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Java > Open Source Codes > net > sf > jga > util > IteratorComparator


1 // ============================================================================
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// $Id: IteratorComparator.java,v 1.9 2005/08/02 23:45:22 davidahall Exp $
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// Copyright (c) 2003-2005 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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// ============================================================================
32

33 package net.sf.jga.util;
34
35 import java.io.Serializable JavaDoc;
36 import java.util.Comparator JavaDoc;
37 import java.util.Iterator JavaDoc;
38 import net.sf.jga.fn.comparison.Equality;
39
40 /**
41  * Comparator used to compare iterations lexically.
42  *
43  * @author <a HREF="mailto:davidahall@users.sf.net">David A. Hall</a>
44  */

45
46 public class IteratorComparator<T> implements Comparator JavaDoc<Iterator JavaDoc<? extends T>>, Serializable JavaDoc {
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48     static final long serialVersionUID = 1110218880817939318L;
49
50     // The comparator used to compare the elements of the two argument comparators
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private Comparator JavaDoc<? super T> _comp;
52
53     /**
54      * Builds an IteratorComparator that uses the given Comparator to compare
55      * the elements of an iteration.
56      */

57     public IteratorComparator(Comparator JavaDoc<? super T> comp) {
58         _comp = comp;
59     }
60         
61     /**
62      * Compares the contents of the two iterations. An element from each
63      * iteration is passed to the given comparator, and if they are not equal,
64      * the iteration that produced the lesser of the two elements is determined
65      * to be the lesser of the two iterations. If the elements are equal, then
66      * the next pair of elements if passed. If one of the two iterations is
67      * exhausted before a pair of unequal elements is found, then it is
68      * considered to be the lesser. If both iterations are exhausted before a
69      * pair of unequal elements is found, then the iterations are determined to
70      * be equal.
71      * <p>
72      * Neither iteration will be advanced past the point where an unequal pair
73      * is found, but the elements that were unequal will have been consumed.
74      *
75      * @return -1 if x < y, 1 if x > y, 0 if x == y
76      */

77     public int compare(Iterator JavaDoc<? extends T> x, Iterator JavaDoc<? extends T> y)
78     {
79         while (true) {
80             if (x.hasNext()) {
81                 if (y.hasNext()) {
82                     int i = _comp.compare(x.next(),y.next());
83                     if( i != 0) {
84                         return i;
85                     }
86                 }
87                 else
88                     return 1;
89             }
90             else
91                 return y.hasNext() ? -1 : 0;
92         }
93     }
94 }
95
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