable.put(stopWords[i], stopWords[i]); |
| return stopTable; |
| } |
| |
| /** Returns the next input Token whose termText() is not a stop word. */ |
| public final Token next() throws IOException { |
| // return the first non-stop word found |
| for (Token token = input.next(); token != null; token = input.next()) |
| if (table.get(token.termText) == null) |
| return token; |
| // reached EOS -- return null |
| return null; |
| } |
| } |