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Java > Open Source Codes > net > sf > jga > fn > algorithm > FindIteratorFunctor


1 // ============================================================================
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// $Id: FindIteratorFunctor.java,v 1.4 2005/08/02 23:45:05 davidahall Exp $
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// Copyright (c) 2004-2005 David A. Hall
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// ============================================================================
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// The contents of this file are subject to the Common Development and
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// Distribution License (CDDL), Version 1.0 (the License); you may not use this
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// file except in compliance with the License. You should have received a copy
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// of the the License along with this file: if not, a copy of the License is
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// available from Sun Microsystems, Inc.
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//
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// http://www.sun.com/cddl/cddl.html
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//
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// From time to time, the license steward (initially Sun Microsystems, Inc.) may
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// publish revised and/or new versions of the License. You may not use,
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// distribute, or otherwise make this file available under subsequent versions
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// of the License.
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//
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// Alternatively, the contents of this file may be used under the terms of the
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// GNU Lesser General Public License Version 2.1 or later (the "LGPL"), in which
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// case the provisions of the LGPL are applicable instead of those above. If you
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// wish to allow use of your version of this file only under the terms of the
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// LGPL, and not to allow others to use your version of this file under the
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// terms of the CDDL, indicate your decision by deleting the provisions above
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// and replace them with the notice and other provisions required by the LGPL.
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// If you do not delete the provisions above, a recipient may use your version
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// of this file under the terms of either the CDDL or the LGPL.
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//
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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// ============================================================================
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package net.sf.jga.fn.algorithm;
33
34 import java.util.Iterator JavaDoc;
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 &copy; 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>
51     extends UnaryFunctor<Iterator JavaDoc<? extends T>, FindIterator<T>>
52 {
53     /**
54      * Conditionally wraps the input iterator in a FindIterator for return.
55      * Uses a Wrapper to determine if the input iterator is one that this
56      * object has already built and returned: if so, then there is no need
57      * to wrap it again.
58      */

59     protected FindIterator<T> wrap(Iterator JavaDoc<? extends T> iterator) {
60         if (iterator instanceof Wrapper && ((Wrapper)iterator).owner == this)
61             // @SuppressWarnings
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// The preceding condition can only be true if the iterator argument was
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// created by the constructor call three lines hence, and will always be
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// true in that case.
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return (FindIterator<T>) iterator;
66   
67         return new Wrapper<T>(this, iterator);
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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         public Wrapper(FindIteratorFunctor<T> owner, Iterator JavaDoc<? extends T> iter) {
79             super(iter); this.owner = owner;
80         }
81     }
82 }
83
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