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Java > Open Source Codes > net > sf > jga > fn > comparison > Greater


1 // ============================================================================
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// $Id: Greater.java,v 1.17 2006/01/08 00:52:25 davidahall Exp $
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// Copyright (c) 2002-2005 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.fn.comparison;
34
35 import java.util.Comparator JavaDoc;
36 import net.sf.jga.fn.BinaryPredicate;
37 import net.sf.jga.util.ComparableComparator;
38
39 /**
40  * Binary Predicate that returns TRUE for arguments <b>x</b> and <b>y</b> when
41  * x &gt; y. The comparison is performed using a comparator supplied at
42  * construction time, although a default comparator will be used if the nested
43  * Comparable class' default constructor is used.
44  * The behaviour of this class in the presence of null arguments is left to the
45  * implementation of the specific Comparator, however it is generally safe to
46  * assume that using null arguments will cause a NullPointerException to be
47  * thrown.
48  * <p>
49  * To serialize a Greater predicate, the comparator passed at construction must be
50  * Serializable.
51  * <p>
52  * Copyright &copy; 2002-2005 David A. Hall
53  *
54  * @author <a HREF="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
55  **/

56
57 public class Greater<T> extends BinaryPredicate<T,T> {
58
59     static final long serialVersionUID = 8666386929519645339L;
60     
61     // The Comparator used to compare elements.
62
private Comparator JavaDoc/*@*/<? super T>/*@*/ _comp;
63     
64     /**
65      * Builds a Greater predicate using the given Comparator
66      * @throws IllegalArgumentException if the argument is null
67      */

68     public Greater(Comparator JavaDoc<? super T> comp) {
69         if (comp == null) {
70             throw new IllegalArgumentException JavaDoc("Comparator may not be null");
71         }
72         
73         _comp = comp;
74     }
75
76     /**
77      * Returns the comparator in use by this functor
78      * @return the comparator in use by this functor
79      */

80     public Comparator JavaDoc<? super T> getComparator() { return _comp; }
81     
82     // BinaryPredicate interface
83

84     /**
85      * Given Comparable arguments <b>x</b> and <b>y</b>, returns x &gt; y.
86      *
87      * @throws NullPointerException if either argument is null
88      * @return x &gt; y
89      */

90     public Boolean JavaDoc fn(T x, T y) {
91         return Boolean.valueOf(getComparator().compare(x, y) > 0);
92     }
93
94     /**
95      * Calls the Visitor's <code>visit(Greater)</code> method, if it
96      * implements the nested Visitor interface.
97      */

98     public void accept(net.sf.jga.fn.Visitor v) {
99         if (v instanceof Greater.Visitor)
100             ((Greater.Visitor)v).visit(this);
101         else
102             v.visit(this);
103     }
104
105     // Object overrides
106

107     public String JavaDoc toString() {
108         return "Greater";
109     }
110     
111     // Acyclic Visitor
112

113     /**
114      * Interface for classes that may interpret a <b>Greater</b> predicate.
115      */

116     public interface Visitor extends net.sf.jga.fn.Visitor {
117         public void visit(Greater host);
118     }
119     
120     /**
121      * Greater predicate for use with Comparable arguments. This class exists
122      * as an implementation detail that works around a limit in the javac
123      * inferencer -- in all substantive ways, this is simply a Greater functor.
124      */

125
126     static public class Comparable<T extends java.lang.Comparable JavaDoc/*@*/<? super T>/*@*/>
127             extends Greater<T>
128     {
129         static final long serialVersionUID = 5187118104447673700L;
130         public Comparable() { super(new ComparableComparator<T>()); }
131     }
132 }
133
134
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