KickJava   Java API By Example, From Geeks To Geeks.

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


1 // ============================================================================
2 // $Id: Min.java,v 1.11 2006/01/08 00:52:25 davidahall Exp $
3 // Copyright (c) 2003-2005 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 package net.sf.jga.fn.comparison;
33
34 import java.util.Comparator JavaDoc;
35 import net.sf.jga.fn.BinaryFunctor;
36 import net.sf.jga.util.ComparableComparator;
37
38 /**
39  * Binary Functor that returns the lesser of two object arguments <b>x</b>
40  * and <b>y</b>. The comparison is performed using a comparator supplied at
41  * construction time, although a default comparator will be used if the nested
42  * Comparable class' default constructor is used.
43  * The behaviour of this class in the presence of null arguments is left to the
44  * implementation of the specific Comparator, however it is generally safe to
45  * assume that using null arguments will cause a NullPointerException to be
46  * thrown.
47  * <p>
48  * To serialize a Min functor, the comparator passed at construction must be
49  * Serializable.
50  * <p>
51  * Copyright &copy; 2003-2005 David A. Hall
52  *
53  *
54  * @author <a HREF="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
55  **/
56
57 public class Min<T> extends BinaryFunctor<T,T,T> {
58     
59     static final long serialVersionUID = 5803316056345309669L;
60     
61     // the comparator used to compare values
62 private Comparator JavaDoc/*@*/<? super T>/*@*/ _comp;
63
64     /**
65      * Builds a Less predicate using the given Comparator
66      * @throws IllegalArgumentException if the argument is null
67      */
68     public Min(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     // BinaryFunctor interface
83
84     /**
85      * Returns the lesser of two arguments, or the first if they are equal.
86      * @return the lesser of two arguments, or the first if they are equal.
87      */
88     public T fn(T x, T y) {
89         return _comp.compare(x,y) <= 0 ? x : y;
90     }
91     
92     /**
93      * Calls the Visitor's <code>visit(Min)</code> method, if it
94      * implements the nested Visitor interface.
95      */
96     public void accept(net.sf.jga.fn.Visitor v) {
97         if (v instanceof Min.Visitor)
98             ((Min.Visitor)v).visit(this);
99         else
100             v.visit(this);
101     }
102
103     // Object overrides
104
105     public String JavaDoc toString() {
106         return "Min";
107     }
108     
109     // Acyclic Visitor
110
111     /**
112      * Interface for classes that may interpret a <b>Min</b> predicate.
113      */
114     public interface Visitor extends net.sf.jga.fn.Visitor {
115         public void visit(Min host);
116     }
117     
118     /**
119      * Min functor for use with Comparable arguments. This class exists
120      * as an implementation detail that works around a limit in the javac
121      * inferencer -- in all substantive ways, this is simply a Min functor.
122      */
123
124     static public class Comparable<T extends java.lang.Comparable JavaDoc/*@*/<? super T>/*@*/>
125             extends Min<T>
126     {
127         static final long serialVersionUID = 210564993022120194L;
128         public Comparable() { super(new ComparableComparator<T>()); }
129     }
130 }
131
Popular Tags