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Java > Open Source Codes > com > db4o > foundation > MappingIterator


1 /* Copyright (C) 2004 - 2006 db4objects Inc. http://www.db4o.com
2
3 This file is part of the db4o open source object database.
4
5 db4o is free software; you can redistribute it and/or modify it under
6 the terms of version 2 of the GNU General Public License as published
7 by the Free Software Foundation and as clarified by db4objects' GPL
8 interpretation policy, available at
9 http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
10 Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
11 Suite 350, San Mateo, CA 94403, USA.
12
13 db4o is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 for more details.
17
18 You should have received a copy of the GNU General Public License along
19 with this program; if not, write to the Free Software Foundation, Inc.,
20 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
21 package com.db4o.foundation;
22
23 /**
24  * @exclude
25  */
26 public abstract class MappingIterator implements Iterator4 {
27
28     private final Iterator4 _iterator;
29
30     private Object JavaDoc _current;
31     
32     public static final Object JavaDoc SKIP = new Object JavaDoc();
33
34     public MappingIterator(Iterator4 iterator) {
35         if (null == iterator) {
36             throw new ArgumentNullException();
37         }
38         _iterator = iterator;
39         _current = Iterators.NO_ELEMENT;
40     }
41     
42     protected abstract Object JavaDoc map(final Object JavaDoc current);
43
44     public boolean moveNext() {
45         do {
46             if (!_iterator.moveNext()) {
47                 _current = Iterators.NO_ELEMENT;
48                 return false;
49             }
50             _current = map(_iterator.current());
51         } while(_current == SKIP);
52         return true;
53     }
54     
55     public void reset() {
56         _current = Iterators.NO_ELEMENT;
57         _iterator.reset();
58     }
59
60     public Object JavaDoc current() {
61         if (Iterators.NO_ELEMENT == _current) {
62             throw new IllegalStateException JavaDoc();
63         }
64         return _current;
65     }
66 }
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