01: /* Copyright (C) 2004 - 2007 db4objects Inc. http://www.db4o.com
02:
03: This file is part of the db4o open source object database.
04:
05: db4o is free software; you can redistribute it and/or modify it under
06: the terms of version 2 of the GNU General Public License as published
07: by the Free Software Foundation and as clarified by db4objects' GPL
08: interpretation policy, available at
09: 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 _current;
31:
32: public static final Object SKIP = new Object();
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 map(final Object 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 current() {
61: if (Iterators.NO_ELEMENT == _current) {
62: throw new IllegalStateException();
63: }
64: return _current;
65: }
66: }
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