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


1 // ============================================================================
2 // $Id: Between.java,v 1.13 2006/01/08 00:52:25 davidahall Exp $
3 // Copyright (c) 2002-2005 David A. Hall
4 // ============================================================================
5 // The contents of this file are subject to the Common Development and
6 // Distribution License (CDDL), Version 1.0 (the License); you may not use this
7 // file except in compliance with the License. You should have received a copy
8 // of the the License along with this file: if not, a copy of the License is
9 // 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
33 package net.sf.jga.fn.comparison;
34
35 import java.util.Comparator JavaDoc;
36 import net.sf.jga.fn.UnaryFunctor;
37 import net.sf.jga.fn.UnaryPredicate;
38 import net.sf.jga.util.ComparableComparator;
39
40 /**
41  * Unary Predicate that returns TRUE when its argument is between two given
42  * values. By default, the range is inclusive: a constructor is provided that
43  * allows client code to supply two predicates that can create exclusive ranges.
44  * The comparison is performed using a comparator or a pair of functors supplied
45  * at construction time: a default comparator will be used if the nested
46  * Comparable class' default constructor is used.
47  * The behaviour of this class in the presence of null arguments is left to the
48  * implementation of the specific Comparator, however it is generally safe to
49  * assume that using null arguments will cause a NullPointerException to be
50  * thrown.
51  * <p>
52  * Copyright &copy; 2003-2005 David A. Hall
53  *
54  * @author <a HREF="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
55  **/
56
57 public class Between<T> extends UnaryPredicate<T> {
58     
59     static final long serialVersionUID = 7520704443234013748L;
60     
61     private UnaryFunctor<T,Boolean JavaDoc> _ge;
62     private UnaryFunctor<T,Boolean JavaDoc> _le;
63
64     /**
65      * Builds a Between predicate that returns TRUE when its argument is between
66      * its two arguments (inclusive). The given comparator will be used to
67      * compare values.
68      * @throws IllegalArgumentException when either argument is null or when
69      * lo &gt; hi
70      */
71     public Between(T lo, T hi, Comparator JavaDoc<? super T> comp) {
72         if (lo == null || hi == null) {
73             String JavaDoc msg = "a pair of values is required";
74             throw new IllegalArgumentException JavaDoc(msg);
75         }
76
77         if (comp.compare(lo,hi) > 0) {
78             String JavaDoc msg = "lo value must be less than hi value";
79             throw new IllegalArgumentException JavaDoc(msg);
80         }
81
82         _ge = new GreaterEqual<T>(comp).bind2nd(lo);
83         _le = new LessEqual<T>(comp).bind2nd(hi);
84     }
85
86     /**
87      * Builds a Between predicate that returns TRUE when both of the given
88      * predicates return TRUE for the same argument. This version of the
89      * constructor is provided to allow finer control over the comparisons
90      * performed.
91      */
92     public Between(UnaryFunctor<T,Boolean JavaDoc> lo, UnaryFunctor<T,Boolean JavaDoc> hi) {
93         if (lo == null || hi == null) {
94             String JavaDoc msg = "a pair of predicates is required";
95             throw new IllegalArgumentException JavaDoc(msg);
96         }
97
98         _ge = lo;
99         _le = hi;
100     }
101     
102     // UnaryPredicate interface
103
104     /**
105      * Given argument <b>x</b>, returns TRUE if x is between lo and hi.
106      *
107      * @return lo &lt; x &lt; hi
108      */
109     public Boolean JavaDoc fn(T x) {
110         return Boolean.valueOf(_ge.fn(x).booleanValue() && _le.fn(x).booleanValue());
111     }
112
113     /**
114      * Calls the Visitor's <code>visit(Between)</code> method, if it
115      * implements the nested Visitor interface.
116      */
117     public void accept(net.sf.jga.fn.Visitor v) {
118         if (v instanceof Between.Visitor)
119             ((Between.Visitor)v).visit(this);
120         else
121             v.visit(this);
122     }
123
124     // Object overrides
125
126     public String JavaDoc toString() {
127         return "Between";
128     }
129     
130     // Acyclic Visitor
131
132     /**
133      * Interface for classes that may interpret an <b>Between</b> predicate.
134      */
135     public interface Visitor extends net.sf.jga.fn.Visitor {
136         public void visit(Between host);
137     }
138
139     /**
140      * Between functor for use with Comparable arguments. This class exists
141      * as an implementation detail that works around a limit in the javac
142      * inferencer -- in all substantive ways, this is simply a Between functor.
143      */
144
145     static public class Comparable<T extends java.lang.Comparable JavaDoc/*@*/<? super T>/*@*/>
146             extends Between<T>
147     {
148         static final long serialVersionUID = 4385771596777515479L;
149         public Comparable(T lo, T hi) { super(lo, hi, new ComparableComparator<T>()); }
150     }
151 }
152
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