1 /**
2 * This file Copyright (c) 2011 Magnolia International
3 * Ltd. (http://www.magnolia-cms.com). All rights reserved.
4 *
5 *
6 * This file is dual-licensed under both the Magnolia
7 * Network Agreement and the GNU General Public License.
8 * You may elect to use one or the other of these licenses.
9 *
10 * This file is distributed in the hope that it will be
11 * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
12 * implied warranty of MERCHANTABILITY or FITNESS FOR A
13 * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
14 * Redistribution, except as permitted by whichever of the GPL
15 * or MNA you select, is prohibited.
16 *
17 * 1. For the GPL license (GPL), you can redistribute and/or
18 * modify this file under the terms of the GNU General
19 * Public License, Version 3, as published by the Free Software
20 * Foundation. You should have received a copy of the GNU
21 * General Public License, Version 3 along with this program;
22 * if not, write to the Free Software Foundation, Inc., 51
23 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
24 *
25 * 2. For the Magnolia Network Agreement (MNA), this file
26 * and the accompanying materials are made available under the
27 * terms of the MNA which accompanies this distribution, and
28 * is available at http://www.magnolia-cms.com/mna.html
29 *
30 * Any modifications to this file must keep this entire header
31 * intact.
32 *
33 */
34 package info.magnolia.jcr.iterator;
35
36 import java.util.Iterator;
37 import java.util.NoSuchElementException;
38 import javax.jcr.RangeIterator;
39
40 import org.apache.jackrabbit.commons.predicate.Predicate;
41
42
43 /**
44 * Base class for implementing filtering JCR iterators. Does not support getSize() since that would require iterating
45 * through the entire target iterator to count the number of nodes that match the predicate.
46 *
47 * @param <T>
48 * @version $Id$
49 */
50 public class FilteringRangeIterator<T> implements RangeIterator {
51
52 private final Iterator<T> iterator;
53 private final Predicate predicate;
54 private long position;
55 private T next;
56
57 public FilteringRangeIterator(Iterator<T> iterator, Predicate predicate) {
58 this.iterator = iterator;
59 this.predicate = predicate;
60 }
61
62 @Override
63 public boolean hasNext() {
64 while (next == null && iterator.hasNext()) {
65 T n = iterator.next();
66 if (predicate.evaluate(n)) {
67 next = n;
68 }
69 }
70 return next != null;
71 }
72
73 @Override
74 public T next() {
75 if (!hasNext()) {
76 throw new NoSuchElementException();
77 }
78 T t = next;
79 next = null;
80 position++;
81 return t;
82 }
83
84 @Override
85 public void remove() {
86 iterator.remove();
87 }
88
89 @Override
90 public long getPosition() {
91 return position;
92 }
93
94 @Override
95 public void skip(long skipNum) {
96 while (skipNum-- > 0)
97 next();
98 }
99
100 @Override
101 public long getSize() {
102 // getSize() is optional and we don't support it since that would require walking through the entire iterator
103 return -1;
104 }
105 }