01: // ============================================================================
02: // $Id: FindIteratorFunctor.java,v 1.4 2005/08/02 23:45:05 davidahall Exp $
03: // Copyright (c) 2004-2005 David A. Hall
04: // ============================================================================
05: // The contents of this file are subject to the Common Development and
06: // Distribution License (CDDL), Version 1.0 (the License); you may not use this
07: // file except in compliance with the License. You should have received a copy
08: // of the the License along with this file: if not, a copy of the License is
09: // available from Sun Microsystems, Inc.
10: //
11: // http://www.sun.com/cddl/cddl.html
12: //
13: // From time to time, the license steward (initially Sun Microsystems, Inc.) may
14: // publish revised and/or new versions of the License. You may not use,
15: // distribute, or otherwise make this file available under subsequent versions
16: // of the License.
17: //
18: // Alternatively, the contents of this file may be used under the terms of the
19: // GNU Lesser General Public License Version 2.1 or later (the "LGPL"), in which
20: // case the provisions of the LGPL are applicable instead of those above. If you
21: // wish to allow use of your version of this file only under the terms of the
22: // LGPL, and not to allow others to use your version of this file under the
23: // terms of the CDDL, indicate your decision by deleting the provisions above
24: // and replace them with the notice and other provisions required by the LGPL.
25: // If you do not delete the provisions above, a recipient may use your version
26: // of this file under the terms of either the CDDL or the LGPL.
27: //
28: // This library is distributed in the hope that it will be useful,
29: // but WITHOUT ANY WARRANTY; without even the implied warranty of
30: // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
31: // ============================================================================
32: package net.sf.jga.fn.algorithm;
33:
34: import java.util.Iterator;
35: import net.sf.jga.fn.UnaryFunctor;
36: import net.sf.jga.util.FindIterator;
37:
38: /**
39: * Abstract base class for functors that take an input iterator and return a
40: * FindIterator. This class provides the ability to prevent excessive
41: * iterator wrapping by tracking the identity of the functor that has produced
42: * the wrapped iterator, and not re-wrapping an iterator if it was produced by
43: * the same object that is currently requesting a wrapped iterator.
44: * <p>
45: * Copyright © 2004-2005 David A. Hall
46: *
47: * @author <a href="mailto:davidahall@users.sf.net">David A. Hall</a>
48: */
49:
50: abstract public class FindIteratorFunctor<T> extends
51: UnaryFunctor<Iterator<? extends T>, FindIterator<T>> {
52: /**
53: * Conditionally wraps the input iterator in a FindIterator for return.
54: * Uses a Wrapper to determine if the input iterator is one that this
55: * object has already built and returned: if so, then there is no need
56: * to wrap it again.
57: */
58: protected FindIterator<T> wrap(Iterator<? extends T> iterator) {
59: if (iterator instanceof Wrapper
60: && ((Wrapper) iterator).owner == this )
61: // @SuppressWarnings
62: // The preceding condition can only be true if the iterator argument was
63: // created by the constructor call three lines hence, and will always be
64: // true in that case.
65: return (FindIterator<T>) iterator;
66:
67: return new Wrapper<T>(this , iterator);
68:
69: }
70:
71: /**
72: * Wrapper class used to prevent excessive creation of wrapper interators.
73: * This class stores a reference to its caller (which is an instance of the
74: * enclosing class).
75: */
76: static private class Wrapper<T> extends FindIterator<T> {
77: private FindIteratorFunctor<T> owner;
78:
79: public Wrapper(FindIteratorFunctor<T> owner,
80: Iterator<? extends T> iter) {
81: super(iter);
82: this.owner = owner;
83: }
84: }
85: }
|