1 package org.apache.lucene.analysis;
4 * Licensed to the Apache Software Foundation (ASF) under one or more
5 * contributor license agreements. See the NOTICE file distributed with
6 * this work for additional information regarding copyright ownership.
7 * The ASF licenses this file to You under the Apache License, Version 2.0
8 * (the "License"); you may not use this file except in compliance with
9 * the License. You may obtain a copy of the License at
11 * http://www.apache.org/licenses/LICENSE-2.0
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS,
15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
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20 import java.io.IOException;
21 import java.util.Iterator;
22 import java.util.LinkedList;
23 import java.util.List;
25 import org.apache.lucene.util.AttributeSource;
28 * This class can be used if the token attributes of a TokenStream
29 * are intended to be consumed more than once. It caches
30 * all token attribute states locally in a List.
32 * <P>CachingTokenFilter implements the optional method
33 * {@link TokenStream#reset()}, which repositions the
34 * stream to the first Token.
36 public final class CachingTokenFilter extends TokenFilter {
37 private List<AttributeSource.State> cache = null;
38 private Iterator<AttributeSource.State> iterator = null;
39 private AttributeSource.State finalState;
41 public CachingTokenFilter(TokenStream input) {
46 public final boolean incrementToken() throws IOException {
49 cache = new LinkedList<AttributeSource.State>();
51 iterator = cache.iterator();
54 if (!iterator.hasNext()) {
55 // the cache is exhausted, return false
58 // Since the TokenFilter can be reset, the tokens need to be preserved as immutable.
59 restoreState(iterator.next());
64 public final void end() throws IOException {
65 if (finalState != null) {
66 restoreState(finalState);
71 public void reset() throws IOException {
73 iterator = cache.iterator();
77 private void fillCache() throws IOException {
78 while(input.incrementToken()) {
79 cache.add(captureState());
81 // capture final state
83 finalState = captureState();